Question on sealing heads / cylinders, Advice needed on lapping cyls to head Options

[Joe Owensby]

I have done a search here, and have found some info, but not all I needed. Most say to just lap the cylinders to the heads. I have a 2056 kit from Raby, with all new parts. How precise should the interface of the head to the cylinder be? My new heads have small machining grooves on the area where the head will mate. Small, but can be felt with a fingernail. The cylinders also have small machining grooves fromt he lathe cutting. I have lapped the cylinder to the head on one cylinder. I have done this to the point of getting a uniform type of mating all around the surface. However, this is to the point that the small grooves are still there, ie it is not a completely flat polished surface. I am guessint the grooves are about 3 thousandths deep or so.

I was wondering if the grooves could actually help sealing, as I have seen a lot of gaskets, etc. that have circumferentially grooved or ribbed surfaces to allow a higher unit contact pressure around the full surface, and maybe allow for accomodating slight imperfections in geometry. I also saw on Jake's website where someone, I think Len Hoffman, said there was a taper machined into the cylinder mating surface, about 0.0015 or so. On this site, there was a mention by Jake to first lap the cylinder on a glass pane, and then lap the cylinder to the head.

Any clarification you can give to this will be greatly appreciated. Thanks, Joe O.