65 fuel choice

greetings, Rivs what are your recommendations for the proper fuel for my recently rebuilt 65 401. The rebuilder, who claims to be a nailhead expert, says to use regular low octane gas and indeed the car runs great on that. But someone else told me I should be running on ethanol-free (marine grade)gas, which just became available locally. It's 5./gal. but I don't put many miles on this car. Any ideas? Thanks Drew

greetings, Rivs what are your recommendations for the proper fuel for my recently rebuilt 65 401. The rebuilder, who claims to be a nailhead expert, says to use regular low octane gas and indeed the car runs great on that. But someone else told me I should be running on ethanol-free (marine grade)gas, which just became available locally. It's 5./gal. but I don't put many miles on this car. Any ideas? Thanks Drew

If you can buy alcohol free fuel in your location by all means use it. The alcohol is hard on carburetors, fuel pumps and gas tanks. Where I live I have to drive 90 miles one way to purchase non alcohol fuel so it isn't really feasible for me to buy it. It is amazing how

the nailhead Buicks will run on pump gas even with high compression, where a Chevy or Pontiac or Olds v-8 will ping like hell on the same fuel. My GTO has to use racing gas to stop the detonation.

http://pure-gas.org/

Buy the highest octane rating that they sell.

Ed

I use 93 octane as it is very close to the original octane used back in the day (the average of Motor and Research octane ratings specified in owners manual). This formula is how today's octane ratings are calculated: (M + R)/2.

Drew,

It depends on how your engine was rebuilt. Did the rebuilder lower the compression down to 9 to 1? Or is it still at stock specs? If it was rebuilt to 9 to 1 or therabouts, it probably will run fine on 87. If it is still at its high compression specs, then 93. As others recommended, if you can get ethanol free gas definitely use it.

When the engine was rebuilt, did you rebuild the carburetor? If not, it's time to do that as well using alcohol (ethanol) resistant gaskets, And as long as you're getting your hands dirty, it's time to replace all of the flexible fuel lines with the same - just ask for fuel injection hose.

Hey guys! Thanks for all the response. To tell the truth compression ratio wasn't properly discussed. I was so excited to get the engine back and in the car I probably assumed it would be back to specs, but since he recommended regular gas I guess it could have ended up lower than specs. HMMMM. Maybe time for a compression check, if just for curiosities sake. After all, the engine has performed flawlessly for 1000mi. Ed, I replaced the carb with an original type Carter rebuild from Canada of all places. I don't know if it was rebuilt with resistant rubber & gaskets. If not, hopefully I haven't done serious damage to it yet. For now it works like a charm. We'll see. I haven't filled up with ethanol-free yet but will be sure to report the results. As much info as you guys can throw at me is greatly appreciated. Drew

In an article in The Riview, Vol. 24 No. 4, July / August 2007, titled 'Advice from an Automotive Engineer', p. 8, by Denny Manner #287, retired assistant chief engineer & designer for Buick / GM powertrains, Denny wrote:

"Use Adequate Octane fuel to avoid detonation. Beginning in 1971, all engines were designed for lower octane fuel, and will operate fine on today's unleaded blends. Pre-1971 were designed for 94 - 98 octane leaded fuel. Unleaded fuel has many benefits. It reduces hard carbon deposits in the combustion chambers, eliminates gray residue in the oil pan, provides significantly longer sparkplug life, eliminates deposit buildup on the valve seats, causing burnt valves and overall longer engine life.

"The only concern with using today's unleaded fuels in our pre-'71 engines is adequate octane to avoid spark knock or pre-ignition. This can cause damage to the pistons and head gaskets in high-compression engines of the '50's through 1970 models. Spark knock usually occurs under heavy or full throttle power. Many engines will operate satisfactorily on 94 or lower octane. Evaluate different brands for best results. If persistent knocking continues, try retarding the spark timing four to six degrees.

"Make sure your distributor's mechanical and vacuum advance mechanisms are working properly. If necessary and when available, I add a few gallons of 110 octane racing fuel to each tank. Only as a last resort would I use an octane booster. If you are going to race the car, use high-octane racing fuel. I have also heard that cooler heat range spark plugs have helped to reduce spark knock."

See the rest of article for additional advice by Mr. Manner.