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Re: Building high MPG Motor for a 93 Vhevy Van
Doc 2% of Canada, EH!!!! #326429 September 15th 2009 7:26 pm
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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

Re: Building high MPG Motor for a 93 Vhevy Van
racprops #326467 September 15th 2009 9:05 pm
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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..


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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Re: Building high MPG Motor for a 93 Vhevy Van
swimmster #326469 September 15th 2009 9:06 pm
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Also.. any truck front accessory mounts will work in the van..


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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Re: Building high MPG Motor for a 93 Vhevy Van
swimmster #326491 September 15th 2009 10:35 pm
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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



Re: Building high MPG Motor for a 93 Vhevy Van
racprops #326840 September 16th 2009 11:03 pm
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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


Re: Building high MPG Motor for a 93 Vhevy Van
racprops #326841 September 16th 2009 11:05 pm
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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


Last edited by racprops; September 16th 2009 11:06 pm.
Re: Building high MPG Motor for a 93 Vhevy Van
racprops #326972 September 17th 2009 2:12 pm
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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

Re: Building high MPG Motor for a 93 Vhevy Van
racprops #327049 September 17th 2009 8:44 pm
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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.


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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Re: Building high MPG Motor for a 93 Vhevy Van
swimmster #327094 September 17th 2009 10:52 pm
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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


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