Compression test? (1 Viewer)

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I was just doing a compression test on my LC this afternoon, and I got some pretty good results with 171K and going.

My question is that in the instruction booklet, that came with the compression tester, said that a normal engine(non high compression motor) should be cranked 6 times, whereas a High Comp engine should be cranked 10 times.

When I done both it gave me the following results:

6 times

Cylinder 1- 167 psi
Cylinder 2- 171 psi
Cylinder 3- 174 psi
Cylinder 4- 172 psi
Cylinder 5- 174 psi
Cylinder 6- 176 psi

10 times

Cylinder 1- 169 psi
Cylinder 2- 174 psi
Cylinder 3- 175 psi
Cylinder 4- 176 psi
Cylinder 5- 175 psi
Cylinder 6- 179 psi

Which should I go by? All are pretty good #'s though (FSM has 171 psi as good and all cylinders should be within 14 PSI of eachother)
 
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The tests are really too close together to see any difference between the two. You could go by either one.

Everything looks good, cylinder 1 is slightly low so might be something to keep an eye on but nothing to worry about.

Now if you want to be really OCD, go and do a leakdown test. :hmm:
 
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Your findings are interesting. I thought typically cylinder 6 on these engines usually had the lower numbers because that it where the HG fails most often, and that is where most of the damage occurs.
 
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Your findings are interesting. I thought typically cylinder 6 on these engines usually had the lower numbers because that it where the HG fails most often, and that is where most of the damage occurs.

6 is the most common, but I've read more than one case of it failing on 1 as well.

I doubt that the low numbers are due to a failing HG, however. More likely just typical wear and tear.
 

e9999

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I would not worry much about something like +-5 psi variation, frankly
 
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I have a 30PSI drop in #5. I guess I AM an individual after all.

In my case its the valves. It still runs OK, but I am fixing it, in the next couple of weeks.

Mark
 
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I guess that I'll just use the first numerical value. Thanks for the info. Maybe next I'm going to do the leak down test.

Although I'm not too worried about it because of the numbers that I got.

I am amazed with this motor. I bought it from a family member that only changed the oil every 3k, and maybe a tune-up here and there.

And with 171psi and greater is just amazing to me. I was worried about maybe a HG going out with those miles and not being up to spec as I would take care of the LC, but everything seems to be doing just fine now (with my OCD)....
 

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Both sets of numbers are fine. Don’t worry about #1, it’s a few less. No worries. Drive it like you stole it.
 

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