l134 fuel choices/performance

[MikeP]

so i got to thinkin and was wondering if there is any real noticeable improvements to our l134 engines (more hp, better mpg etc) when using lower or higher octane fuels and whether or not the additives in the higher octane fuel helps any with our classic engines and if anyone has done any sort of testing id love to see it

[oldtime]

The 134's were designed to run on uncracked gasoline which has an octane rating of 67.
So that directly implies there is no advantage if burning a higher octane fuel.
In other words these low compression engines cannot take advantage of octanes above 67.
So if your burning the typical 87 octane fuel, know that the Willy's 134's are wasting the extra octane due to low the low compression ratios

[MikeP]

thats interesting to know and lets say i picked up a supersonic head and raised my compression some would i then see a gain or would it be marginal at best and i already know about the ethanol junk and i plan to use lucas safeguard ethanol conditioner to help  https://www.walmart.com/ip/LUCAS-OIL-10576-Safeguard-Ethanol-Fuel-Conditioner-16-Ounce/17491940

[oldtime]

Raising the 134 Willys CR is bad if you want to use a hand crank starter.
Raising the CR is good if you want to get an increase from the fuel you burn.
Absolutely no reason to burn any octane higher than our common typical  87 octane gasoline.

So long as the fuel octane does not cause pre-ignition you can increase the CR to get more bang for your buck.
Engines generally begin to pre-ignite when octane is 10 times the CR or higher.
In other words you can typically operate an engine at 8.7 to 1 CR on 87 octane or 9.3 CR with 93 octane gasoline.
This octane to CR ratio is not an exact and hard fast rule.
It's merely a basic observation.

An F-134  Hurricane with a very rare high compression head (intended for use above 10,000 elev.) is right near 7.8 / 1 CR.
7.8 / 1 CR is still a long ways from using all of the octane available in today's  low octane fuel.