jerrybramlett

There is an article on this subject in the latest issue of the NCRS Restorer. There's also a recent thread about it on the NCRS Discussion Board. In my opinion, they both overstate the potential FI problems caused by the 10% ethanol content in almost all modern pump gasoline.

Here's the short version of my opinion: you needn't worry about your non-Viton Rochester FI seals leaking because your gasoline contains 10% ethanol.

I'm not going to post in the discussion on the NCRS Board for many reasons, but this is what I would say. If my opinion might give you some peace of mind, please keep reading. However, you certainly don't have to take my word for any of this. Just sit at your computer and Google the crap out of "ethanol auto seal damage", "ethanol corrosion", "Nitrile swelling", "alcohol swelling in elastomers", etc. You'll find a wealth of information from sources with more credibility than me.

There's some ethanol in just about all of the pump grade gas you buy today. Retailers do not have to post signs warning the consumer if the ethanol content is no more than 10%, and most stations don't. You can buy "Low Lead" Aviation gasoline with a 100 octane rating at most airports, and it has no ethanol in it. (However, it has a boil-off temperature range no better than pump gasoline for cars, so it does not help prevent percolation.) You can buy racing gasoline in most large cities. It is formulated similar to pump gasoline, but with no ethanol and a much higher boil-off temp range. It also contains stabilizers to give it a longer shelf life. (Most brands offer several different octane ratings in the 108 to 120 range. All of the octane levels of racing gasoline provide very good protection from percolation.)

Racing fuel is not gasoline at all. It is alcohol, but not ethanol ("grain alcohol"). It is methanol, or "wood alcohol". Usually it is run straight, but some racing rules do allow additives such as nitromethane. I've never heard of anyone running methanol mixed with gasoline on the street in the last few decades, but I believe it was done for a while shortly after WWII. It is extremely corrosive. Methanol suppliers warn racers to drain their fuel systems every day after methanol use and then flush the system (and engine) with gasoline.

Ethanol does cause most Buna-N and Nitrile synthetic elastomers to swell as they absorb the alcohol. The growth is quite dramatic; I've seen as much as 30%. However, it does not appear to cause a seal to degrade. In other words, the seal is just as strong, but it is slightly softer and much larger from the swelling. If you allow the seal to dry out, it will go back to its original size and hardness.

Viton is the proprietary name for a Dupont synthetic elastomer that is ethanol resistant. There are other companies with similar spec products, but they can't call them Viton because that name is copyrighted. Viton-spec elastomer products generally cost about eight times more than those made of Nitrile or Buna-N for this reason!

There is only one manufacturer / supplier of complete FI rebuild kits that I know. Until a year ago, this manufacturer used only Nitrile for the tubing o-rings, pump shaft seals, spill valve o-rings, and axle link grommets in his kits. These products would swell quickly if dropped into pump gasoline sitting in a jar. However, they are actually installed in positions where they are captured (constrained) in the FI unit. In other words, they can not move and have nowhere to expand, so these seals do not leak while installed from exposure to pump gasoline with 10% ethanol.

This one manufacturer now sells kits with these few seals (only) made of something like Viton. He makes them out of a brown colored elastomer so he can easily tell them apart from his existing stock of black Nitrile elastomer seals. Any FI unit rebuilt with an aftermarket kit during the last 8 months probably has these few seals made of this brown ethanol resistant elastomer. Any units rebuilt with older aftermarket kits probably have all Nitrile (or Buna-N) seals in them. The units sealed with Nitrile and Buna-N are in no significant danger of developing leaks solely because of the 10% ethanol in modern pump gasoline. All of those seals are in constrained applications.

If any of you still have questions about what I've said here, please call me. I'm now completely typed out on this subject.

wmf62

Jerry
i agree with your observations. in the years that i ran ethanol-laced gasoline, i saw no leakage from any area that used the old style o-rings.

percolation finally did me in....
Bill

MikeM

Jerry:

We've had 10% ethanol in the gas here for many years. At least twenty, maybe twenty-five. I haven't had any leakage problems in that time.

PAmotorman

as some one who has rebuilt a few carbs i have seen the black rubber accelerator pump cups become very hard when used with gasoline with ethanol. the newer carb rebuild kits now come with a blue or green colored pump cup which i assume are a different material.

78Vette-SA

Jerry,

Not quite related but a curious question about seals. A couple years ago the seals went in my 63 Fuelie. They were literally like little squishy worms when I pulled them out. The smell from the gas tank was putrid and I will never forget it.

The only thing I can contribute it to (besides stupidity but lets not go there) is I put some STP Octane Booster in the tank and shortly there after a good dose of Stabil as I was still in the middle of restoring the car and had the motor test fired up in the chassis only as a run stand. I never drained the tank and let it sit for about a year with this cocktail in it.

Ever heard of anything like it?

Thanks,

Joe..

jerrybramlett

No.

All of the seal failures I've encountered were due to improper installation, age hardening/cracking, and physical wear. I've never seen one that degraded through chemical reaction, but it's certainly possible others may have.

PAmotorman

i don't do FI but i have seen holley carbs where they have had "octane booster" in them and it has eaten the dichromate plating off of the inside of the float bowls and the accelerator pump diaphragms were rock hard.

70vert

I've been quite worried ever since I read the article in Restorer; to bad the Restorer article didn't have an opposing point of view. What you say, Jerry, makes good sense; thank you for your posting. I will keep my hands off my unit for now and will use due diligence by inspecting my unit more closely after each run for any evidence of a leak.

John