Head/block tolerances

[Scuddy]

Hi all

Anyone know the allowable head/block tolerances on a 2.4TD? (microns or thou). I've got a new head but want to make sure there's no warping on the block (unlikely I know). Seems like I've also had a pressure leak path under head gasket at cylinder 4 (surface pitting) on block.

Rather than remove the block and skim it, anyone know and allowable depth/width in a pitted surface that the gasket will accomodate?

The only other way I can think to prevent future leak (other than skimming block or replace engine) is gasket paste or head crack sealing compound. I know Holts do a crack seal compound?

Any suggestions or experiences greatly appreciated.

[marky]

STEVO will have the answers you require.

[Scuddy]

Tried STEVO, but got no joy, got the cold shoulder and he thought I had a front as I didn't get the head from him...can see his point!!

No offence was meant to be caused...It'll just have to go back together as is and hope it seals on the gasket OK

[stevo]

tolerance

Your manner didn't help! a flat block is absolutely essential because with the head gasket effectively being a series of steel shims there isn't a lot of 'give'
a normal composite style gasket compresses more and can cope better with slight undulations in the block, we allow no more than 002" ( 2 thou ) variation in the Surf block surface, anything more and we skim it. Hope this helps.
Cheers, Steve.

[Guest]

Also the New headgasket - certainly the non genuine one, comes ready coated with some kind of elastic rubbery stuff which will take up some imperfections. To be honest for me it would depend where the imperfections are, if you have a decent amount of flat metal around anywhere there is combustion pressure, water pressure or oil pressure then you may be OK with bigger imperfections than if there is only a small amount of good surfcae around them if you know what I mean.

Cheers

[jet1749]

As already stated, the mating surfaces have to be as flat as possible, however the machined surfaces on a newly manufactured head and block can look quite rough in texture, and this is intentional in order for the gasket to key to the surfaces. General method/rule of thumb that I have used has been a straight edge or parallel flatness check with feelers indicating bowing of the head to be less than 0.002" for every foot (not surf specific) Another check is to use a machined marking out table (or substantial bit of plate glass, but not domestic glazing) paint a very thin coat of marking blue available from any engineering merchant onto the surface of the table or plate glass. Place the head onto the table or plate glass and rub the head on the table/glass, remove the head and look at the surface. the marking blue will transfer to the high points of the heads surface and leave the low points uncoated. that will give you a quick visual indication of the flatness of the head.