cubs & pump gas

[stew2272]

Hi everyone im planing on building a 421 cub motor buy my only concern is will i be able to run it on super unleaded 97octane as that's all we can get over here in England or just regular unleaded my elevation is 350ft to 500ft above sea level and the tempreature is around 40 to 70 degrees some people say that cubs don't like pump gas so i thought someone can help me out as i don't want to throw money into someyhing that ain't gona work or screw up the motor?

[BigRed350x]

Hi everyone im planing on building a 421 cub motor buy my only concern is will i be able to run it on super unleaded 97octane as that's all we can get over here in England or just regular unleaded my elevation is 350ft to 500ft above sea level and the tempreature is around 40 to 70 degrees some people say that cubs don't like pump gas so i thought someone can help me out as i don't want to throw money into someyhing that ain't gona work or screw up the motor?

 

It depends on how much compression you throw at it. If you are under 155psi you will be safe with 93 octane. I'm not sure what the cutoff is for 97 octane, probably close to 170psi. You will be fine running it with pump gas, just watch your compression.

 

I run mine on 93 octane, but I'm at 7500ft.

[Animalman294]

It's not really dependant on your cubs, it is the compression that the motor builds that determines whether you can run pump gas, AV 100LL, or race gas. If it is above 155 you need to be running a higher octane fuel to keep the cylenders from detonating (ie, prolonged abuse - holes in pistons). So first you need to check your compression and see where that is at. It also depends on the rest of your mods, but start there once you build the motor............. :beer:

[stew2272]

Thanx guys for the excellent advice much appreciated