HELP!!!!!!!! Cylinder head not sealing against cylinders????

[mikemango]

Hi Folks
ive had an ongoing problem with my bus engine, popping and slight backfire at idle.
tried all the suspect issues vacuum leaks etc.
got round to doing a compression test and found that i only have 30psi on no2 cylinder!! :shock:
stripped the heads off to find a gas leak between the head and the cylinder, re-lapped the head and fitted it together but still have the leak?
is there some sort of shimming procedure to cure this or do i need new engine casing or heads possibly?
im a bit stumped as to what to do next?
anybody got any good suggestions?
all the other cylinders are good and giving me 125psi?????? :roll:

Regards
MIke

 

[dustrat]

I had a similar problem a few years ago. First of all check to see if the mating surface of cylinder barrel is OK and is not burnt away. If that is OK the next solution is to get a good machine shop to fly cut the head and supply shims to build it up again. Depending on price it may be a better idea to get either a new or second hand head.
Robert

 

[jonboylaw]

I think that is what he meant by re-lapping the cylinder to head. If the barrel is burnt then it will need fly cutting and shimming or new barrel/s.


Sent from my GX64 SatCom phone using Tapatalk

 

[lhu128l]

There is another "old-Skool" method......

Use a SMALL amount of Valve grinding paste and "Lap" the cylinder to the bore/head.....

I have done it several times when using "Old Parts"

This is virtually impossible to get right . They need to be done individually on something flat ,even they it's difficult to get square ...machining is best

 

[Bay-low71]

Why not try copper head shims, as mentioned not the proper method but if it gets you away to use the rest of the summer (if it's still here) then could then be put on the winter work list. I've got a 0.040" (1mm) set they are a bit thick. Fitting shims will change rocker geometry, but you may get a seal.