series 2 jota

mines not, its flush with the head face.....

it must have been skimmed.

do i need to have the head machined to re-introduce the recess in the skull?

stephen
 
STEPHEN said:
Looking at the liners in the barrel casting, the top of the liners are stepped - the outer diameter of the liner sits just below the gasket face, the inner diameter or the bore, sticks up and is raised above the gasket face by 2.3mm.  This part obviously touches the metal skull in the head.
If i pop the head gasket over the liner it sits over the raised part of the liner, but the gasket is only about 1mm thick, so the gasket cannot be compressed at all.
Click to expand...

The liner should NOT come in contact with the head.  This will not allow the gasket to do its job.

If the liner does contact the head, the head has most probably been skimmed too far.  If spigot height is reduced to fit, the pistons will protrude and can contact the head...

Found exactly this scenario in a 750 engine a couple of weeks ago, the head had been skimmed to the extent that the pistons clouted the squish band of the combustion chamber.  Lucky we got some NOS heads to help the guy. :D

If your liner spigot is 2.3mm, the recess in the head must be at least 1.5mm.  The stock 1mm gasket does not compress much at all, this will give a little clearance between liner and head and provides a good gasket seal.

piet
 
thanks, i need to check the squish clearence and the make sure the valves dont hit the piston.

no such thing as an easy problem...

what about a special thick head gasket?
 
Oops, simultaeneous posting...

If you have the head machined to suit, chances are you won't be too happy with it.  CR will probably be way too high for road use, even with flat-topped pistons, might be ok for track use though if running on dope.

Alternatively, you can use it with 80mm or larger bores and flat-topped pistons.  These cylinders no longer have the spigot and the head gasket gives ample clearance to the head.  CR will still be quite high, but should be within a usable range. 

You'll then find the cam chain is a bit long at one end... :D

piet
 
Thicker gasket may cure your woes.  Don't know where you're going to get it.  Perhaps a solid copper item?  Possibly the only affordable option.

piet
 
I have 1.5mm custom made head gaskets here
am ordering more today but their bore size is 82.0mm, will not work on the smaller capacity engines

check the overall thickness of your head, should be 94.0mm if it has not been machined

 
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