Compression test results Before and after
Thread Starter
Race Director
Joined: May 1999
Posts: 14,267
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From: Plymouth MI Formerly Milford, MA MI
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Compression test results Before and after
What do you think
5/12/1999 108k 9/25/2002 135k
1 205 219
2 208 200
3 200 232
4 210 222
5 210 231
6 214 215
7 210 220
8 210 225
:confused:
5/12/1999 108k 9/25/2002 135k
1 205 219
2 208 200
3 200 232
4 210 222
5 210 231
6 214 215
7 210 220
8 210 225
:confused:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Compression test results Before and after (L98Terror)
Looks ok for 135k miles. The difference from highest to lowest compression is on the high side, but not worth doing anything about it.
Thread Starter
Race Director
Joined: May 1999
Posts: 14,267
Likes: 1
From: Plymouth MI Formerly Milford, MA MI
W. Detroit Events Coordinator
Cruise-In VI Veteran
Cruise-In VII Veteran
Cruise-In VII Autocross Champ
Re: Compression test results Before and after (ski_dwn_it)
How did they increase? Ho/cold engine? Different guage?
The #3 had the highest and was the one I pulled the funky plug out of. maybe it'e pushing oil causing a better seal or filling the chamber a little????
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
Re: Compression test results Before and after (L98Terror)
A compression test doesn't tell you a whole lot in the whole scheme of things. It can't tell you anything really more than how your cylinders compare with each other.
You really need a leakdown test for good info. This will test to see how the entire cylinder seals. I did a compression test on mine, in which case the motor is perfectly healthy and it made right around 140 on all cylinders. The leakdown test showed a different story however, to the tune of 50% leakdown on the #4 cylinder while all the others were less than 2 percent. The problem was that my exhaust valve wasn't sealing for some reason.
Now that I've got my new heads and new valves installed I need to do it agian and see what I come up with. It makes 365 horsepower so I'd say it will be pretty good. :D
You really need a leakdown test for good info. This will test to see how the entire cylinder seals. I did a compression test on mine, in which case the motor is perfectly healthy and it made right around 140 on all cylinders. The leakdown test showed a different story however, to the tune of 50% leakdown on the #4 cylinder while all the others were less than 2 percent. The problem was that my exhaust valve wasn't sealing for some reason.
Now that I've got my new heads and new valves installed I need to do it agian and see what I come up with. It makes 365 horsepower so I'd say it will be pretty good. :D
Burning Brakes
Joined: Jan 2001
Posts: 1,169
Likes: 0
From: Manhattan
Re: Compression test results Before and after (L98Terror)
i'd say comparison between the tests will tell you nothing, but comparison of the cylinders of todays test shows #2 a little weak. did you test #2 again to make sure the results aren't skewed?
the next thing i'd do is a leakdown test, because #2 doesn't look too healthy. :(
the next thing i'd do is a leakdown test, because #2 doesn't look too healthy. :(
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Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: Compression test results Before and after (jfb)
I have to agree with Nathan. After posting this morning on the increase, I thought I should have also mentioned the leakdown test.
I recently just found out my rings were leaking on my 350. They tested the drivers side only and found them all to be leaking at least 20%. One was as high as 50%! They did not bother doing the other side, no real point, the engine needed refreshed.
When I did my compression tests, on several different occasions, both hot and cold. ALL my cylinders were within +/- 2 PSI of one another! This would indicate a very tight engine or a very uniformly worn engine, which in my case is exactly what I had.
I also had a very small about of the ash deposits on my SP. That is a real good indication of OIL getting past the rings. I also had blowby that was seen around all the breathers in the vavle covers, and also when the oil fill was taken out when the engine was hot, you could see puffs of smoke coming out while the car idled.
I suspect a leakdown will yeild the answer you are not really looking for, but the right one. :confused:
LAter :cheers:
I recently just found out my rings were leaking on my 350. They tested the drivers side only and found them all to be leaking at least 20%. One was as high as 50%! They did not bother doing the other side, no real point, the engine needed refreshed.
When I did my compression tests, on several different occasions, both hot and cold. ALL my cylinders were within +/- 2 PSI of one another! This would indicate a very tight engine or a very uniformly worn engine, which in my case is exactly what I had.
I also had a very small about of the ash deposits on my SP. That is a real good indication of OIL getting past the rings. I also had blowby that was seen around all the breathers in the vavle covers, and also when the oil fill was taken out when the engine was hot, you could see puffs of smoke coming out while the car idled.
I suspect a leakdown will yeild the answer you are not really looking for, but the right one. :confused:
LAter :cheers:
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Compression test results Before and after (L98Terror)
#2 certainly looks a little funky - bad valve(s) maybe? - I'd reject it hot and you can minimize the chances of stripping any plug threads by loosening the plugs when the engine is cold and just leaving them finger tight or a bit tighter while the motor warms up.