E85 jet and rod combo?

[elementaltoad]

I'd like to be able to run E85 with a spare Quadrajet I have for my 1969 Firebird. I have E85 readily available, with the higher octane rating, and having a spare carb, it would be nice to be able to utilize it. I know that the stock style fuel pumps may struggle to keep up and I will be running a nitrile diaphragm pump that should support 110gph+.

The engine is a basic bolt on Pontiac 350:
Edelbrock Performer intake
#17 small valve heads
7029268 Carburetor
Long tube headers
HEI ignition

The current 7029268 carburetor on the car uses a 72 jet, 42B rod, and a DA secondary rod. It has been running just about as well as I think I can get a stock 350 to run, MPG has been decent and it will fry tires through shifting into 3rd gear.

The spare 7029268 Carburetor I have hasn't been modified and has a stock 71 jet and 44B rod combo. The secondary rods are BE.

I know that E85 requires roughly 25-30% more volume, but what does that translate to as far as what rod and jet combo I would be looking at? Is there a method or formula to be mindful of when calculating that? Are there any other things to be mindful of when setting these up for E85?

[Cliff Ruggles]

There is a learning curve switching to E-85. 

I sell parts that hold up fine in it and high flow N/S assemblies to help keep the carb full and HP accl pumps to delivery more fuel when needed.

As far as tuning I can get you close put it often involves more than just jet and metering rods changes. 

Instead of just going bigger and bigger with jets and smaller with metering rods we often have the user install smaller air bleeds to reduce emulsion air and put more "signal" to the jets to bring in more fuel instead.

There is also a "learning curve" with E-85.  It hates cold engine parts and lower compression so works best when the engine is fully heat soaked and higher compression engines are better at effectively burning it.

Anyhow, I can help with parts to get you close right off the bench and parts that hold up fine using it........

[Mudsport96]

Cliff is absolutely correct about engine temp and e85.
Used to run a blow through carb setup on e85, and let me tell you this... if that engine was not at 220 minimum, it had horrible manners. It ran at 165-180 on c-16 fine. Then it was decided to try e85 for a cost savings experiment. Fought that thing to get it to part throttle and transition as the boost came on and it just fought back every step. Finally figured it out after about 2 months when i got pissed at the track and decided it was just going to over heat it and kill it. So after the 3rd hot lap it was around 230 in the staging lanes. And the idle was great and the part throttle to pull up was awesome, it even came up on the brake faster... ran its best et at 8.54. So switched the stat out for a hotter one and never had a problem again.
Well till the boost reference line came off and it nuked everything around the 900ft mark... but it still coasted to a 8.60 lol.
So yeah e85 is ok, but unless you have more than 10:1 or forced induction i wouldnt worry about using it in a carbed application.

[elementaltoad]

Thanks y'all! Sounds like it might be a better idea to build one off to the side in anticipation of a cam and heads combo later on. I went ahead and ran a tank of E85 to tinker with, and it runs surprisingly well, it had a bit of a lean pop at cruise but that was it, which I think I could adjust for with a power piston spring change.

I did notice that it wanted to sit and warm up before driving anywhere, it didn't like moving until you start getting some heat into the engine. That's with a Pontiac 350 that has around ~9:1 compression.

Cliff, the parts I am running in the carb now are from you, that 72/42B combo seems pretty spot on for a bolt on Pontiac. I honestly don't know that I could squeeze any more power out of it, just needs some fine tuning on the air door now. As always, your input and knowledge are much appreciated!