Milled 62 cc AFR's,Compression & Deck Height
Thread Starter
TECH Regular
Joined: Aug 2003
Posts: 414
Likes: 0
From: Berkley, MI
Milled 62 cc AFR's,Compression & Deck Height Ok ...I will paraphrase how it is going down on a great but less technical site: Evidently per a members call to AFR "deck height variance" led to the following problem: Compression way to high (not sure how high) which = extreme detonation on pump gas. This was on an AFR built LS engine where the AFR 66 cc heads were milled .30 to get 62 CC and 11:1 compression.
--- Note: AFR 66cc "stock" compression = 10.25:1.
The solution is to check deck height and then work backwards with gasket thickness and the milling to get the ideal (in my case 10:9-11:1) compression and avoid unwanted super high compression and detonation on 93/4 octane.....or way to low compression. Seems like a lot of work. I want to go milled .30 for the 62 CC and use a stock gasket (not certain of its exact thickness) & unless I have an “extreme” "deck height variance" on the low side I hope to be fine with no detonation & "about" 11:1 compression (or close to it) on 93 octane. P/V clearance should not be an issue with a lift of .566 (I hope). My adv. duration is 286 and duration @ 50 = 222.
What do you guys think of that ?
Has detonation due to unwanted "high" compression been an issue with you guys running milled heads ? I did not want to have to worry about a variable such as deck height.
RAGE OR DIE
--- Note: AFR 66cc "stock" compression = 10.25:1.
The solution is to check deck height and then work backwards with gasket thickness and the milling to get the ideal (in my case 10:9-11:1) compression and avoid unwanted super high compression and detonation on 93/4 octane.....or way to low compression. Seems like a lot of work. I want to go milled .30 for the 62 CC and use a stock gasket (not certain of its exact thickness) & unless I have an “extreme” "deck height variance" on the low side I hope to be fine with no detonation & "about" 11:1 compression (or close to it) on 93 octane. P/V clearance should not be an issue with a lift of .566 (I hope). My adv. duration is 286 and duration @ 50 = 222.
What do you guys think of that ?
Has detonation due to unwanted "high" compression been an issue with you guys running milled heads ? I did not want to have to worry about a variable such as deck height.
RAGE OR DIE
Thread Starter
TECH Regular
Joined: Aug 2003
Posts: 414
Likes: 0
From: Berkley, MI
Yes, I suppose. I hate to do a head swap and have less compression than stock with $2000 + heads on an N/A engine though. It's only like 80 bones to mill them for 8-9 hp across the board - as far as cost per HP thats reasonable. Most of the distributors are moving milled 62 cc units. I guess I'll just have to figure this out.
