how do i convert my 75" pontiac 400 to run e85, and be fuel injected?

Asked by Jul 04, 2016 at 07:59 AM about the 1975 Pontiac Firebird Formula

Question type: Car Customization

6x heads
edelbrock airgap intake
.600 lift cam
forged 455 crank
forged flat top pistons
forged conecting rods
hydraulic roller rocker
6x heads have been ported and polished.

10 Answers


With your engine mods E85 won't cut it, that is a low output fuel and you have a high output engine, if your wanting to stay with pump gas then get a Holley fuel injection unit and run high test with a bottle of 104 added at every fill up. If you really want to be emissions friendly then convert it to Propane or CNG.

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Purchase one of those Edelbrock or other manufactures .. MSD Fuel Injection systems for your engine. After its installed have the car properly tuned on a Dynamometer for the Corn Alcohol, E85 fuel... gasoline with alcohol mix.

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To my understanding e85 fuel is 110 octane, so why do you think it is insufficent for my engine? what would you run and why? My thoughts on e85 were its a whole dollar fifty cheaper than premium gasoline(93octane) and would allow my engine to run alot better. that was why i wanted to convert. i currently run 93 octane it runs but it would be alot happier with higher octane. what about running alcohol? im looking for a cost effective alternative.


With a .600 lift on your cam why would you even consider a low grade fuel? If you were planning to run E85 fuel in the first place, why did you not build an engine to do so? Unless you purchased this vehicle like this. Sounds like you have some hp. going on. Holley makes a niece 4 barrel fuel injection system with a stand alone computer for tuning for about $2000

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I bought the car already built. The stand alone computer can tune to whatever fuel you run? similar to the flex fuel vehicles?


Well sure, but the concern here is the horse power you have going on. Port & polished, .600 lift on the cam, flat top pistons, close to 10:1 compression, this configuration in itself does not like a low grade fuel for combustion, not to mention all the deposits the fuel leaves behind that a higher hp. engine does not like.

1 people found this helpful.

so what type of fuel would you run?


Premium, it is so much more cleaner burning. You can only use E85 in vehicles that are certified to use it. Do not use E85 in a car that is not certified for it. Expensive damage will result! Flex-fuel vehicles will get significantly lower fuel economy when running on E85 (typically 20-25% lower) compared to running on gasoline. All tho the octane rating is 110, the fuel is made up of 85% corn-based ethanol and 15% gasoline. The fuel is not as clean burning. .....Back in the day more horse power meant good gas mileage. I suggest just having the motor perform as it is designed, running the best it can and using premium gasoline. In the long run it will benefit you in cost.


You can run E85 if tuned for it just plan on burning a LOT more of this than conventional gasoline. I've tested it (Dyno) in several engines.. NOT my choice but..Purchase and burn what ever you want some guys like Diesel in the C12 to C15 range / kerosene fuel! LOOK up BTU's in fuels, and Carbon chains most people are clueless. Optimized to run ethanol (alcohol) -specific software? That ethanol will burn cleaner, last longer, and make more power. Research this, OR NOT lots of info..


Premium, or go and change to Propane. A good Propane engine has 11:1 compression ratio and your at 10:1 so your well within a good alternative fuel engine and Propane is easier to get than alcohol.

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