Posted by T.L. (IP: 206.133.171.100) on August 09, 1999 at 11:56:23:
In Reply to: A little clarification... posted by TBR on August 06, 1999 at 13:18:01:
He's talking about a RACE CAR, not the typical street-driven Mavericks & Comets that we drive everyday...As far as timing; it's the TOTAL advance that should concern you the most (usually around 2500-3000RPM)...You should NEVER exceed 38 degrees on a 302...Altitude also affects "knocking"...where I live, the altitude is high and we don't need high octane gasoline, I run 14-deg. initial timing and 38 total and have NO knocking with the cheapest regular gas....I have run 115-octane racing fuel in my stock 8:1 motor and there was NO DIFFERENCE in performance...
: ...As TParker wrote: "The only thing higher octane does is reduce pre-ignition". You take a low compression engine (8.5:1) and dial in initial advance of 10 degrees it will run just fine. Bump the timing to 16 degrees and it will knock like crazy. You have just raised the "effective cylinder pressure" and fooled your engine into thinking it is a high compression unit. Add premium and that will most likely stop the knock. However running that much advance will generally not help the engine - the plugs will run hotter & probably burn up. Power will fall off accordingly. There is too much of a good thing;-)
: : in a racecar i used to run with a mopar 360 we used VP Purple Racing Fuel. the motor was a stock 8.5 to 1 comp. ratio and when we used the purple stuff the motor would run about 10-15 degrees cooler and we got about 100-200 more rpm out of it....