skimmed head advice

[Skallywag]

Hi everyone.
Just had my S30 motor back from the local engineering shop for a general once over. Thought it a good idea since the last time it turned over was back in September 1986. They informed me they had taken five thou off the head (against my instruction to leave it alone since it was nice and flat) and I'm now wondering what the hell to do.
Will it be ok to leave it as is and run it? since the engine turns over freely by hand with no knocks or clicks. Of course metal expands a tad when hot, so I'm in a bit of a dilemma.
If anyone has experience regards skimmed heads and what to do, that would be great. The last thing I want to do is put it back in the car and have a catastrophe with the motor.

Thanks in advance
Rob

 

[jonbills]

0.005" is ~0.13mm - I think it'll add up to about 0.75cc.
Unless it was already heavily skimmed or it has a high lift cam or other exotic modification affecting compression or valve/head interference, it'll be fine.

 

[richiep]

As Jon says, don’t worry about it; it’s a minuscule amount that just serves to clean the head face and will not have a practical effect, assuming the head hasn’t had great reams taken off previously and is running sky-high compression.

Head skimming for performance and compression raising really means, with these heads, taking amounts off in the 1mm+ range. That’s when you need to take other actions (cam tower shimming, different gasket thicknesses, valve reliefs in pistons, etc.).

For comparison, my s30 Fairlady Z runs with an N42 head with 1.8mm skimmed off and 11.3:1 compression with a standard head gasket. Cam towers shimmed, eyebrows in pistons, etc.

 

[Bazzateer]

As the others have said, nothing to worry about really. 40 thou is about 1mm so 5 thou is nothing.

 

[Skallywag]

Thanks for the info regards what to do with the engine guys. The car was four years old when I bought it, so I know it hasn't had any previous work done to the engine.
As I'm taking my time with the rebuild it would be tragic to fail for lack of S30 rebuild experience.
Thanks again and hopefully I'll be able to post some up to date photos of the project as it finally comes together at long last. (only taken six years so far, so about time it was finished)