How much C/R can one run on 91 octane pump gas?, Type 4 specific. Options

[Aaron Cox]

Strong possibility that the heads are coming off my 2L beast. while they were off, i figure i will bump up the CR to sneak some HP out.

MY motor has headgaskets and euro 94mm p/c (flat top mahles)
i think it is a tad over 8:1 currently.

been 3 years since i built it - runs great.

so my thinking is, remove the base shims and headgaskets -

I will CC the heads while they are out (cant recall the data when we built it 3 years ago)

How little deckheight can i run? what is max CR i can run on 91 premium unleaded?

If it matters, have mallory dizzy (can back off total advance if it detonates etc..) mallory CDI, and cool b7es NGK plugs.

AA

[sean_v8_914]

here is a link to a compression calculator.

http://www.btinternet.com/~mezporting/header.html

ditch teh head gasket and lap teh cylinder into the head. teh factory posted a bulliten to eliminate teh gasket. are you running a stock cam? valve lift and how deep your heads and or chambers are cut will dictate how low you can set teh deck. 0.040 is a good starting point of reference for deck.

a compression quote might launch a huge debate...
my 8.5 CR did not ping with 89 octane

how thick are your cylinder base shims?