Compression test help

[mkbubs]

so I did a compression test on my 440 today. Wanted to get some feedback on my findings and what it could mean. On the driver side on all four cylinders I got 150-155 psi, seems good to me. On the passenger side starting at the number 2 cylinder I got 120 psi, #4 135 psi, #6 140 psi, and #8 cylinder I got 150 psi. I didn't run the engine first, forgot to. But from these results it looks like a blown head gasket. Thoughts? Thanks for the help.

 

[khryslerkid]

What made you want to preform a compression test?
How many miles is on your engine?

 

[mkbubs]

Getting a lot of blow bye. No miles on it. The motor was rebuilt about 10 years ago. Then it sat for a few years. I then replace all the gaskets and seals in the motor in 2011. Also having some valve train noise and low oil pressure. All oil pressure components are new Milodon.

 

[multipleBs]

Hi mkbubs:

Though it's possible I wouldn't necessarily suspect a head gasket leak with those pressure readings. That much variation would be possible on a high mileage engine just due to variations in valve seat conditions etc. It almost sounds like the head on the left bank got a valve job and the right bank did not. You mentioned some valve train noise, was it on the same bank as the low pressure readings, or is it hard to tell where it's from? A couple of cam lobes could be wiped out causing both the noise and odd compression readings. The other question I would ask is did you have the rebuild actually done or were you told it was rebuilt by someone who sold it to you? A lot of blowby and no miles on it don't really go together if it was truly rebuilt unless the rings haven't seated properly or there was a problem with the rebuild. The only reason I think about wiped cam lobes is it sat for a long time, so you have to wonder about things like proper cam break in, prelube etc. Just throwing some ideas out there, you could be right and it might just have a gasket issue.

 

[khryslerkid]

I'm wondering if it just needs to break in some to get rid of the blow by?
Noisy valvetrain would be the result of the low oil pressure. Hydraulic or solids?
How low is the pressure? Maybe remove the check valve and check for debris.

 

[miller]

Really sounds like you've got a good reason to pull valve covers, or at least the one on the poor bank. What oil pressure are you getting?

 

[lewtot184]

do a cylinder leak down test to verify where the blow-by is coming from. most likely rings but you'll never know without the test. a by product of combustion is water so without a pcv valve some vapors may get past the rings and pass up thru the breathers.

 

[mkbubs]

i put new lifters and push rods in about a month ago thinking that was the problem. I also talked to a machine shop and they think the push rods are the wrong length. also they think the head gasket is blown, but they haven't seen the engine. just by what I have told them. not sure how you do a cylinder leak down test, what is the proper way to do it? thanks

 

[Shorthorse]

i put new lifters and push rods in about a month ago thinking that was the problem. I also talked to a machine shop and they think the push rods are the wrong length. also they think the head gasket is blown, but they haven't seen the engine. just by what I have told them. not sure how you do a cylinder leak down test, what is the proper way to do it? thanks

Here's a place to start.
http://www.hotrod.com/how-to/engine/116-0406-cylinder-leakdown-tester/

 

[miller]

If your pushrods are the wrong length, that could explain both blow-by, and poor compression...some valves not closing all the way?

 

[multipleBs]

Assuming you replaced a full set of lifters and push rods why wouldn't both banks be affected? The problem only exists on one bank.

 

[mkbubs]

so I did a leak down test on the two cylinders with the lowest compression. on cylinder #2, after pumping it full of air, I smelled fuel and also heard air coming from the carb. Put my hand over it and sure enough, I could feel the air coming out. I only pumped in around 50psi. I then did the same thing to the next cylinder (#4), this time the air was coming from the dip stick. if I'm not mistaken, this means either I need new rings or the cylinder wall is messed up in some form or fashion. Thanks for the help guys.

 

[moper]

Out the carb means the valve job or intake valve/pushrod. The crankcase leakage can only be rings. I'd pull that one head and inspect. It may be that the particular cylinder needs the rings to seat and the pushrods are wrong on the one side because that head was cut more (and probably on an angle) during earlier services.

 

[IQ52]

so I did a leak down test on the two cylinders with the lowest compression. on cylinder #2, after pumping it full of air, I smelled fuel and also heard air coming from the carb. Put my hand over it and sure enough, I could feel the air coming out. I only pumped in around 50psi. I then did the same thing to the next cylinder (#4), this time the air was coming from the dip stick. if I'm not mistaken, this means either I need new rings or the cylinder wall is messed up in some form or fashion. Thanks for the help guys.

Umm......did you put each cylinder on top dead center before you set the air to it?

 

[multipleBs]

Either find TDC for each cylinder before testing or remove the pushrods on those cylinders. You need to make both valves are closed. Also, if pushrods and rocker arms remain in place it has to be TDC on the compression stroke not TDC on exhaust. I would do it with the rocker shaft removed, then you're sure.