compression question
Thread Starter
|
Senior User
Joined: Apr 2003
Posts: 123
Likes: 0
compression question
Howdy all,
I've got a question about compression. My manual says my '87 302 had 8.9:1 when it was new. I tried to figure out what that means in PSI. I took pie x bore radius squared then multiplied that by the 3" stroke. Once I'd figured the cylinder bore and stroke volume, I multiplied that by the 8.9 compression ratio number. I got a bit over 335. That can't be at all right. My compression is sitting between 175psi and 185 psi.
Does anyone know the stock psi compression of this 302? The proper equation would be nice too.
Any info will be greatly appriciated!
-John R.
I've got a question about compression. My manual says my '87 302 had 8.9:1 when it was new. I tried to figure out what that means in PSI. I took pie x bore radius squared then multiplied that by the 3" stroke. Once I'd figured the cylinder bore and stroke volume, I multiplied that by the 8.9 compression ratio number. I got a bit over 335. That can't be at all right. My compression is sitting between 175psi and 185 psi.
Does anyone know the stock psi compression of this 302? The proper equation would be nice too.
Any info will be greatly appriciated!
-John R.
Posting Guru
Joined: Aug 2002
Posts: 1,214
Likes: 2
From: Minneapolis, MN
compression question
This has been discussed before. You can't determine the compression ratio by the cranking pressure and vice versa. There are too many variables such as ring seal, cam overlap, cranking speed, etc. The compression ratio is the difference between the volume of the cylinder combined with the combustion chamber at TDC and BDC.
175 to 185 cranking sounds like a good tight engine to me.
175 to 185 cranking sounds like a good tight engine to me.
Freshman User
Joined: Mar 2002
Posts: 29
Likes: 0
compression question
Good day,
After much searching I found something of some use on the internet. Its a chart that compares Compression ratio to PSI.
http://www.geocities.com/terminalvelocitycoaster/adr/
/\/\()|\|z@
After much searching I found something of some use on the internet. Its a chart that compares Compression ratio to PSI.
http://www.geocities.com/terminalvelocitycoaster/adr/
/\/\()|\|z@
Thread
Thread Starter
Forum
Replies
Last Post
c2z4s9
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
73
Feb 29, 2016 07:14 AM
FatMike86
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
9
Jul 20, 2002 06:16 PM
skipper
Big Block V8 - 385 Series (6.1/370, 7.0/429, 7.5/460)
4
Jan 9, 2002 11:03 AM
