Compression question
Thread Starter
Drifting
Joined: Nov 2005
Posts: 1,361
Likes: 0
From: Downriver Mi.
Compression question
Hi,Can anyone tell me what the compression ratio a 58cc head on a stock 85 would be ?What type of piston?, flat top, dished?size of valve reliefs? Thanks for any help.
Last edited by MR NICE; Jan 25, 2006 at 09:59 PM.
Racer
Joined: Sep 2004
Posts: 430
Likes: 2
From: Sellersville, PA
St. Jude Donor '10
There was a thread a while back where I asked the same question, I'll have to find it, but if I remember correct it was around 11:1 or a little bit higher.
Edit:
This was the thread I mentioned.
http://forums.corvetteforum.com/show....php?t=1267605
Edit:
This was the thread I mentioned.
http://forums.corvetteforum.com/show....php?t=1267605
Last edited by newcastle3; Jan 26, 2006 at 11:08 AM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I forget the final answer, but if you make some assumptions, you can figure it out, yourself, pretty easily. The '85 has a 9.0:1 compression ratio. If you can accept that spec as fact, knowing that the 350 has a 4.00" bore and a 3.48" stroke, you can work backward to figure the above piston volume at TDC. Subtract the 18 ccs, (the difference in the stock 76 cc heads and the 58 cc heads you want to install), from the above, figured above piston volume at TDC, and re-figure the compression ratio. That way you don't have to know a lot of sometimes difficult to obtain figures, like piston valve relief volume, etc. This method DOES assume the same head gasket volume, but you can adjust for that, too, if you have the numbers. Simple, EH?
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RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by MR NICE
Thanks,is 11to 1 safe with 93 pump gas?I think I'll go with 64 cc. to be safe.
You can go through the same exercise, I described above, for 64 ccs, also.
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Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
Check out the this compression calculator, there is a free demo version 
http://www.performancetrends.com/download.htm#crc
http://www.performancetrends.com/download.htm#crc
Advanced
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