I am currently building an 64 olds 394 with original 10.25:1 Compression. While being on this forum for a few months I have read horror story's about using octane ratings that are too low for the High compression 1 Generation rocket motors. My plan was to use 93 octane with a booster but until recently I didn't know E-85 had such a very good octane ratings, currently of around 106. Which is very close to the factory premium 101 octane that they were designed to run on. My question is could the 394 run on E85 or what modifications need to be done to run it? it seems like a good cure to this problem. E-85 is very common in my area and I would have no problem getting it.

 

Can I run E85?

The Basics of Switching to Ethanol

You've seen cars making huge power on E85. However, you can’t just switch fuel. That would make your car run worse. It could also cause damage.

How does it make more power?

E85 contains less energy per gallon than gasoline. But, an engine designed for E85 can make more power. This requires more fuel.

More fuel volume and the chemical makeup of E85 keep the Air/Fuel Mix cooler. E85 also has a higher Octane Rating than gasoline. This allows increased:

• Ignition Timing Advance
• Compression
• Boost

How can it damage parts?

E85 has a different chemical makeup. It can damage rubber parts.

Hot spots in the combustion chamber can cause Pre-Ignition.

Fuel System Requirements

The fuel system must be designed to deliver more fuel. Every part of the system needs to be alcohol compatible. Some parts to consider are the following:

• Fuel lines and hoses, especially inside the tank.
• O-rings and seals in the injectors, filters, couplings, and sending unit.
• Fuel Pressure Regulator.
• Fuel Filters, Stainless mesh filters are best.
• The Fuel Injectors and The Fuel Pump need to be compatible with E85 and sized to deliver more fuel.
• You may need a cooler spark plug to reduce the risk of pre-ignition.

E85-Ready Carburetors are available. Some are coated to prevent corrosion. They have updated floats and larger jets. The internal passages are also enlarged to handle more fuel. E85 Conversion Kits are also available for some carbs.

E85-Ready Fuel injection Kits are also available. The ECU’s are programmed to work with E85. They have the right seals and O-rings. More good news—they also work with gasoline. If you upgrade to fuel injection and you might ever run E85, just buy a compatible kit from the start.

Here is a start of things to consider, courtesy of Summit Racing..

​​​​​​​Thirdcoast

 

You cannot run a conventional gasoline engine on E-85 no matter how appropriate the octane. When you're ready to run the engine, put in the 93 octane and see how the car does. If it runs fine, try a lower octane. If it runs ok with that, try a still lower octane. When it starts to knock, go back up one octane level. There is no advantage to running a higher octane than necessary. Doing so doesn't clean the engine or make it run better or give you better mileage or make the engine last longer. It's just a waste of money.

Don't overthink this. These cars from back then were not magical beasts that required special formulations of gasoline that is not available today or that now require special additives.

I had a '67 Delta 88 with a high compression engine for about decade before selling it early last year. I just put in the highest octane fuel available at the corner gas station. I never had a problem.

 

As Jaunty stated most of us can run our engines on 91 to 93 octane with higher compressions.

Just because E85 is available in your local driving area does not mean it's available everywhere you roam. Once you convert you can only run E85. Cliff Ruggles can rebuild your carb or get you a kit to do it yourself. You also need to change all rubber lines on your car to be compatible. Also be aware that E85 can be anywhere from 51-85% and can vary greatly depending on time of the year.
Quick Tech: The Ethanol-Friendly Q-Jet Rebuild How-To! (hotrod.com)

 

X2 don't over think this ( I do the same thing at times) My stock 36K mile 63, 394 A/C Starfire runs fine on 93 with initial timing set at factory spec. 7.5 degrees. No issues...,

 

This is not true. E-85 engines can run on conventional gasoline. That's why they're called "Flex-Fuel" vehicles. It's the opposite that's not true.

If E-85 vehicles were limited to only E-85 gas, no one would buy them because, as you say, you don't want to go somewhere where there isn't any available and then discover you need a fill-up to get home.


https://www.thirdcoastautos.com/blog...-fuel-vehicle/

 

We were talking old cars Jaunty keep up. So let me rephrase my comment for you, there are no flex fuel carbureted engines. Carbureted non-computer controlled engines cannot run on both, it's either one or the other. A carb setup for E10 will run extremely lean on E85 and a carb setup for E85 will run extremely rich on E10.

 

The biggest problem with changing to E85 is that you need a completely different carb. The stoichiometric AFR for E85 is about 9.75:1 vs 14.7:1 for gasoline. The fuel passages in the carb need to be about 50% larger. You can buy carbs designed for E85, and you can even swap back and forth with a gasoline-calibrated carb, but without changes to the engine, you're likely to be down on power. Timing needs to change, and CR really wants to be higher to optimize for E85. Fuel system materials compatibility is also a problem. You'll need to replace all the non-metallic parts in the fuel system, including the sending unit. It can be done, but it really isn't worth it. Also, since this won't be a "flex fuel" conversion, you can only drive the car in areas that have E85 available.

 

Everyone needs to remember the following fact - there is such a thing as inaudible detonation.

 

Everyone also needs to remember that the price of tea in China is currently 49 cents per pound.

What I'm having a hard time figuring out, though, is what either of these has to do with the current discussion.

 

Koda was responding to this:

The fact that it "runs fine" (for now) does not mean that you aren't experiencing detonation.

 

So how do you know detonation is going on if you can't hear it?

 

Here is a refresher. The 394 used a Rochester 2GC or 4GC carb. 394's never had a Quadrajet or a manifold for a Quadrajet.
I believe I would just run the currently available 93 octane gas, preferably the non-ethanol stuff.
.....Just my two cents worth.

 

Just one of those challenges that makes old car ownership so much fun!!

 

When you see holes in pistons , broken rings , etc .