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#325806 - September 13th 2009 1:35 pm Re: Building high MPG Motor for a 93 Vhevy Van ***** [Re: racprops]
swimmster Offline
old hand

Registered: February 16th 2008 9:41 am
Posts: 1189
Loc: New York
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..
_________________________
Yeah..... I know I know.... It's NOT a van... But if you squint, It could be a REALLY long van?


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#325885 - September 13th 2009 10:30 pm Re: Building high MPG Motor for a 93 Vhevy Van [Re: swimmster]
racprops Offline
newbie

Registered: September 08th 2009 10:18 pm
Posts: 33
Loc: Phoenix AZ
OK Have you done the 305 TBI trick adn have you done the 305 heads on a 350??

Rich

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#325896 - September 13th 2009 11:00 pm Re: Building high MPG Motor for a 93 Vhevy Van [Re: racprops]
swimmster Offline
old hand

Registered: February 16th 2008 9:41 am
Posts: 1189
Loc: New York
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.
_________________________
Yeah..... I know I know.... It's NOT a van... But if you squint, It could be a REALLY long van?


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#325961 - September 14th 2009 11:17 am Re: Building high MPG Motor for a 93 Vhevy Van [Re: racprops]
swimmster Offline
old hand

Registered: February 16th 2008 9:41 am
Posts: 1189
Loc: New York
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.
_________________________
Yeah..... I know I know.... It's NOT a van... But if you squint, It could be a REALLY long van?


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#326022 - September 14th 2009 2:37 pm Re: Building high MPG Motor for a 93 Vhevy Van [Re: swimmster]
racprops Offline
newbie

Registered: September 08th 2009 10:18 pm
Posts: 33
Loc: Phoenix AZ
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.


Edited by racprops (September 14th 2009 5:23 pm)

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#326044 - September 14th 2009 3:56 pm Re: Building high MPG Motor for a 93 Vhevy Van [Re: racprops]
swimmster Offline
old hand

Registered: February 16th 2008 9:41 am
Posts: 1189
Loc: New York
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.
_________________________
Yeah..... I know I know.... It's NOT a van... But if you squint, It could be a REALLY long van?


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#326122 - September 14th 2009 11:02 pm Re: Building high MPG Motor for a 93 Vhevy Van [Re: swimmster]
racprops Offline
newbie

Registered: September 08th 2009 10:18 pm
Posts: 33
Loc: Phoenix AZ
Please show my the front of your engine so I can see if I can use my stock belt set up..

Rich

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#326159 - September 15th 2009 7:19 am Re: Building high MPG Motor for a 93 Vhevy Van [Re: racprops]
swimmster Offline
old hand

Registered: February 16th 2008 9:41 am
Posts: 1189
Loc: New York
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.



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.


Edited by swimmster (September 15th 2009 7:27 am)
_________________________
Yeah..... I know I know.... It's NOT a van... But if you squint, It could be a REALLY long van?


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#326225 - September 15th 2009 10:34 am Re: Building high MPG Motor for a 93 Vhevy Van [Re: swimmster]
racprops Offline
newbie

Registered: September 08th 2009 10:18 pm
Posts: 33
Loc: Phoenix AZ
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

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#326230 - September 15th 2009 10:40 am Re: Building high MPG Motor for a 93 Vhevy Van [Re: racprops]
racprops Offline
newbie

Registered: September 08th 2009 10:18 pm
Posts: 33
Loc: Phoenix AZ
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

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