why do machine work on head?

the local shop says that just to replace the head gasket, it requires they send the cylnder head off to a machine shop for work. i know of this being needed if the gasket blows & possible overheating damage, but why if wanting to place a thinner material? no engine problems at all, but shop wants to do this extra $500 job. plan was to increase the compression ratio, just a little.

They just want check it for warpage to cover their asses. If its warped and they dont send it to the machine shop to be checked and milled if needed, the head will leak and youll be pissed.

$500 is rape though......

You would be best off to do it yourself. Take the head off and clean all gasket material from head and block. To check for warpage, lay a straight edge on end crossways on the head and check with feeler gauge. Do this on the other cross and then straight across. Also do the same to your block deck while its open. I dont know what the Honda tolerances are but they will be easily found in a Helms (mines at home).

is it 500 for the whole job? that's steep. but ok for a head gasket replacement from a shop. do it yourself and save $400. if you want to mill the head know that it is irreversable. do your math on how it will change your static compression ratio and piston to valve clearance. if it really needs it mill as little as possible unless you know what you are doing. shops shouldn't charge too much to mill your head. around $40 i think. and get a copper head gasket if you plan on big hp. you can also get a thinner head gasket for higher compression too, and you can always change it later.