Polishing of valve shims for a Fiat twin-cam engine

[Stoatgobbler]

Hi there, I'm a newbie on this site with a thirst for knowledge.

I fitted a Fiat twin-cam engine into my Morgan circa 10-12 years ago and have been shimming it by swapping shims or getting a local engineer friend to re-size existing shims, in all cases the shims I've fitted to my engine have their top surfaces (the side the cam rubs on) polished by the cam action.

Unfortunately my engineer friend no longer has the surface grinding equipment and I need a couple of shims which I don't have and so I've bought a couple of the right size from a company online. These are new shims and have a dull, I presume rust preventative, finish on both sides.

My question is:

A) should I fit these shims as is and lube well with engine oil before running the engine?
B) should I fit the shims as is and lube with moly grease and keep the engine revs up as in fitting a new cam / shim.
c) should I polish the top side of the shim and then fit it and then follow A) above?

Apologies if this seems a stupid question but I've been agonising over it for a week.

Stoat

[stevieturbo]

I can see little reason why you'd need to do anything other than fit them, and perhaps lube with a little oil, or whatever you feel is needed.

It would be very odd to have to perform any type of manual finishing on them before use.

[Evoluzione]

^^ What he says: Answer A.

[DVandrews]

I've used hardened shims on hundreds of engines, they are normally case or through hardened which endows them with a dull grey patina. Unless I need to adjust the thickness they go in as they are with a light coating of oil. Over time they will lightly polish due to interaction with other surfaces. That is perfectly normal.

If I have to adjust the thickness they go in with a fine ground finish lightly oiled, again extended interaction will lightly polish the surfaces.

Dave

Edited by DVandrews on Friday 5th May 06:39

[Stoatgobbler]

Thanks folks, I've fitted them as they are.

Stoat

[GTVOX]

DVandrews said:

I've used hardened shims on hundreds of engines, they are normally case or through hardened which endows them with a dull grey patina. Unless I need to adjust the thickness they go in as they are with a light coating of oil. Over time they will lightly polish due to interaction with other surfaces. That is perfectly normal.

If I have to adjust the thickness they go in with a fine ground finish lightly oiled, again extended interaction will lightly polish the surfaces.

Dave

Edited by DVandrews on Friday 5th May 06:39