Extra Steps for Machined heads?

[smestas]

I just had my '78SC heads redone and they had to be surfaced .25mm to get them right. I just ordered the larger cylinder sealing ring (copper) which is .50mm from .25mm to make up for the material removed from the heads.

My question is there any extra steps or procedures that I need to do since these heads have been machined besides puting in the thicker sealing ring?

[echrisconnor]

I don't know whether you consider this an "extra" procedure or not, but I'd certainly measure my piston to valve clearance carefully.

You may not need those extra spacers if your deck height is generous. That material cut off could be good for a small compression bump.

[smestas]

Originally posted by echrisconnor
That material cut off could be good for a small compression bump.

Has anyone else here done this for a bump? If so what kind of increse should I expect to see?

[echrisconnor]

Search on "fly cutting" or "compression bump/raise/increase" you'll find a few threads on it. It's also mentioned in Wayne's book. Not sure what the increase will translate into CR or HP, but it will be a small increase.

With your low CR P&C's I doubt it'd bump more than a quarter point.

[Wayne 962]

It's assumed that most heads need machining, so I wouldn't really call it an *extra* step...

-Wayne

[kstylianos]

Assuming stock compression ratio of 8.5:1. Milling .25mm off the heads will bump CR up to ~8.85:1.

Check your deck heights and your piston to valve clearance to be certian you can do without the extra .25mm shim. Since the early SC's pistom dome volume was a little less than the later years, this is probably doable. Check anway.