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Amphilophus · 03-23-2005, 01:06 AM

Is it possible to build a engine that can put down 450-500 horsepower N/A and get 14 or 15 mpg? how would it be done? I plan on putting overdrive tranny in but what could be done to the engine to make it more efficent? any help would be great.

Amphilophus · 03-23-2005, 01:06 AM

Is it possible to build a engine that can put down 450-500 horsepower N/A and get 14 or 15 mpg? how would it be done? I plan on putting overdrive tranny in but what could be done to the engine to make it more efficent? any help would be great.

Rholmes · 03-23-2005, 01:43 AM

455,stock 87 cc e-heads,comp xe288/296hr cam,1-3/4 super-comp/or Doug headers,3" exhaust,Tremec 5 speed/355 rear.Recurved HEI or drop in MSD,Box stock 850dp,or Quad prep by Cliff or Jon.There ya go

customizedcreations · 03-23-2005, 05:51 AM

Better question would be what do you want to do with the car ? If your looking mainly for mileage and performance on a daily driven street car, then nitrous would probably be a great choice. If you want to stay NA it will cost more money and be more likely to be unreliable. The combo above may get you close to what you want hp wise, but the 850 dp is definitely not going to get you anywhere near 14-15 mpg. The qjet would work better for that but I would still have to say that you wont be close to your 14-15 mpg target.

If you want a nice 11 second street machine, it would be easier to do that then shoot for a specific hp #.

Good luck

Engo · 03-23-2005, 06:30 AM

Yes that would be possible. EFI would be the hot ticket to get decent mpg out of it.

LouisianaGuy · 03-23-2005, 08:01 AM

Qjet by cliff will get you close

maby.
Mike

455guy · 03-23-2005, 08:04 PM

Go with a high torque 455, 3.23's or less and an over drive auto(more gear) or 5 speed or 6 speed stick and 14 to 15 should be fairly easy. Look at the max torque specialties web site. They run 500/472 cads, 2.73's and do very well on 1/4 mile and gas mileage.. Every one assumes if you have a high perf motor, bad gas mileage is just a nessicary evil but with some thought and the right parts, it doesn't have to be that way. I ran a mild 455, stock converter with 3.42's in a heavy 74 ta and got 15 ish and ran 13.34's in the qtr on my first build..

wheelspin · 03-23-2005, 09:08 PM

Amp,

Welcome to the Forums.

See my post on a "question of torque" inquiry in this topic. Planning on attending Pontiac Heaven @ Speedworld in April? It's a good oportunity to see some fine and fast Pontiacs and meet some of the folks that hang out here.

Les

Amphilophus · 03-23-2005, 10:50 PM

thanks for all the replies. my main goal is to build a 11-12 second street car that can get decent gas mileage so i can drive it often. I dont really car too much about cost because I want to do it right and have a car I can drive for a long time. I would also like to keep the 400 in it. any suggestions for a 400?

I do plan on going to the event in april I just wish my firebird would be ready to drive to it. thanks again.

olblue · 03-24-2005, 12:51 AM

O/D EFI.

Cliff R · 03-24-2005, 04:38 AM

The 455 in the Ventura made 494hp on KRE's dyno, runs well into the 11's and gets 13-15mpg's. We seldom check the milage as it is difficult to consume a full tank of fuel without a few full throttle blasts! Even so, we easily get 200 miles out of 14 gallons and on occassion have went 220 miles. The race weight for the vehicle is 3760 lbs and we use 3.42 gears with a 27" tall tire, no overdrive......Cliff

Cliff R · 03-24-2005, 04:42 AM

PS: We use a 1977 Pontiac q-jet and 1975 Pontiac HEI distributor. The q-jet is custom calibrated exactly for the application and the distributor uses stock springs, weights, center cam with stock internals other than the recent addition of Mallory's new module with adjustable rev limiter. We use 89-90 octane fuel, static compression ratio on the engine is 10.48 to 1......Cliff

olblue · 03-24-2005, 07:53 PM

I'll bet you could get 18 to 20 MPG with an O/D
and that differential.

3.42's...Those are "Cadillac or Suburban" ratio.

1968_Injunhed · 03-26-2005, 08:51 AM

I went from 6-8 MPG with a 850 DP to 12-14 with a Q-jet just like Cliff runs...since he built it...much better at 2.25 per gallon. Oh, and it runs better too!

uneasyrider · 03-26-2005, 07:03 PM

Yes, and here is one that gets 15mpg with a 4-speed, 3.80 gears, and 414rwhp. It's not a Poncho but it's an example.

It isn't pretty but it works.

uneasyrider · 03-26-2005, 07:05 PM

And a picture of the not so pretty engine.

larry davis · 03-26-2005, 10:33 PM

Those two are not akin!

olblue · 03-26-2005, 10:44 PM

If you didn't have a Pontiac, you would probably be tickled pink to have a Mopar like that.

I would...

Cliff R · 03-27-2005, 06:29 AM

I owned, drove and raced a 1970 Roadrunner for many years. 440 powered, 727, turbo action converter, 4.56 gears. With the addition of a Mopar Purple Shaft cam, Torker intake and 850 DP carb it was a strong 12.30-12.50 car with open exhaust/race slicks.

My Ventura (daily driver) uses an iron intake, q-jet, 3.42's and DOT's and runs 11.70's at 115mph....and is 270lbs heavier!

I'm sure I could have "tweaked" the Mopar into the 11's but not in nearly a mild state of tune as the Ventura.......Cliff

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