alright i just bought a new motor with: 02 tranny, corilla push rod, high compression piston (11-1compression), powercoated water pump cover, LRD full race cam, barnett dirt digger clutch, all new bearings, carbs are taper bored. the guy said he ran 112 oct race fuel but it will run with 50/50 mix of 94 and 112. isn't 112 a lil over kill? 103 oct would be good right?

 

For 11:1 dynamic compression? My elevation is 500' and I never had a problem with premium 93 octane pump gas. If you want to run 95 or 98 thats fine, but 112 is ignorant and 103 is overkill. That was with a less aggressive cam, which yields more compression. I've got a more aggressive camshaft now, and still no problems.

JMO.

 

Hell run aviation fuel let it fly? lol j/k? you dont want to mix it will run like you got spyware on you computer? lol

 

Yeah, mixing pump gas with race gas is no good, neither is mixing avgas with other fuels. Dont run avagas either, unless you can test the 100LL and find out exactly what its putting out at your elevation.

 

I think that 110 off road use will do the trick bud? with those mods?

 

run the lowest octane you can without detonation or heating problems. The lower the octane the faster the burn the more power you will get. But with higher compression it makes more heat and causes detonation so you need a slower burning fuel (higher octane)to resist the tendency to ignite before the spark. Since you are running an 11:1 piston you can use regular pump gas 91-93 octane and you should have no problem.


That was with a less aggressive cam, which yields more compression.

how does a cam affect your compression????

 

Not so much the cam, as the valve work done in accordance with it. More aggressive camshafts usually means more head porting, decreasing compression because there is less material in the chamber. But a longer duration can allow less time and chance for pre-combustion and detonation.

 

Cams can't effect static compression. But they effect air capture rate, and that can effect detonation in a big way. Valve timing and overlap can effect air capture in a big way.
That is why an engine does not detonate at idle. You are effecting the capture rate of the air by the throttle. Not much air, not much bang, no detonation. WOT='s lots of air, which ='s detonation in a tight squeeze engine burning low octane fuel.
That's why turbo/blower engines detonate. More air ='s tighter squeeze and more chance of detonation.

RAPTOR2FAST4U run pump gas in a true 11 to 1 motor; you will be fine.

 

Ok I got you maddog56, you always seem to know your stuff, so you threw me when I thought you meant the cam on it's own.

 

the higest oct we got at our pumps here in alaska is 91....what shoudl i do about that? or will that be fine?