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Building high MPG Motor for a 93 Vhevy Van
#325282 September 10th 2009 12:23 pm
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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




Re: Building high MPG Motor for a 93 Vhevy Van
racprops #325288 September 10th 2009 12:34 pm
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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.


Ken Schwarz
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Re: Building high MPG Motor for a 93 Vhevy Van
Superbeast #325293 September 10th 2009 12:49 pm
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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?


I go to Truck-ins. How about you?
Re: Building high MPG Motor for a 93 Vhevy Van
matchstickBGV #325305 September 10th 2009 1:56 pm
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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.

Last edited by CatFish; September 10th 2009 2:02 pm. Reason: TPI not TBI - duh
Re: Building high MPG Motor for a 93 Vhevy Van
CatFish #325433 September 11th 2009 9:35 am
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“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

Re: Building high MPG Motor for a 93 Vhevy Van
racprops #325470 September 11th 2009 2:00 pm
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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?


Re: Building high MPG Motor for a 93 Vhevy Van
CatFish #325504 September 11th 2009 4:59 pm
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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.


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 #325509 September 11th 2009 5:20 pm
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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?


Josh Souders
Performance Inc

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The voices in my head may not be real, but they have some good ideas!
Re: Building high MPG Motor for a 93 Vhevy Van
josh_performanceinc #325554 September 11th 2009 10:18 pm
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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.


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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