Deciphering new compression results?

[hob]

I completed a first compression test because of a cooling issue I was having and wasn't pleased with the compression results. For the time being I believe I've solved the cooling issue and do not believe it was in result of the compression #s. Also I haven't found any smoking, stumbling, misfires, or CELs. It runs solid and feels generally strong.

Tonight I've completed my second compression test with a warm engine / WOT which I didn't do for the first test and results changed to be a little more consistent.

#1 170
#2 168
#3 160
#4 165
#5 135
#6 135
#7 130
#8 138

Passenger bank is good, driver bank is all low. With no other indications (smoking misfires ect) is it still possible my engine has four damaged piston/rings all within that close of each other in compression on the same bank? Should I be thinking there's a timing issue here instead? I've read something of these cars "skipping a tooth" messing up the timing?

Hoping I can be schooled in what I'm seeing with these results and where to go from here.

 

[oldmodman]

I doubt that four pistons would be damaged. It's most likely that the drivers side bank has one (or both) cams mistimed.
It could have just been assembled that way due to all the various parts all being a little off, and all in the same direction. Could be a worn, or failed tensioner on that bank too. It's amazing how much just a few degrees off between the intake and exhaust cam can have on cranking pressure. It's just too bad that it's so damn difficult to degree them while in the car. Not impossible, but a colossal pain in the ass.

 

[racebronco2]

The chains just stretched, especially at 100,000 miles. I have seen then stretch at 70,000 miles. I wouldn't worry about it. Just drive the car.

 

[Mystic03]

salvage the block/crank send it in to be built! thats what im doing

 

[hob]

The chains just stretched, especially at 100,000 miles. I have seen then stretch at 70,000 miles. I wouldn't worry about it. Just drive the car.

salvage the block/crank send it in to be built! thats what im doing LOL

Quite different directions for me to take there. I may call around tomorrow to see shops charge to adjust timing (or if they think something else is at play).

Although still not sure how to go about this one... Thanks for the suggestions so far.

 

[hob]

I'd be curious to know if/how much I'd be down on power with these numbers as well

 

[Ourobos]

How about a wet compression test?

 

[DSG2003Mach1]

Quite different directions for me to take there. I may call around tomorrow to see shops charge to adjust timing (or if they think something else is at play).

Although still not sure how to go about this one... Thanks for the suggestions so far.

its probably not gonna be cheap, Id imagine to do it right you need all new chains, guides and tensioners, which means taking everything off the front of the motor, timing cover off and lifting the valve covers (not sure if they have to come all the way off)

 

[racebronco2]

Just drive the car, any high mileage car will be close. The owners just haven't taken a compression test.

 

[ctgreddy]

^ His results are not normal tho. Most higher mileage cars will be off by a decent amount but not like that, like some will be 165 some will be 150. Not everything within 5psi yet one bank being 30psi more. That to me means something is off. Very well could be timing even tho it seems highly unlikely that it's jumped but hasn't jumped enough to mess anything up. I'd do a leak down on it next. That'll tell you if anything else is at play, wether that be head gaskets, rings/pistons, valves, etc. if it passes all that then I'd start looking into the timing idea.

 

[hob]

Yea that's what I'm afraid of. I had a cheap leak down tester but the adapter was too large to fit into the spark plug screws, so I wasn't able to get those results. I've got to find another.

 

[ctgreddy]

Yea that's what I'm afraid of. I had a cheap leak down tester but the adapter was too large to fit into the spark plug screws, so I wasn't able to get those results. I've got to find another.

You should be able to use the same hose that you used on the compression tester, only thing you'll have to do is remove the schrader valve from the end of the compression tester hose.

 

[hob]

I haven't drove the car much lately or much less taken it to a speed shop yet to analyze this issue, but I'm wondering if it isn't a timing issue and it is in fact bad pistons, would they likely tell me to replace the block rather then spend the time/money to fix four damaged pistons?

 

[TRBO VNM]

1 tooth can be 20psi. It was for me on a MMR motor. Add 20psi to the low bank and then they don't looks so bad, huh?

 

[gmtech]

Should have added a little oil to each low cylinder and retest, to check for ring wear. Then complete a leakdown test to see if it has excessive leakdown. But i do agree that since every hole on that side is low, appears to be a timimg issue. Good luck