cylinder compatibity - 3.0 v 3.2, sealing ring
 

Hi,

I'm researching a project and trying to decide whether or not to go the 98mm 3.2SS route or just stick with 95mm cylinders. In searching prior posts, I couldn't find a definitive answer to whether cylinders without the sealing ring (i.e. carrera) could be used with heads that have the ring groove machined in them (i.e. SC). Can the SC heads be used as-is on a barrel without the ring groove? Would a sealing ring (gasket) be used or not? Or, would the heads need to be machined to a flat sealing surface?

Sorry if this has been answered elsewhere, but not being able to search on 'SC' has it's limitations!

Thanks!
Tom

P.S. - The car is a '78 US-spec targa. Parts acquired so far are SSI's, web cam 20-21's, and heater backdate parts. I would like more compression and maybe more displacement - that's the last major decision to make.

I didn't think 3.0 heads had grooves in them - just the cylinders.
(If they do have grooves in the head this is going to be embarassing 'cause I've built a couple of SC motors...)
-Chris

The heads don't have grooves, only the tops of the cylinders. I see no reason you couldn't use them interchangeably.

You can't interchange pistons though. The wrist pins are different size and location.

-Andy

Mahle Motorsport uses the same 98mm cylinder whether a piston with a 22mm pin for an SC or early 930 or a piston with a 23mm pin for a Carrera or later 930 is stuffed inside. No headgasket is used. The only mod you will need to do (or your machine shop) is a small chamfer on the heads to match the larger bore.:)

Ralph

Thanks! That makes the decision to go big bore that much easier :)

i would recommend flycutting the sealing surface of the 3.0 heads just enough to get a true, clean sealing surface. they are usually marked up from corrosion, running with a broken head stud or just 30 years of thermal expansion. up to 0.25mm can be taken off, and compensated for with an extra cylinder base shim. don't forget to take the same amount off the outer face of the head so it doesn't contact the outer machined step on the cylinder.