Head cylinder mating surfaces

quint22cp · quint22cp's Garage

I'm about half way through a rebuild of my 3.2 to 3.5 conversion.

I had the heads bead blasted to clean all the crud off and they now look great.

My question is the mating surface between the head and the cylinder has no gasket, I don't understand how this works but Porsche made it this way. When I got my heads back the head face now has a matte finish from the bead blasting, is this OK to seal properly or should these be skimmed to a nice shiny finish like this one posted by Cgarr ??

cgarr · cgarr's Garage

Bead blasting will not change the dimension and is fine, I only cut them if there is bad pitting that needs to be cleaned up, The Cylinder does have a slight bevel, I think its about .002 runout to the outside which I think helps seal the surface, You do not want your cylinder top dead flat.. This is as I understand it.

Ken911 · 02-08-2007, 03:50 PM

Some of the people recomend lapping them in together.

MBEngineering · 02-10-2007, 01:22 AM

HI quint22cp lap the heads to the cylinders with fine lapping paste, like you would the valves and with a good light check the surface is matt all the way round on the head and the cylinder, then wash and check with a good cleaner, brake cleaner both dry and re check the surface on both, as for the 0.002 run out to the out side , this was on the 3.2 cylinder only.

regards mike