Surfacing heads for cometic head gaskets-- anything special?

[GN SBS]

I plan on using cometic head gaskets with my rebuilt motor and have read a few posts that suggest that these gaskets like a particularly flat and smooth head and deck surface.

Any comments on the facts behind this? If this is a particular concern, what instructions shall I give my machinist.

Thanks much,
Scott

 

[The Radius Kid]

If you're resurfacing the heads,make them smooth[very little "courderoy",he'll know what I mean].
You biggest concern will be the decks on the block.
They should be smooth with no pitting where the gaskets seal.

 

[GN SBS]

Thanks for the advice on smoothness.

I spoke to an engineer at Cometic this afternoon and they recommend that the surfaces be 50 RA or smoother (in machinist speak), or smooth enough that running your thumbnail along surface does not drag anywhere (in layman's terms). They also suggested that this level of smoothness should appear slightly polished to the eye.

Because of a lack of fibre these gaskets are less forgiving when it comes to filling in any imperfections in the head surface.

thanks!
Scott

 

[chevyII]

Felpro makes a gauge to check surface smothness its very critical in todays aluminum engines.