What octane fuel?

[Ben Herman]

Based on a little napkin math I've run a little over 10,000 gallons of 87 ethanol gas through my 383 since I bought it in 2013. I have revved it till valves float plenty of times. I've climbed the Rockies with it twice on 85? (whatever low grade is in Denver). If it's done any pinging it clearly never hurt anything. If you've rebuilt your carb while I've been alive with a new kit it'll do fine with ethanol gas. You should have replaced any rubber bits by now too due to age.

Ethanol will cause trouble if you leave it set a long while in our old poorly sealed systems. If you plan to do this I'm a big fan of running the carb dry. A shutoff valve would make this trivial before it goes to sleep for the winter. Gas will varnish over time, with or without ethanol.

 

[Blusmbl]

Worth mentioning, even though most musclecar era stuff is listed as 10:1 compression, it rarely is ever close to that in the real world due to manufacturing tolerances on the combustion chamber size and deck heights.

There are many things that can be done to enable lower octane fuel. Loose torque converters, slowing down the mechanical advance, etc.

Modern cars will adapt to fuel octane through the knock sensors, you can run 87 on a true 11.5:1 CR engine, but it pulls timing to do it so you’re down on power and fuel economy compared to if you ran premium. You can do the same thing with our cars, it just requires manual timing adjustment instead.

 

[Ram Fury]

Worth mentioning, even though most musclecar era stuff is listed as 10:1 compression, it rarely is ever close to that in the real world due to manufacturing tolerances on the combustion chamber size and deck heights.

There are many things that can be done to enable lower octane fuel. Loose torque converters, slowing down the mechanical advance, etc.

Modern cars will adapt to fuel octane through the knock sensors, you can run 87 on a true 11.5:1 CR engine, but it pulls timing to do it so you’re down on power and fuel economy compared to if you ran premium. You can do the same thing with our cars, it just requires manual timing adjustment instead.

Lads --
The 426-Street in my '65 Sport Fury has been "up graded" a bit with a non-stock and somewhat wilder cam that now idles at a lope when warm and higher than the conventional 750-850 RPMs. Its console-mounted tach (whose accuracy may be questionable) indicates it can reach close to 6000 RPMs especially with the 3.90s in the rear end. I had the car's virtual twin back in 1964-67 (a 426-S/4-speed, but "un-hopped-up" engine) and as I recall, that 426-S engine was produced to somewhat more careful tolerances than most production mills (although serious racers always "blueprinted" them), so I regard its advertised 10.3:1 CR as legit. I also have experienced the deteriorating effects of high ethanol fuels on the rubber fittings of my '60 SonoRamic Commando Fury, and I always include five gallons of 110 octane leaded racing fuel in every tankful in each of my "musclecars" (i.e., 20 gals. in the '60 Fury and '65 Fuel Injected Corvette, 23 gals in the '57 Chrysler 300C's, and 25 for the '65 SF). The C's heads did not require valve seat hardening for unleaded fuel, but those on the other three did. Of course, the results from octane boost is evident while those from the lead additives less so except in the case of the Vette (its 300 PSI fuel injection pump demands leaded fuel as a lubricant). I suppose if I didn't enjoy flogging them so much I could get by with lower octane and cheaper gas -- "Beamers" and those "Pacific Rim" cars with souped up lawnmower motors are meat on the table.
Joe Godec

 

[Jakter]

I use/used 87 octane ethanol on any car I owned since it was available, stopped at whatever gas station I was near when ever I needed fuel and have not had a problem with it.

I do replace all rubber hoses, rebuilt fuel pumps and carburetors with easy to find ethanol compliant rebuild kits.