If I were to run an aluminum head race motor with 12 to 1 compression on the street, how much 110 octane race fuel would I have to add to 91 pump premium to eliminate preignition? Steve

Steve,

Depends on alot more information then you gave. Stroke affects Detonation. A 12/1 428 will detonate before a 12/1 427. Combustion chamber affects detonation. Engine cooling system affects detonation. Camshaft will affect detonation.

Not a simple one answer question.

Roger

...quite a lot on the street on 91 octane California "clean air" gas. It had Edelbrock heads and a 308R Comp roller. No audible "ping", but you had to put 'er in gear sometimes to get it to shut off. If you can keep engine coolant temp below 190*, it's a great help.

I wouldn't reccomend any full-throttle "wicks" without "spike'n" the gas 50/50 with some 110.

but as already stated, many variables exist so no mere table or chart will truly suffice. Best to start with the highest octane one can reasonably achieve and slowly take it down from there.

http://www.daytona-sensors.com/tech_tuning.html

I put about 7K miles on my 511" FE, with about 12:1 static compression, and ran it all on pump premium. I only added race gas at the track. If your intake valve closes late enough, you shouldn't have to add any race gas to the mix to run on the street.

Jay Brown
1968 Shelby GT 500 Convertible, 492" 667 HP FE
1969 R code Mach 1, 490" supercharged FE, 9.35 @ 151.20, 2007 Drag Week Runner Up, Power Adder Big Block
2005 Ford GT, 2006 Drag Week Winner, 12.0 Daily Driver
1969 Ford Galaxie XL, 460 (Ho Hum....)
1964 Ford Galaxie 500, 510" SOHC