compression

[xsnrg55]

My 1969 Mini Cooper 998 had great compression and all of a sudden, drive to/from 50th Mini meet. maybe 80 miles I could tell the pull was dropping on the way home, latest compression check shows 125 to 130psi across and jumps to 150psi with a spoon of oil. any magic trick here or am I facing a rebuild?

[Cheleker]

What were the previous "great compression" figures?

[xsnrg55]

well thats a good question, I did not take a compression check after replacing a highly modified head with a unused stock head. so i really don't have anything to compare with, other than I've lost a lot of pull and now have blue smoke.

[Jerry]

I don't know what the compression figures would be in a healthy 998 but a bump in compression when oil is added to the cylinder usually points toward worn piston rings rather than worn valves. It could be that the engine needs a tune up and that the the source of the blue smoke is from worn valve guide seals. Does it smoke all of the time, on deceleration or on start up?

[xsnrg55]

It blows a plume of smoke when revved up, otherwise no smoke. should l remove the head and have valve guides and seals replace.

[Jerry]

You mentioned that it was an unused stock head which tells me that the valve guides/valve stems shouldn't be worn. I'd pull the head and change the valve guide seals. Replacement Viton guide seals are supposed the most effective in stopping smoking engines, LJQ101160 is the part number, available from Mini Mania or Seven Enterprises. Not sure what type of valve guide that you have installed in your cylinder head, so these seals might not be correct for your application. From what I've read, the valve guides should have a groove cut into them to accept this type of seal. Call and talk to the nice folks at either MM or Seven.

[mascher]

Try a leak down test before you tear anything apart. The club has the tester although you may want an experienced hand to determine the results.

Kelley

[xsnrg55]

Leak down sounds like a good idea. I have a friend that
suggested the same thing and will do it. thankyou

[Jerry]

Keep us in the loop.

[xsnrg55]

i will thanks