12 to 1 compression
12 to 1 compression After doing some research I found that with my set-up a .039 head gasket and milling my heads down to 52cc I can achieve 12 to 1 compression is this still a safe compression to run on 93 pump gas on the street.
http://www.rbracing-rsr.com/comprAdvHD.htm
you should be able to get away with it as long as your cam closes the intake valve at or after 72 degrees abdc.
good tune and a good working cooling system and you should be fine. do you have 93 octane or 91 octane where you live?
you should be able to get away with it as long as your cam closes the intake valve at or after 72 degrees abdc.
good tune and a good working cooling system and you should be fine. do you have 93 octane or 91 octane where you live?
Yep its the dcr you need to figure. For a good read on dcr and a dcr calculator go here dcr calculator.
In addition to what zigroid mentioned a good quench will help too.
In addition to what zigroid mentioned a good quench will help too.
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Originally Posted by matt94z
It turns over just fine. LT1's love compression. BTW your using the same setup on your 355 as I have.
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I was wondering about mine. I'm now on a .0 deck with the piston .005 in the hole, i'm using a the .26 impala gasket if i can find some, If not .28. I have a 54cc head and -4.8 cc Flat tops. I hope i can pull off 91 cause no 93 on this state 
ok lol i am messing something up on my DCR never was good at math.
Given my set-up in my sig a zero decked block. .039 gasket and 52cc chambers what would be the DCR if i was using the gm847. i don't plan to use this cam I am going with a custom grind that might be similar so i just want to see what turns out.
Given my set-up in my sig a zero decked block. .039 gasket and 52cc chambers what would be the DCR if i was using the gm847. i don't plan to use this cam I am going with a custom grind that might be similar so i just want to see what turns out.
i was getting something like int he 10s lol i was putting in the wrong numbers though
I am going with a custom I will have it spec'd after i have my heads done so i am not really worried that my DCR will be bad i was just worried that something a little big like that would give me to high of a DCR. It seems that 8.5 is what i should keep it around or a little under. so I guess if I used the 847 it would be good I am still set on custom though. did you do the calculation with 1.5 or 1.6rrs i forgot to add i was using them.
I am going with a custom I will have it spec'd after i have my heads done so i am not really worried that my DCR will be bad i was just worried that something a little big like that would give me to high of a DCR. It seems that 8.5 is what i should keep it around or a little under. so I guess if I used the 847 it would be good I am still set on custom though. did you do the calculation with 1.5 or 1.6rrs i forgot to add i was using them.
Last edited by 95FbFormula; Jun 14, 2007 at 11:31 PM.
As long as you have either enough cam to bleed off the compression and / or not a lot of timing it should be fine. Another thing that shouldn't be overlooked also is an adequate cooling system. High compression motors get hot and usually stock isn't up to the task of cooling it down.
Lift has no affect on dcr. Dcr is determined by the pistons location at intake valve closing. For example a stock cam would close the intake valve with the piston much closer to bdc therefore would have a higher dcr than a larger aftermarket cam because the piston would be up higher when the valve closes.
Also the lobe profile has to be considered too. For instance I was going to use the comp 503(224/230) cam but it pushed my dcr around 9.0. So I went with the gm846(222/230) and with its lazier lobes it made my dcr at 8.5. I hope this makes sense I can barely keep my eyes open, so I'm going to bed.
Also the lobe profile has to be considered too. For instance I was going to use the comp 503(224/230) cam but it pushed my dcr around 9.0. So I went with the gm846(222/230) and with its lazier lobes it made my dcr at 8.5. I hope this makes sense I can barely keep my eyes open, so I'm going to bed.
