87 octane 390

[fryedaddy]

can a bone stock 66 model 390 live happy on 87 octane fuel?

[fryedaddy]

the reason im asking is i had some cheap winter grade fuel boil in my carb this spring,so i added some race gas and it never boiled again.i had a guy on another forum argue that he tunes his 66 390 to run on 87.i told him 87 boils in my carb.he all but called me a liar

[machoneman]

Sure but....it needs to be in tune. That and a few other things to consider. If it's all OEM, it likely has that crappy nylon-toothed cam gear that will eventually start, via a loose chain, retarding your cam's timing and break when you least expect it. A new iron or steel cam gear in a timing chain set will put things back in order. You might also consider new valve seals (and maybe a fresh valve job) to keep oil off those piston tops. 

Btw, is that gas 10% ethanol laced? if so, the ethanol is the issue. Try some 100% non-ethanol gas (hard to find) not race gas and see if it improves.

[fryedaddy]

ethanol is the problem.that guy says he uses any 87 for 20 years with no problems.i even had 93 boil in mine i would never use 87 in my fe no matter what  would it be hard on it to turn big rpms with 87

[57 lima bean]

Nonoxy fuel would work for you.87 octane is not carb friendly.I had trouble with it in my 8.5 to 1 460.

[fryedaddy]

im glad to find someone to agree with me on this,he said he even runs 87 in his tri-powered 406,and he said it runs just as good

[jayb]

I've had the same problem with fuel boiling in the carb; one reason I now prefer EFI.  Anything with ethanol is going to have a much lower boiling point than the fuel available back when the cars were new.  The best way to resolve the problem if you are going to run a carb is to go to a return-style fuel system.  Two fuel lines, one from the tank and one back to the tank, and a return style fuel pressure regulator, from Moroso or Aeromotive.  Fuel not needed by the carb is bypassed and sent back to the tank, so it can't sit in the fuel line in the engine compartment and get hot.  The system will be a pain to install but it will allow you to run fuel with ethanol.  Or just buy the non-oxygenated fuel as Steve suggested.

[Royce]

He could run 87 in a 75 390 truck engine, but a 60's 390 with 10 to 1,  no way.  Unless he backs the timing down to about 28 degrees and runs 140 degree water through it.. "runs just as good" could mean anything depending on the individual. I had a factory 406 G code. You had to back the timing way down and drive it easy or it would ping like crazy even with 93 unleaded.

[fryedaddy]

thanks.im the first to admit it if im proven wrong,but some people you are wasting your time trying to convince them otherwise

[Lenz]

I've seen what ethanol will do to a carb first hand.  When you couple that with the boiling issue you have the reason why I will not use any grade of fuel that contains ethanol in my Galaxie.  Settled out on corn free Shell 91 at the start of this year, zero issues.