Is this good?

Five0 · 12-13-2001, 07:07 PM

I ran a compression test and these are the #'s I got.
1. 150
2. 155
3. 155
4. 155
5. 160
6. 155
7. 160
8. 160

Is that good or bad; the motor has about 3000 miles on it.
I have a 347 with 10 to 1 compression.

I think it is pretty good but want a second opinion.

lx mike · 12-13-2001, 08:03 PM

it is very good. what your looking for is any cylinder that is much lower than the others.

Five0 · 12-14-2001, 08:40 AM

That is what I thought, thanks mike.

exgmguy · 12-14-2001, 01:59 PM

Consistency is good, but my stock compression motor makes 155-160 across the board. A friends LT1 shows 180 psi and they are 10.25 to 1.

Maybe you might want to try a leakdown?

exgmguy · 12-14-2001, 02:02 PM

I think the overlap of any given cam may also affect compression numbers, so being you have a 347, it probably has a decent cam and you probably don't have anything to worry about.

Did you check the compression when the engine was at operating temperature? A warm engine is usualy good for another 10 psi or more.

Five0 · 12-14-2001, 06:37 PM

It was warm but not hot.
The cam is a 224/230@0.050 with .544lift 112ls

I do not know anyone around here that has a leak down tester.

12-13-2001, 07:07 PM	#1
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	Is this good? I ran a compression test and these are the #'s I got. 1. 150 2. 155 3. 155 4. 155 5. 160 6. 155 7. 160 8. 160 Is that good or bad; the motor has about 3000 miles on it. I have a 347 with 10 to 1 compression. I think it is pretty good but want a second opinion. __________________ James Cox RHC Member #44 nochevy@hotmail.com 1991 Mustang LX Dart iron eagle block, 4340 28oz 347 crank, 4340 h-beam rods, probe ultra light pistons canfield heads “race ported by Brent Frazier”, solid roller cam and lifters “custom grind”, kooks 1 7/8" race headers, and much more. Engine built by Brent Frazier.

12-13-2001, 08:03 PM	#2
lx mike Undescribable Join Date: Sep 1998 Location: Ft Myers Fla Posts: 1,539	it is very good. what your looking for is any cylinder that is much lower than the others. __________________ Rice Haters Club Member #101

12-14-2001, 08:40 AM	#3
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	That is what I thought, thanks mike. __________________ James Cox RHC Member #44 nochevy@hotmail.com 1991 Mustang LX Dart iron eagle block, 4340 28oz 347 crank, 4340 h-beam rods, probe ultra light pistons canfield heads “race ported by Brent Frazier”, solid roller cam and lifters “custom grind”, kooks 1 7/8" race headers, and much more. Engine built by Brent Frazier.

12-14-2001, 01:59 PM	#4
exgmguy Registered Member Join Date: Feb 1999 Location: Utica, Michigan Posts: 2,631	Consistency is good, but my stock compression motor makes 155-160 across the board. A friends LT1 shows 180 psi and they are 10.25 to 1. Maybe you might want to try a leakdown? __________________ 1988 Mustang GT stock bottom 302, C4 10.9 @ 128 with 8 psi of Novi 1000 boost!----STOLEN 1989 Mustang notchback Warmed up 306 with a Procharger.

12-14-2001, 02:02 PM	#5
exgmguy Registered Member Join Date: Feb 1999 Location: Utica, Michigan Posts: 2,631	I think the overlap of any given cam may also affect compression numbers, so being you have a 347, it probably has a decent cam and you probably don't have anything to worry about. Did you check the compression when the engine was at operating temperature? A warm engine is usualy good for another 10 psi or more. __________________ 1988 Mustang GT stock bottom 302, C4 10.9 @ 128 with 8 psi of Novi 1000 boost!----STOLEN 1989 Mustang notchback Warmed up 306 with a Procharger.

12-14-2001, 06:37 PM	#6
Five0 Registered Member Join Date: Apr 2000 Location: middleburg, fl, usa Posts: 1,134	It was warm but not hot. The cam is a 224/230@0.050 with .544lift 112ls I do not know anyone around here that has a leak down tester. __________________ James Cox RHC Member #44 nochevy@hotmail.com 1991 Mustang LX Dart iron eagle block, 4340 28oz 347 crank, 4340 h-beam rods, probe ultra light pistons canfield heads “race ported by Brent Frazier”, solid roller cam and lifters “custom grind”, kooks 1 7/8" race headers, and much more. Engine built by Brent Frazier.

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