Teddy952

Before installing the head last night I measured the top of the pistons relative to the top of the sleeve. The pistons are sticking out past the sleeve by .018". My sleeves are o-ringed and I zero'd out the dial gauge to the top of the sleeve not the top of the o-ring in the sleeve. I know the o-rings add some height to the sleeves but I haven't measured how much yet. Should I zero out the gauge on the top of the o-ring or top of the sleeve? All the measurements were taken along the crank's axis.

I believe the widefire head gasket will compress to 0.40" once the head is torqued. That leaves me with .022" difference. I'm worried about the pistons hitting the head. These are Wossner pistons with stock head, rods and stock 2.5 crank. Block is 2.5 with steel 102mm o-ringed sleeves.

thanks!

blown 944

Measure at the sleeve. Wow you are really close. You need to rock the piston to get absolute minimum clearance. I've never ran more than .010 out of the hole with this thick of gasket.

Sounds like too much was taken off the deck surface. If it were me I'd do away with the o rings and use a thick cometic. This of course after measuring a hundred times.

Teddy952

I have no problem using a thicker Cometic gasket but as you stated the o-rings need to be removed. How do I remove the o-rings and do I just install the thicker Cometic gasket over the open groove? Also, how thick should it be?

Tom M'Guinn

Right, officially the stockgasket compressed to 1.1mm or .0433" (though actual measurement vary). I'd agree that you are cutting it too close and should look to make more room via the head gasket. The o-ring does not add meaningful height, as the o-ring just creates a groove in the fire-ring -- see photo below. I'd be hesitant to pull the o-rings and run an MLS over the open o-ring grooves, although I suppose it depends in part on how far out from the inner edge the groove is (i.e. how much sleeve top there is to seal on). If those are steel sleeves you could probably have someone tig weld in the grooves, then machine it all flat (which is likely to take off a few more thousandths). Victor Reinz sells a 1.4mm gasket, which would get you to .037" but that's still a tad tight I'd say-- although plenty of folks would say its fine if you have strong rods and light pistons -- but I don't think the thicker gaskets come in widefire form, which can be important if your o-rings need the extra width to "grip" the gasket. How high does the o-ring sit? If not too high, another option would be to go with a pure copper head gasket -- copper gaskets can be used with o-rings (as long as the o-rings aren't more than say 5 to 10 thousandths above the deck) and can be ordered in various thicknesses.

Teddy952

Hey Tom.
O-ring sits .005" above the sleeve. Instead of finding a thicker, o-ring compatible, head gasket I was thinking of machining the top of the pistons. If I was to shave .010" off the top of each piston that would give me plenty of clearance. The pistons are easier to pop out than screwing around with that o-ring and spending more $$$ purchasing another HG. Any suggestions on machining material from the piston tops?? Belt sander.... hammer and chisel? =D