How much C/R can one run on 91 octane pump gas?, Type 4 specific. |
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How much C/R can one run on 91 octane pump gas?, Type 4 specific. |
Aaron Cox |
Apr 22 2006, 09:37 PM
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#41
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
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 |
Apr 22 2006, 10:09 PM
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#42
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Chingon 601 Group: Members Posts: 4,011 Joined: 1-February 05 From: San Diego Member No.: 3,541 |
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? |
Aaron Cox |
Apr 22 2006, 10:21 PM
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#43
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
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? lapping cyl's to heads goes without saying. i have a big cam, i believe a web 494 or an 86 grind. 3000 is about the beginning of the powerband. do nott recall actual lift numbers (had a folder with the build notes, and cannot find it) base shims are anybody's guess without the build notes.... stock rocker ratio...... AA |
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