piston rings

[dave friday]

Morning all, yes i might need some piston rings [compression reading 370 on all 4 cylinders] thing is its been bored 0.60 over size but i did'nt check what the bore size is 77.8? i won't know what the size is untill i take the head off,so...
What suppliers have you lot used?
Ta.

[kevtherev]

The cylinder would have been bored to a specified oversize (1st, 2nd etc) what oversize this is determines the stuff you get from VW

[dave friday]

Ta Kev,but..the starting point can be 76.48 or76.49 or76.50[standard]so 0.60 could be 77.08,77.09,78.00 so?
And i had it bored in Spain so anything is possible

[California Dreamin]

All a bit confusing! oversize means the bores get bigger not smaller and 370 what? Diesel or petrol?
Machine shops normally work to standard oversizes ie: in 0.5mm increments
The only way you are going to know what rings to fit (if it is actually rings) is to strip and measure the bores.
And
Checking the compressions dry and then wet can help determine whether this is rings or something else (valve seats or cracks in the cyclinder head for instance)

Martin

[dave friday]

Well i had a look at the box that the pistons came in [77.48mm] and its a jx engine[diesel 1588cc]so 370 psi is 35 psi below the 405psi minimum.
I've found "Gunzel"and "Awengineering" who both do rings..
As its using oil i recon its the rings.
And as you've noticed i made a mistake with the standard piston sizes,should be 76.48,76.49.,76.50 .
I've read that putting oil into Diesel engines could bugger the compression gauge,if the oil tries to burn?

[California Dreamin]

I've read that putting oil into Diesel engines could bugger the compression gauge,if the oil tries to burn?

It is a posibility ^^^^^

As for the reasons for using oil....you could be right about the rings but you need to ask yourself why the re-bore and existing rings are not sealing.
The engine needs striping and everything needs carefully examining and measuring.

Martin

[jamesc76]

could be as simple as the rings put in line and not 12,6 etc etc

[dave friday]

The re-bore etc was done 40000miles ago and 4years ago,i did a compression check 2years ago[450psi]
I think that the rings aren't very good quality,i did all the fitting and the ring gaps were correct and spaced 120deg apart.

[California Dreamin]

And the new pistons?
There isn't alot more to add without actually having the thing stripped.

Martin

[dave friday]

I think the pistons are ok[they are a well known make].
The reason for the pre-amble is because im in the mountains of Spain and far from main dealers and machine shops.
So...before pulling it apart im making a list. things i can replace later;
head gasket n bolts valve stem oil seals
cylinder hone
big end bolts n shells
piston rings