bad compression test

[jeremy_gass]

just got my 71510 sr20det retuned... and something went bad... oil filling my catch can yes its set up right(never had problems with it before)

bad compression test
cold
150
150
150
80

-tried it again with oil in cylinders and didn't do much for them...
-so i hope its in the valve or HG not the bottom end...
-car runs fine.. not sure how it runs as well as it does
-took valve cover off seems to look ok didn't see anything standing out as far as valves look...
-car does not smoke
-so my boost is getting into my oil and pumping out into my catch can....
-i seen someone had a head gasket go and it leaving compression and going in oil passages can that be it?
-coolant looks ok and oil looks ok...


what should i test next?

[Hoffman5982]

Head gasket will usually result in 2 bad cylinders. If it didn't jump up with the wet test, your rings might be fine. When mine went I got like 60 on the dry test, put a cap full of oil and it jumped to 140-160. It could be valve seals. Best bet is to get a leakdown test done.

[compactfean]

Id say needs a valve job but hoffman is right, don't assume anything until a leak down is done and you're sure what the problem is.

[jeremy_gass]

so how do i tell from the leak down test.. what will i see that tells me head or ring....

[jeremy_gass]

had a fancy camera in the plug hole looks like ring lands broke maybe a hole or something else in it too... guess im ordering a new piston and set of rings.... it didn't get hot think i will still get head checked but im wondering what HG should i get? whats the stock hg thickness?

[Hoffman5982]

Cometic is a decent HG and cost effective. I went with a 86mm x .045" which is slightly thicker (1.1mm) than stock and had no issues from it. It's recommended to have your head and block decked when going to a metal headgasket, and if you can I suggest doing it, but the Cometic gaskets have a rubber-like layer to aid in a good seal. A lot of people also suggest spraying the gasket with copper spray, but the one time I did on my old Cometic was the only time it failed on me.

[Hoffman5982]

And, of course, go ahead and grab some ARP head studs. You don't want to reuse the oem ones, they're designed to stretch.