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Posted By: racprops Building high MPG Motor for a 93 Vhevy Van - September 10th 2009 4:23 pm
OK Here is a deep question about cams…

I am building up a 1993 Chevy Van with a Chevy 350 motor.

I am building what I hope will be a Van that can get 25+ MPG at 75 MPH.

I am building a engine specially for low RPM power and I need a low torque RPM Cam, one that peaks at 2200 RPM, and with 4 degrees should reset for 1800 to 2000.

I have what I think is a good cam many call it the peanut cam.

It is out of a 1990 Caddy Fleetwood Limo and according to the spects made 270 FP of torque at 2200 RPMs.(anyone got the spect on this cam??)


So what do any one think of this cam and is there a better low RPM Cam to be had.

Also what about Rhoads lifters??

To also fill you in: The motor is a .030 bored out with Keith Black D shaped Pistons, and the early Vortec type heads with small ports and valves and the swirl heads.. cleaned up right..

And I plan on running a TPI Intake on it…

Transmission will be a 4l60 and behind it a 3 speed overdrive with only 3 and 2nd gears and the OD.

Making it a 12/14 gear set up, mainly a under and over drive system, 2nd gear working as a underdrive to fix the tall rear end and over drive to add to the stock OD for even lower engine speed.

The idea is to run at around 1500 RPM at 75 MPH it double OD.

So commits?

Rich



Posted By: Superbeast Re: Building high MPG Motor for a 93 Vhevy Van - September 10th 2009 4:34 pm
There is a guy in Canada that did the 2 trans deal and gets 20MPG with a blown big block.

Rhodes made good products in the past. I would imagine they still do.

I always recommend an RV type cam for any van motor. They are designed for torque to get the vehicle moving, and have a good RPM range.
Posted By: matchstickBGV Re: Building high MPG Motor for a 93 Vhevy Van - September 10th 2009 4:49 pm
wow, you sound you know your stuff man! I like the sound of this project. anything like an RV cam like ken said. what kind of gear will you have in the rear end, something like a 3.02?
Posted By: CatFish Re: Building high MPG Motor for a 93 Vhevy Van - September 10th 2009 5:56 pm
The '90 Caddy would be a roller cam I believe. I would keep the factory rollers.
The factory roller cam "peanut version" would be (intake/exhaust) 179/194 degrees duration (@.050"), 0.350"/0.385" lift and 109 degrees separation.
Look up part # 10088155.

It's no hot rod but if you use it you can cheat fate with some higher ratio rockers. A little more torque at the same rpm and it shouldn't hurt your mileage.
An RV cam will be (intake/exhaust) about 195/205 degrees duration (@.050"), 0.430"/0.460" but should hold the 109 or 110 degree separation. (I'm guessing).

One more idea: Stay away from large tube headers as they will move our torque peak higher, some small tri-Y's would be good.
And don't forget to wrap those little tube headers.

Been a long time since I played with a GM.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 11th 2009 1:35 pm
“The '90 Caddy would be a roller cam I believe. I would keep the factory rollers.
The factory roller cam "peanut version" would be (intake/exhaust) 179/194 degrees duration (@.050"), 0.350"/0.385" lift and 109 degrees separation.
Look up part # 10088155.”

That sure sound like the right cam…roller and small.

“It's no hot rod but if you use it you can cheat fate with some higher ratio rockers. A little more torque at the same rpm and it shouldn't hurt your mileage.”

I already bought a set of roller tip rockers for it, I was planning on advancing it by 4 degrees by a true roller chain set. What do you think that will do?

Rich
Posted By: CatFish Re: Building high MPG Motor for a 93 Vhevy Van - September 11th 2009 6:00 pm
BTW Rich, good luck with this project.
4 degrees is quite a bit and you'll already have an under drive, you'll run past the torque peak pretty quick. If I were you, I'd degree the cam with the stock set-up during assembly, compare that to the design specs, and then decide. You may be a degree or so advanced/retarded already, as the cams, gears and chain can sometimes be. You could also compare stock rockers to the roller tips in relation to valve lift.
What's your plans on the ECM programming?

Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 11th 2009 8:59 pm
you want some serious low end torque?? if you aren;t running much more than 4500rpm, then bolt on a set of 305 heads. the smaller intake runners in the heads massivly increase the air velocity causing greater swirl as well as an almost forced induction on the bottom of the stroke. you only need to round off the edge in the combustion chambers to prevent hot spots. stock dished pistons on a 350 will give it about a 9.1 to 1 compression ratio. the vaccum signal if you're running a carb will be SO efficient that you can detune the carb and still get awesome performance. I have seen this setup in a large truck get 29-30 mpg on the highway. I used to get 27 mpg on highway in my 85 Monte SS with 305 and q-jet. If you have TBI, switch to a 305 TBI unit. the goal to economy is burning everything in the chamber. thee high velocity and the small chamber will greatly increase that efficiency by burning more of the fuel. hence, you get more power on the same gas which results in less throttle.that high velocity also generates some massive low end grunt for towing. only downfall is.. above 4500 RPMs, they start to fall off on power and air efficiency.
Posted By: josh_performanceinc Re: Building high MPG Motor for a 93 Vhevy Van - September 11th 2009 9:20 pm
I did this to my big blue van. I'm running 86 monte 5.0 HO heads.

Swimm.... I didn't change the TBI unit though... I was under the impression that the computer "brain" controls the pulse on the injectors and was hoping the emission system would compensate for the resulting rich burn. Bill in our club had a chip reprogrammed for his to lengthen the pulse when he did some work to his motor. Well anyway, once in a while I get the emission light coming on. I guess it might be a victim of that. It also has an off idle stumble.... But she pulls strong alright, I'll attest to that. Pulls a car trailer complete with full size car like it wasn't back there at all.

Anyone have a 305 'puter and/or chip?
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 2:18 am
You can get a fuel pressure regulator kit that makes yours adjustable. or.. you can just modify it yourself. reducing or increasing the pressure will change how much fuel comes out per pulse width. this might fix your problem. I talked about the TBI due to the smaller bore size. the injectors themselves are the same i believe.. only times i've done this or seen it done was with carbs. far easier to turn a few screws than computer swapping and chip burning.. lolol.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 3:06 am
Thanks.
With a new TIGHT true roller chain set it will be what I set it for.
I am getting a lot of info and also on a chevy group adn they are saying that cam is a limp string adn I really should get a better cam.

But the cam makers all shift the RPM range up to give more HP, any know of a good cam that torques at around 2000 RPM.

Thr Crane Roller Tip are suppost to be the same as non rollers.

Well I though I had bought a Romulator but after 10 days and no show I started a protest with paypal...

I was going to roll my own...

Rich



Originally Posted by CatFish
BTW Rich, good luck with this project.
4 degrees is quite a bit and you'll already have an under drive, you'll run past the torque peak pretty quick. If I were you, I'd degree the cam with the stock set-up during assembly, compare that to the design specs, and then decide. You may be a degree or so advanced/retarded already, as the cams, gears and chain can sometimes be. You could also compare stock rockers to the roller tips in relation to valve lift.
What's your plans on the ECM programming?

Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 3:08 am
Where can I get the refulator kit??

That will be a help...

Rich


Originally Posted by swimmster
You can get a fuel pressure regulator kit that makes yours adjustable. or.. you can just modify it yourself. reducing or increasing the pressure will change how much fuel comes out per pulse width. this might fix your problem. I talked about the TBI due to the smaller bore size. the injectors themselves are the same i believe.. only times i've done this or seen it done was with carbs. far easier to turn a few screws than computer swapping and chip burning.. lolol.
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 3:57 am
this shows you how to modify your own,

http://members.shaw.ca/betterthanyoutoo/how-to/fpr/fpr.htm

nuther article

http://www.thirdgen.org/tbi-afpr

Here's a new one..
http://www.streetperformance.com/part/jet-performance/fuel-pressure-regulator/61814-61500.html

Posted By: josh_performanceinc Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 2:31 pm
Awesome Swimm.... tanks! yay
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 4:47 pm
You should be able to drop your fuel pressure and get rid of your rich condition and stumble without the new computer or chip. I'd find a 305 throttle body though. the air velocity will really wake up the fuel mixture and you can use less fuel cause you will burn much more of what's going in the cylinder.


On a side note to the economy aspect of building an efficient engine. if you have headers, you can experiment with swapping your exhaust rockers with 1.6:1 factory rockers. they are out there.. just gotta remember what they were on or part numbers to order.

If you wanna be real different and you're gonona pop for a new cam, consider what they call a "4-7 swap" cam.. it changes the firing order and swaps the 4 and 7 cylinder in the order. this smooths out the motor believe it or not. it also gives it kind of that ford mustang 5.0 sound. TONS of drag racers running chevies run these cams for increased efficiency. why they are not much more widely available, i dunno.. only different setup you have to do is just once installed, swap the 4 and 7 plug wires at the cap.
I don't have all the details, but Alien in Canada has 2 tranny's slaved together, and by playing with the both of them, he gets 28 MPG @ 80 MPH.... He also has higher ratio's for Drag Racing and shift available...

OH yeah, the motor is a Blown 454

[Linked Image]
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 5:21 pm
Also over on the Third Gen thay are doing late model: a sequential fired motor and 4l60 control in one shot onto the older engines...

http://www.thirdgen.org/techboard/diy-prom/353405-sequential-injection-gen-i.html

Just in case your interested.

Rich
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 5:22 pm
A BLOWER!!!IN A VAN??? STOCK DOGHOUSE??

INCREATABLE!!!

What tranies does he use?

Rich
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 5:25 pm
OK Very interesting so where do I find a 4/7 cam and do they do them in stocker cams...

RIch
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 9:14 pm
interesting article on the reason for the birth of the 4-7 swap cam. evidently they are a bit more than a high end cam. most common manufacturer is Lunati. they can seemingly make you anything you want. Interesting how this really came about due to factory design issues that were trying to be corrected for high performance use. I have always had excellent luck with calling Lunati or Manley and talking to a tech. explaining to them exactly what you have and what you want to do. They will give you excellent recommendations on cam specs to idealy suit your needs with the equipment you are working with. they will even recommend equipment to get you to your goal if what you have is not compatible with the result you are looking for.

http://forums.chevyhiperformance.co...on/4-7-lobe-swap-cam-question/index.html
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 12th 2009 10:57 pm
Oh I remember about the problem of the Rooads Lifters and knock sensors and that they really fade out at the low rpm I want to use.

What about the old adjustable cam timing gear set, they were spring loaded to change the cam timing ??

I am trying to have low RPM power and then run normal at higher RPMs...

Any one ever hear of Power valves?

I have a 305 TB in a 87 Van that needs an engine...heck I might just pull those heads and build them...

OR a wild idea, build the 305 with a 400 crank and end up with a strocked 342 (or something...)

Long strock small bore?


Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 13th 2009 5:35 pm
man.. I used to know all the bore/stroke combos out there.. what would work with what, etc.. lol..

I know if you go with 305 heads, forget anything above 4500 rpms.. power starts dropping like a rock.. I think you may be heading towards an excellent breathing 400 plus hp motor with good everything on thru to 6000 rpms, and going with a gear vendors over/underdrive unit and then throwin in some 3.08 rearend gears if you can find some beefed up enough to handle the strain. Lot of factors going against good economy. lots of parasitic losses in a drivetrain. most automatics can easily burn up 40-60 hp just turning everything and maintaining pump pressure. LOTS of compromises in a high horsepower yet economic engine drivetrain combo..
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 14th 2009 2:30 am
OK Have you done the 305 TBI trick adn have you done the 305 heads on a 350??

Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 14th 2009 3:00 am
I have had 305 heads on a 350. you gotta clean up the sharp edges on the combustion chamber to get rid of potential hot spots for pre-ignition. I used bone stock 87 305 heads from a monte carlo application on my 94 GMC pickup. converted it to a Q-jet. I was getting 28 mpg on the highway at 70mph on long trips. MASSIVE amount of low end grunt. hard to not spin the tires with no load. used to haul the race car like it was invisible. would go up hills like they were flat open road. headers help with this setup too. course, they help with any setup.

the 305 TBI works as good or better with an adjustment of the pressure regulator. If i remember right, the friend who had that setup reduced the pressure and had more gains. the air intake velocity is sufficient to further atomize the fuel into the air and create a better mixture. you get more power with less fuel. the 305 TBI body has smaller diameter bores which effectively helps out in the air velocity department. Your vacuum level in the intake will go up a bit too. I never played with aftermarket cams for the truck. I am sure though that a call to a manufacturer will get you something that could make the setup work even better. If you're going to throw alot of money at this issue, find a set of vortec heads for a truck as they are cheaper, have the exhaust ports ported to flow better as the intakes are the same as the performance vortec heads. vortec heads have efficient intake runners ad high swirl combustion chambers that make them a pretty efficient head design. You can get some gains in economy with ignition parts too. get a high voltage coil and bump up your plug gap. get a shim kit for your distributor gear so you can have highly accurate timing.
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 14th 2009 3:17 pm
Hey hey.. I apologize for not totally comprehending your first post.. i fully read it the first time, then promtly forgot what you were using for a setup. the TPI intake may be a waste on the vortec heads. the runners will be far too long and your D pistons will just be a waste. yes, looong runners will increase velocity, but that length of runner will cause the fuel droplets to start pooling together by the time they reach the cylinder and this pretty much negates the swirl heads as you're back to OEM efficiency and not burning as much of the mixture as you could be. the short yet small intake ports on the 305 heads makes for a nice quick burst of airflow into the cylinder without the fuel droplets having time to come back together. Leaving a very rough, as cast finish on the intake ports helps with keeping the air moving with turbulence to help keep the mixture as atomized as possible. smooth ports only really helps when you're in the 6-8,000 RPM range making TONS of power.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 14th 2009 6:37 pm
I am unsure what your thinking...

But I am still stuck runming a TBI unit so I am looking to tighten it a little before I swap out the old motor and switch to a TPI unit.

So I am working on both.

I have a 87 305 in a another Chevy Van that is knocking...So it is a dead motor.

So I have a 305 TBI unit and a pair of 78 Heads if I want them.

Did they ever make a Vortec 305?

A stock TPI is port injected so the runners run dry...

So how will it work with the 305 heads?

Rich



Originally Posted by swimmster
Hey hey.. I apologize for not totally comprehending your first post.. i fully read it the first time, then promtly forgot what you were using for a setup. the TPI intake may be a waste on the vortec heads. the runners will be far too long and your D pistons will just be a waste. yes, looong runners will increase velocity, but that length of runner will cause the fuel droplets to start pooling together by the time they reach the cylinder and this pretty much negates the swirl heads as you're back to OEM efficiency and not burning as much of the mixture as you could be. the short yet small intake ports on the 305 heads makes for a nice quick burst of airflow into the cylinder without the fuel droplets having time to come back together. Leaving a very rough, as cast finish on the intake ports helps with keeping the air moving with turbulence to help keep the mixture as atomized as possible. smooth ports only really helps when you're in the 6-8,000 RPM range making TONS of power.
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 14th 2009 7:56 pm
MOST TPI systems were on 305 engines.. make sure yours matches. if you install a 305 TPI on a 350, you will need a custom burned EPROM. For what you want to do, in the RPM range you want to use, the 305 TBI will work excellent. use that and the 305 heads and you'll have tons of low end torque. the shorter runners of the TBI manifold will let you breath better. than the TPI. your 350 suckin thru long ass 305 TPI runners will cause more harm than good. 305 vortec heads.. hmmmm.. I don;t THINK they made them, but i could be wrong. if you plan to use vortec heads, make sure your piston domes don't hit. even 350 vortec heads with so much as flat top pistons generates 9 to 1 compression. if you have a slight dome, then you're lookin at 92 octane MIN.. there goes your gas savings.. lol.. There's alot of ways to do this.. you just have trade offs on most of them.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 3:02 am
Please show my the front of your engine so I can see if I can use my stock belt set up..

Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 11:19 am
that was quite a while ago. no longer have that. most all small block chevy front accessories will swap over except the LT1-4 stuff. even 4.3 v6 stuff will swap over. even if you;re converting from an old multi-belt system to a factory serpentine system.

this is the llast pic i took of the car motor before i got rid of all that stuff.. swapped over to vortec heads. note the vertical intake bolts. when it comes to front end parts, I generally make my own mounts and usually will use a serpentine or multi groove belt. i just get everything in place and then measure for the belt size. NAPA will sell you belts based on length. This car here, I had small alternator, remote resevoir power steering and all the brackets were done for an under mounted mini AC compressor.. one that you find on all the newer GM cars.

[Linked Image]

For what it's worth, I used to run this motor at 12.92 in the 1/4 mile. car weighed 3100 lbs. It was a flat topped piston, std. bore cylinder and the stock 97 vortec truck cam. L31 was the OEM number for the cam. was the cheapest 450 hp I ever built. vortec heads, headers, edelbrock intake, holleey 750 and speed-pro flat top pistons.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 2:34 pm
The Van is a special problem as the Alternator and A/C have to be mounted high on top of the engine right on top of the valve covers...

I am only eyeballing it but worry that the belt tensor will be in the way.

I was hoping to see how and what belt set up you had used on that Van.

A normal car has a lot more room and I could rerig it.
(I did a Cleaven 350 Ford into a 67 Cougar XR7 and a 350 olds into a 78 Van.)

Rich
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 2:40 pm
Also I talked with a couple of people about using a 305 heads on a 350.

They say NO WAY!!!

So question is have you done this with a swirl intake early Vortec type of heads say a 87 on a 93 350??

Sorry to bug you on this but I can not afford the costs nor the time to do this engine a couple of times... so I like NASA really need to be sure before I lunch it.

I take it cutting the 305 heads out to match the 350 gaskets will cure any sharp edges and open the chamber a little as well lowering the compression ratio too.

RIch
Posted By: wookee Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 3:35 pm
I am running a 203/212 duration cam in the stock 350 "crate" engine in my Early Chevy right now.
I put close to 70,000 mile on this engine with the stock cam in this engine.
It only got 9 miles to the gallon.
With this cam not only did the performance of the engine "wake up".
The gas milage increased signifacantly.
11 around town 16 on the hiway.
On the cheap stuff.Driving the van like i stole it......

I have been watching this thread.I have an 89GMC with a 350/700R4 trans TBI injected.
It only gets 11 MPG.
I have a H.O. 350 crate engine setting here waiting to go in the GMC.
I am on the fence weather to run a carb or fuel injection.
I just feel like the puter will not allow the egine to wind out as tight (5 grand first gear shifts)as the carb HEI set lets the engine do......

This low end torque cam made this egine/van really nasty light to light

.........Wookee
I guess I am doing good with my 78, stock 305 2BBL with 2:73 gears..stock exhaust with the pizze platter sized original Cat.

I am getting around 17 per gallon @ 55 mph pulling the trailer, about 15 at 70 MPH
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 7:47 pm
Well I am being a bit piggy, my van does get 17.73 MPG at 70 MPH.

I want more....

I think the computer controled FI either TBI or TPI is the best way to go...and will give it to me.

I am getting a Romulator that with my Laptop will let me tweak and fine tune the Van like a $3000.00 dyno tune and blueprint job...and I can do it over and over again and again...

The problem with carbs is the get messed up at low RPMs and will dump fuel with you get low vacuun...

And timing control...all machanial..very limited range I have seen a computer controled system go from 40 BTDC to 40 ATDC in a split second, and knock sensors will and can save your motor...

Add in that the average life of Carb motors was 100,000... but I have seen FI motor easly do 200/400,000 miles... My friend Jon has 2004 Ford F250 Van with 400,000 on it, and it still runs good.

I think because of the delay in starting which allow oil pressure to get up and no shot of gas pumped in my the accurator pump every start up...

I would not go back to a carb and spark system unless a Nuke was air bursted and burned out the clips...until then give me FI.

My 2 cents worth.. as a 61 year old car nut...

Rich
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 8:29 pm
Sadly I fell out of love with computer controled cars with the 96 and newer models, those OBDII system are much harder to tweak...

Rich
Posted By: Superbeast Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 10:10 pm
So all of this is to improve from almost 18 MPG? Question for you, and please don't take this the wrong way. What is your projected rate of return on this whole endeavor? Yes, you may be able to get it up to 20 or 25 MPG, but at what cost. So far all the stuff you have been talking about seems rather expensive, unless of coarse, you already have it all, but with the 2 to 7 MPG increase, will it ever pay for itself? The only reason, I'm asking is because it seems like a big expense, and a lot of work without much return.
You can get almost 10 percent increase by making the rear tire 2 sizes bigger or there abouts...

All you have to do is wait until the rears wear out
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 15th 2009 11:26 pm
The tire size is funny...

Why, well I have 130,000+ on a chevy motor, a stock Chevy motor..

I had a 87 I WAS going to fix up the one with the knocking 305 that I may use for parts like the 305 injectors and the heads...so I already have the 90% done 350...

I am 61 years young and figuer to get this rebuilt so I cruse around in it for the next 10 to 20 years...

And it is something I have been trying to do for the past 20+ years as well.. so might as well do it...

Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 16th 2009 1:05 am
Whoever you're talking to about the 305 heads being a no no obviously did it wrong. MANY of the car mags did this swap with excellent low end results.. as for using a carb, you will NOT get a low vaccum signal with this setup. the air velocity caused by the big bore and the small intake ports creates an excellent vaccum signal at the venturi's which means you get to de-jet the carb and turn down your idle mixture screws. This all causes MUCH better atomization of the fuel mixture. air speed in a TPI, TBI or carb is ALWAYS a good thing.. say with a Dual plane manifold for instance.. some cylinders tend to draw more or at least recieve more mixture than others. the increase in velocity helps aleviate much of that issue because the air is flowing so much faster. typical A/F ratio is between 14 and 16:1. the more you can atomize the fuel, the higher you can get this ratio and still get the same power. If you could get the fuel to turn into a straight up gas ie. FUMES, you would be burning a very small amount of fuel with the same power. one of the MOST fuel efficient carbs going is the Quadrajet. the primaries are smaller than most any 2 barrel carb out there. when tuned properly, I have gotten 27 mpg out of a 305 on the highway. I have gotten 22 mpg on a 350 with a q-jet in a 94 GMC pickup.

The only vortec heads i have used were brand new 97 year truck casting vortec heads. they are identical to performance casting vortecs except the exhaust valve seat is hardened and the material around the seat a bit thicker.. port work there makes them as good or better than the more expensive performance ones. depending on what YEAR of heads you use will detrmine what manifold you use. up to 1987 was one intake, then 87 to 95ish was another. 96 had the vortec which will never bolt to an older intake or vice verse. then the odd variations like the TPI and the LT1 intake.

Problem is, if you want power, you trade efficiency and vice verse. you can't have them both.. just the best compromise you can find. bang for the buck? I still swear by 305 heads with the chamber edges rounded over slightly.. just enough to get rid of the sharp corners. on top of a stock 350 with factory dished pistons to keep the compression down to 9:1. set of headers, a q-jet intake and carb, and a finely tuned distributor.. high output ignition coil for HEI and gapping the plugs out towards .050 to get a large spark to burn everything. that setup, done right, and I can get you 25-26 mpg in your van.. given the right rear end gears.. 3:08 gearset would do you real well with a slightly taller tire and just a 700r4 overdrive trans. oh, and shaving some lead off the right foot helps out too.. consulting with a REPUTABLE cam manufacturer with which ever combo you end up deciding on would yeild you possibly even better returns. when it comes to your computer program, unless you have a flashable OBD-II system, you're going to be stuck burning EEPROMS unless you spring for the module that you can plug in tot he prom socket and write maps on the fly.. sort of.. you can;t change the maps while running.. you have to create the map, load it to the module and see if it does what you wnat.. if not, you have to make another map and load it up again.. nothing I know of, as of a few years ago, has the ability to change map info on the fly in an OBD-I system. today though, I could be wrong. new things come out all the time. There is also, out there somewhere, a HOME BREW digital fuel injection stand alone system you can buy in a kit form and build it yourself. supposed to be highly programmable and can be done on the fly with laptop.


while i'm thinkin about it.. the TPI system is not the kind of injection system you would like to believe it is. the injectors on a TPI system do NOT fire individually. they fire the same as a TBI.. one bank, then the other bank.. Look at the wiring diagrams for all the TPI systems.. all the injectors go to 2 terminals on the computer. left and right bank. This is HORRENDOUS when it comes to atomized fuel. you have an injector firing 3 times at the valve before it ever opens and sucks in a bunch of puddled fuel..


Ok.. my brain's gettin fried remembering all this stuff..
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 16th 2009 1:06 am
Also.. any truck front accessory mounts will work in the van..
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 16th 2009 2:35 am
I know about the batch firing... and am considering a newer computer for it...

Thanks for the feed back.

I am really looking at the 305 heads...

As I know that torque really gets you up and gone.

I have a 2000 Ford with a 4.6 that hits it rev limiter at 4800 and really runs out of breath at 4000. (did a dyno and saw it in real life...)

BUT that little 4.6 is nearly as fast and hot roddy as any stock 350 I have owned...perhaps faster...

It is a low RPM torquer...

And I have never owned a hot rod, I have had Studabaker Golden Hawks with 160 Speedos, and torque 289s, 65 Mustangs with 260s, 67 Cougar with a 289 then I swaped a 352 into it, a 79 Camaro with a 350, and so on...

I also had a 98 Caddy Cateara with a 6200 redline that was rated as a 300 hp out of a 3 Lt V 6.

My wifes Toyota with a 1.6 Lt would beat it across the cross walk, the Caddy had no take off...dual as dish water on take off a kid, on a 10 speed was faster...

Once launched it took off...

No bottom end, so give me torque...

Rich


Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 17th 2009 3:03 am
Wow I have found four to five other car sites that say the same thing: 305 heads on a 350 makes a torque monster...

I am a little concerned with the higher compression and will need to check out the heads I have and as it is on a truck I am hoping for the 58CC heads not the 54 CC heads, and that the 87 Van got the swrill port models as well.

I am thinking that if I open them up a little to match the 350 bore I can drop the compression down to a near Reg gas burner...

So I understand my peanut cam is a touch too winpy, suggestions for a slightly better cam?

Rich

Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 17th 2009 3:05 am
Oh with the 305 TB injectors: what pressure or pressure reg do I want and will my stock pump push high enought to run these??

I like getting a vacuum controled pressure reg as it should be better for MPG.

Rich

Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 17th 2009 6:12 pm
Well the Hot Rodders over on a Chevy Site are blowing me off...

If it don't run 3500 to 7000 they can not and will not think of a low RPM motor is even capable to run...


Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 18th 2009 12:44 am
lolol.. yeah.. the hot roders don;t want to talk about anything below 3500 rpm.. lolol..

TBI pressure regulators are built into the Throttle Body.. there are kits to make it adjustable which I recommend with the setup.. there's links here somewhere that show how to make your own adjustable. All your other stuff in stock form should be just fine.. your 350 engine computer will have a longer pulse width on the injectors, but being able to turn down the pressure will lower the amount of fuel going thru each pulse. no need to change to 305 computer, etc.. I don;t have a cam recommendation for ya as i never really got into that. too many variables.. I always just called the tech lines and gave them the rundown on what i had for parts and what my goal was.. never got a bad cam decision. As for compression.. if you have stock dished style pistons, your compression will be about 9.2:1. If you have anything beyond stockers, then you'll have to do some work. There's some info sites out there somewhere that show ya how to calculate your compression ratio using specs from certian head gaskets.. some are MUCH thicker than others. you can make up for some compression with the thicker gaskets. You've gotta be careful about opening up the chambers as you could run into the water jacket or make a pretty thin spot which will get hot.

If you have TBI already, your stock pump will be more than fine. TBI typically uses around 12-14 psi fuel pressure.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 18th 2009 2:52 am
I was thinking I would remove the stock pressure reg and add one that also used Vacuum to help control it..like the ones on the port injectors..

But I think I will need a adjustable one and most likely that means going to a after market model..

Rich

Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 18th 2009 3:06 am
the TBI one is vaccum controlled.. there;s a port in the TBI casting that feeds it direct manifold vaccum.. and remember, there's the links here that show you how to make your regulator adjustable.. same as the aftermarkets..
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 18th 2009 3:32 am
OK I missed that..of course it is internal...

Rich
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 19th 2009 12:24 am
Well after hours of carefull research I found two possable great cams, GM Factory only to learn thay are no longer for sale...

Any one know where I can get cam number 10066049 or 14093643

The first one is from a 88/89 Camaro and the second one is called a L98 Corvette and IROCK Camaro..
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 21st 2009 12:55 am
have you looked into what they call the LT4 hotcam? the profile is available in other than LT1 cam format so you can get the profile on cams for regular GM blocks. Also.. have you given any thought to the engine simulator programs? Desktop Dyno has proven time and again to be incredibly accurate.. Hotrod magazine says to deduct about 5% on the horsepower ratings, but otherwise nearly spot on.. the last one i had, had EVERY cam profile you could find,. listed by manufacturer and model numbers.. I built my last race car motor in Desktop Dyno and it gave me 428hp and 397ftlbs torque.. timeslips and car weight confirmed according to the HP calculators I was at 425 hp and 390 torque. that was putting some rather bizzar combos in the computer. have to look and see if i have my old copy layin around.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 22nd 2009 11:49 am
After much talk on these boards and with engine and cam makers…

I find there is no magic motor I can build, in fact I already have a motor with the peanut cam, my stock van motor has the same power and torque as the caddy model did.

OUCH…

It would be a slight improvement as in a fresh built motor but no real improvement.

OK I am giving a 383 very hard look.

I still want a mild cam, I still want a low RPM Motor, but a stroked 350 will give me more torque and HP even keeping things mild.

So if I run a stock to a TPI 350 Cam will things work? Can I stay with the 350 injectors as I am NOT building a hot rod…will a slight tune to the ecm cover the change?

I am hoping the 383 will not get worst MPG VS a 350 built the same way…

I am hoping a 383 due to its bigger torque will in fact get better MPG pulling a Van.

And combos do I want?

And what do I not want?

Thanks guys.

Rich



Posted By: gopher Re: Building high MPG Motor for a 93 Vhevy Van - September 22nd 2009 1:12 pm
I put 302 heads on my 351 ford saved gas and whent like stink
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 22nd 2009 3:34 pm
I'm tellin ya.. a 350 with 305 heads, will make a torque monster.. if you're just towing, then this is the way to go.. you'll likely never see the high side of 4500rpms anyways in your normal driving, so... a 383 is going to suck more fuel.. the more cubes of air you use, the more fuel you need to back it up.. You can put 1.6:1 rockers on the exhaust to help the flow outward as well as some headers.. If i had to build another motor JUST for towing and mileage, that's what it would be.. unless you're goin racing, a 383 is a bit overkill. you will for sure need a different cam to utilize the added cubes.
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 22nd 2009 11:40 pm
I hear you but even engine builder I know say that is totaly crazy, and will not work, a) because it will need Jet Fuel to run with the compression ratios, and the chamber is not alined with the bore and it hardly takes any maching to hit water...

And with my swirl port heads they are all ready smaller...

Rich
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 23rd 2009 3:42 am
Your engine builder is insane.. the bore centers are exactly the same.. and if you have stock pistons, the compression is fine.. as i stated above. This has been done countless times, both superchevy and hot rod mag did write ups on it and all the mods to the heads including the chambers. no offense, but your engine builder is a quack.. the chambers are perfectly aligned with the bores.. only smaller.. and all you have to do is round off the chamber edges.. you're not taking large sections of metal out.. just rounding them off. wouldn't mind conversing with your engine builder. You should see some of the things the pro-mod race car guys do with 305 heads... all the small block chevy stuff is the same.. only the bores are smaller.. nothing is shifted.. it;s all basicly the same casts.. same blueprint..
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 23rd 2009 5:39 pm
Well I just searched both sites and can not find any articles on them...

Got links?

Rich

Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 24th 2009 1:35 am
they're oooooooooold articles.. got the magazines somewhere.. have to do some research.. should be tons of google info..
Posted By: racprops Re: Building high MPG Motor for a 93 Vhevy Van - September 24th 2009 2:08 am
Well my auto wreaker friend use to race and he said it works on a race car with racing fuel and even then they had to retard the timing and on the street retard even more...

He said he has done them and would never think of driving a street car with that set up...

The biggest problems are how shroded the valves are and how high the compression will be.

Rich

Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 24th 2009 2:59 am
well.. prob here is you're talking to a race car guy.. they are NOT for high performance.. we were talking economy and low end grunt.. the race car guys will talk down about this all day long cause of their limitations on the high end.. the sprint cars and oval track cars have a 305 cu/in limitation so they have done WONDERS crankin up power on a 305.. ALl the complaints about timing, etc are cause they either used the super small 53CC chambered heads with their flat top pistons which gives you 10.5 and up compression.. that is a definite for race fuel. the larger much more common 56 and 64 cc chambered heads are where the gains are for a 350. the other pre-ignition issue comes from these guys not prepping the heads by chamfering the chamber edges. I also read about carbon build up on the quenching area.. this was because they didn't change the fuel system, and were running rich..

Anyways.. I'm clearly wasting my time here.. you;re gonna build it how you want to build it and listen to who you want to listen to.. that's fine.. just trying to tell you what info is out there and that there's an aweful lot of incorrect info or bad results from incorrect application. the valve shrouding is not even an issue until you're up around 6,000 rpms.. All stemming from talking to a racer. all they want is power in a high RPM package and that's all they are geared up to talk about. If this is the same guy who told you the chambers were out of alignment with the bores, I would most definitely question anything else he told ya. If he says this combo WORKS on a race car, he's out of his mind. they don't even breath above 5000 RPM and in a race car, he would be pushing it above 6,000... You're not building a race car, so.. race car people are prob not your best bet for info on what you're doing..

Your other good option is vortec heads.. that leaves you with buying a new intake. vortec ports are much taller than conventional chevy intake ports requiring the newer intake. plus their bolts are beyond different than older intakes. but their intake runners and chamber design are incredible.
Posted By: Ram4ever Re: Building high MPG Motor for a 93 Vhevy Van - September 24th 2009 7:32 am
Amen to that Swimmster! Racing and economy are at opposite ends of the spectrum.

Clear skies!
Posted By: swimmster Re: Building high MPG Motor for a 93 Vhevy Van - September 24th 2009 11:33 am
Here's a link to another discussion on the subject..

oh. and if it's valve sizes you're worried about, 1.94 is the same size valves in the vortec 350 heads.

http://camaroforums.com/forum/archive/index.php/t-8445.html

and another.. keep in mind, this is a specific application.. But if THIS thread doesn't back up what i'm tellin ya, then i'll stop wasting my time...

http://www.sallee-chevrolet.com/Discus/messages/653/2631.html
Posted By: burr_78g10 Re: Building high MPG Motor for a 93 Vhevy Van - February 07th 2010 8:31 pm
Something to consider in your build is long connecting rods, I'm running 6" rods in my 385 (stroker 350). You build a shorter stroke 350 with these rods I bet it'd help, from what I understand it reduces a lot of the sideloading as the piston moves in the bore.
Posted By: Patriot4Life Re: Building high MPG Motor for a 93 Vhevy Van - February 07th 2010 10:33 pm
i had a CNG kit for a tpi chevy 350 that i just sold would have been perfect for your project well mpg wise power wise not so much
Posted By: 2percent Re: Building high MPG Motor for a 93 Vhevy Van - March 17th 2010 3:53 pm
Step 1 to building a high MPG engine would be minimizing parasitic losses through the use of friction reducing coatings, these same coatings can be used inside the transmission to further reduce parasitic losses.
Step 2 would be blueprinting the engine to ensure proper clearance between all moving parts.
One key to maximizing torque is too maximize lift w/o increasing duration, 1.6 rockers will increase lift substantially while only slightly increasing duration.
Decking the block for zero quench is another trick to maximize static compression w/o changing the heads or pistons, i prefer a zero deck with a .040" compressed head gasket, ya gotta leave room for rod stretch unless ya want the pistons smacking the head.
Optimize the a/f ratio to all the cylinders, carb'd V-type engines such as the V8 suffer from lean mixtures in the corner cylinders, this is because they are the farthest cylinders from the carb and fuel falls out of suspension in the intake runners, because the cylinders are farther away more fuel falls out of suspension and these cylinders run lean, the intake manifold can be modified to correct these issues by increasing velocity in the runners leading to the corner cylinders, this is done by polishing the short side radius in the affected runners.
I don't know when to stop so i will stop here and wish you well.
Posted By: Danimal Re: Building high MPG Motor for a 93 Vhevy Van - July 21st 2010 4:18 pm
you're probably going to have a short lived tranny if you're running a 4l60/700r4 under 2000 rpm's at 70mph.
They require a certain amount of line pressure to keep from slipping at that speed, which they wont get below 2k.
Hi guys
I was reading this thread with big interest.
Last week my headgasket was blown and yesterday I got the bad news that one of my heads is totaly worn out.
But the upside of this is that I can do something else for a change. I have to spend money on another set of heads anyway.

I have a 350 Tbi (10054727) in my 1990 G20 and I like the idea of having some more power. I almost never drive faster then 90mph.
I probably can get a hold of a set of 305 heads an the 305 Tbi unit.

Now my question is what exactly i have to do to make this work? I've read everything that was written here, but as I am a bit unsure, I like to have a sort af step by step to make it a bit easier for me to understand.

I hope you guys can help me with this.
Posted By: maples01 Re: Building high MPG Motor for a 93 Vhevy Van - February 11th 2012 11:27 pm
A high MPG engine, that would be a 5.7 Oldsmobile diesel, in our 1980 Cutlass we would get 30 city 35 highway, those were heavy cars too. I'd love to have one to put in my van, I just don't have the cash, they were slow on take off, but racing doesn't provide the best mileage.
Posted By: Greywolf Re: Building high MPG Motor for a 93 Vhevy Van - August 16th 2012 6:42 pm
Hope this in the right place,need to replace my 93 GMC Vandura 5.7 TBI,wanted to go to a 4 bolt main motor,i'am looking for a place to get it, i'd like to keep it stock so as i can use the parts already on my motor,just need to know if anybody can recomend a good place to look for one i want a new motor not rebuilt,Thanks for your help,joe. cheers
Posted By: HighwayStar Re: Building high MPG Motor for a 93 Vhevy Van - August 16th 2012 10:54 pm
Joe, check out Summit Racing they have some good deals on SBC engines . I think you can get a new crate motor for around 1200 bucks when there on sale..
Posted By: Greywolf Re: Building high MPG Motor for a 93 Vhevy Van - August 17th 2012 1:21 am
cheers Thanks Pete
Posted By: gman Re: Building high MPG Motor for a 93 Vhevy Van - February 15th 2013 8:33 pm
305 heads are VERY restrictive with 58cc chambers, when these heads are bolted on a 4.000" bore the valves becomes extremely shrouded, don't do it. Much better with heads designed for a 4.000" bore instead of 3.875" bore on 305 heads.
Rhoad's lifters are designed to allow the use of large cams with lots of duration to run on the street without losing usable vacuum, they would server you no purpose at all and may do more harm then good by bleeding down at lower rpm's and increasing valve lash.
The key to making low end torque can be 1 word "VELOCITY", you want the air flowing through the engine at low rpm's to be moving very fast, this increased velocity is what helps builds torque, running a small diameter exhaust system to keep the gases hot and flowing fast, hot gases flow faster then cold gases.
you can run 6.0" rods but you either have to raise the piston pin a 1/4" or shorten the stroke on the crank to accommodate the increased rod length.
Good advice on wrapping the headers to keep the gases hot entering the collector but wrapping the exhaust will also help it to retain moisture and rust out a little quicker.
Deck the block for zero quench, quench is the distance from the top of the piston at TDC to the flat section of the cylinder head, this brings the piston out flush with the block and closer to the head reducing the quench area, combustion is supposed to take place inside the combustion chamber, when you have excess quench combustion is allowed to take place in other places then the chamber and this is not good, instead of packing that condensed A/F mixture into the chamber it is allowed to expand inside the cylinder and invade the quench area, this greatly reduces engine power by weakening the mixture that was burned in the chamber, propagation is the travel of the flame front across the face of the piston, since gasoline does not explode inside the engine but instead burns very rapidly and we want to mold that rapid burning fire into a wheel that rolls across the top of the piston and pushing it down.
Do not offset the piston pins to straighten the rods, there is good reason the factory offsets the pin, offsetting the pin reduces piston slap and corrects bore alignment with the crank center-line, the engine bore is not centered over the crankshaft, it is slightly offset towards the exhaust side, the pin offset is used to correct the bore/center-line alignment with the crank.
Increasing torque without affecting the power-band can be as simple as high-ratio rockers, just keep in mind that when you change the ratio to lift the valve higher you also change where the rocker contacts the valve stem and you can rapidly wear out a set of valve guides if you don't pay attention..
I'll read through all these replies eventually and indulge you some more..
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