Compression Test problem

[Racingrob]

I'm trying to perform a compression test on my 2003 Cobra, but I can't get my compression gauge to thread into the spark plug hole. It seems like there is a shoulder preventing the threads on the gauge from reaching the threads in the head. I've bought two different compression testers and neither with work. Am I missing something? Is there a special adapter for these motors? Thanks

 

[hotcobra03]

I got basic harbor freight. No issues

 

[Racingrob]

The one I got from harbor freight did not work! I borrowed my buddy's tool from Cornwell and it did the job. Results were bad though...compression is 90 psi in cylinder 6.

 

[hotcobra03]

The one I got from harbor freight did not work! I borrowed my buddy's tool from Cornwell and it did the job. Results were bad though...compression is 90 psi in cylinder 6.

Ouch...that was same as 2 heads for me..

But I had 0..

 

[Racingrob]

My results were:

1: 175 psi
2: 164 psi
3: 160 psi
4: 167 psi
5: 132 psi
6: 90 psi
7: 155 psi
8: 175 psi

I then put a tablespoon of oil in cylinder 6 and repeated the test. Cylinder 6 then jumped to 110 psi. That leads me to believe it has bad piston rings. But seeing the bad compression in the cylinders around it leads me to believe it has a bad head gasket.

Any input on this is welcome! It is an 03 Cobra without the head cooling mod. I literally bought this car from High End Auto in Appomattox Virginia on Saturday and the misfire code appeared on Sunday.

Car has 52k miles and is stock besides JLT intake and UPR offroad X welded to a Borla Stinger Catback. First owner was elderly so I wouldn't have expected many top speed runs. Confused as to why this motor would have this issue considering its history and condition...

 

[hotcobra03]

I take it back

 

[hotcobra03]

Mine last month..installed new plugs had to look..been 200k on plugs..

Car is at 414,000 now

 

[speedoflife]

I literally bought this car from High End Auto in Appomattox Virginia on Saturday and the misfire code appeared on Sunday.

Car has 52k miles and is stock besides JLT intake and UPR offroad X welded to a Borla Stinger Catback. First owner was elderly so I wouldn't have expected many top speed runs. Confused as to why this motor would have this issue considering its history and condition...

@Corbic
Yeah... High End doesn't exactly have a stellar reputation here.

Sorry to hear about your engine troubles. A tear down is necessary no matter what at this point.

 

[Corbic]

@Corbic
Yeah... High End doesn't exactly have a stellar reputation here.

Sorry to hear about your engine troubles. A tear down is necessary no matter what at this point.

 

[hotcobra03]

Maybe you let cobra Bob add this to what to look for when buying...

It's always been highly suggested to do compression test..

Was the engine hot or cold..

This could just be a head issue..

I had the 2nd head repaired which lasted a 100k before cracking..

Cracked was cyl 7..compression was 140