Lap Cylinder Heads

I had time this weekend for one more project - lapping the cylinder heads. There is no "head gasket" used between the cylinders and the heads. It is just straight metal-to-metal contact to tightly seal the combustion chamber. To make sure that my cylinders will be seating properly, I decided to "lap" or grind the the heads in place. This is a gentle task where we'll take valve grinding compound (fine silicon-carbide grit in either a paste or water solution) and first apply it to the contact area:

Valve lapping compound on a Porsche 914 cylinder head


Put the cylinder in place, and with a rotating action, allow cylinder to "grind" against the head. I decided to only oscillate the cylinder back and forth a little bit - to keep its orientation as close to the installed orientation as possible. I'd say that my rotation was only about 30 degrees.


After a minute or two of this, I inspected my progress and was pleased to see that there were no "high" or "low" spots (spots where the cylinder wasn't touching the head - which would have been visible because there would still be a shiny spot... not the dull gray of the lapping.)

Inspecting the cylinder lapping of a Porsche 914 engine


And here's a shot of one head done (and cleaned) on the left, compared to the other head:

Lapped cylinder head for a Porsche 914 engine


(Because my heads are new, this step probably wasn't required... but I think this would be a must if reusing heads, in case they have warped or distorted over time.)

I also had a chance to clean up more miscellaneous parts:

Misc parts for a Porsche 914 engine

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All pictures and text copyright 2008