Piston rings. Advice apreciated

[Vic Rattlehead]

Afternoon all.

Just done a compression test on my 91 Turbo with the following results.

1 = 140
2 = 120
3 = 145
4 = 142

I had the head rebuilt last year whilst having the head gasket replaced so I'm assuming that valves aren't the issue here. Also after squirting some oil into number 2 the compression went up to around 135. Which is leading me to worn rings on number 2. I will be getting a leak down test done to confirm, but was just wondering...

1- Is it a massive undertaking to replace the rings on these cars? As the car is my daily drive. And just trying to get an idea of how much it might cost at the place that does my major work.

2- Other than valves, rings and head gasket could there be another reason for my shoddy compression on number 2? Cracked block and warped head spring to mind.

There's no blue smoke when driven and the spark plug from number 2 looked perfect and not oil fouled.

Thanks in advance everyone.

 

[sawood12]

What is considered acceptable values in the manual? for all you know, although cylinder 2 might be lower than the others 120 might be well within acceptable limits and good for another 100k miles. If you've got no blue smoke or other symptoms then why change it if it aint broke?

 

[Vic Rattlehead]

Not sure on what is considered an acceptable figure. I'll have to check that but it was the difference in figures that set alarm bells off.

I've always read that a difference of over 10% between cylinders is bad.

 

[sawood12]

You're probably right about the relative values. If you've had the cyl head gasket fitted recently then hopefully it is a sealing issue with the gasket and therefore a cheaper fix. I've never heard about problems with cyl 2 - it is usually cyl 4 that has issues if any of them is going to.

 

[Frenchy]

Drive OK ? then leave it as Scott said any issues re usually with No 4.

 

[Vic Rattlehead]

Seems to drive fine. Although it seems to feel like it's not quite as punchy when boost comes in. But that could be that the old arse dyno has gotten accustomed to it after 2 years of ownership.

Decided not to jump the gun. I'll keep my eye on it. If it suddenly deteriorates and oil usage soars then I'll get it checked out.

Scott, good call on sealing issues. I'll look further into that!

Cheers