i got my 3k engine and i got a 4k head I'm trying to do a head and gasget over the weekend with out taking time off work am i right to say the 4k head is a de compression on a 3k-c engine ?

Correct

how much do i need to take off to get it to 3k-c 8.5-1 compression

and is it still to buy 3k head gasget?

3k/4k/5k headgaskets are the same so i'd presume so.

Best measure it. It may have had some already taken off in a previous recondition.

5K isn't the same, different bore size.

how much do i take off the 4k head to match the compression

You would have to cc the head, measure piston height at TDC and figure out the the thickness of your headgasket (after it is compressed) to work it out properly. Even after all that, figuring out how much to take off the head for desired CR would be a bit of a guess.

 

If I were in your position, provided the head you are using hasn't been shaved before, I'd take about a millimetre off - it might bump you up around 9:1 but that won't be a problem. You sure as shit won't have any problems with valve clearance untill about the 4mm mark, and a little extra compression on a tired old 3k won't do no harm.

well its a the work shop atm but getting it shaven flat then taking how ever much off was guna get 5thou off

5thou, assuming you're talking inches, is bugger all.

 

1mm is roughly 40thou

They took off 8 thou just to get it flat and heres a pic

Needs to know how much needs to be taken off

Cylinder head

That looks like it came up nice!!

 

I've just thrown my digital verniers over both my spare 4k head and the corroded 3k bigport head I have lying around. The 4k head is 3.1mm or .122"

taller than the 3k one. If that helps?

That's only a guess as I don't know what's been taken off both. But it's a start atleast. Your still going to have to cc it though to make sure.

Judging by the spark plug holes it's had a decent ammount taken off it, I reckon that'll do you nicely.