thumper64

I got new valve guides installed in my head and the exhaust valve seats have some pitting. I have done some reading and people say to get the seats cut. I know the old school guys would lap or grind the valves with abrasives to clean up the seats and make the valves seat. But new guys are saying not to lap them, even though it's been done for decades. It "exposes the seats". If recutting valves and seats with other tools is ok, then why is essentially sanding them taboo?

Short version:
Is it ok to lap valves just to clean up some mild pitting and ensure a nice seal?

I have a B18C1 head, if it matters.

infinitypro12

I"m terrible when it comes to engine stuff but I'll take a stab.

From what I could find you should be ok to lap but due to the amount of possibility there is to mess it up and hose your top end, I'd just buy a new head but I don't know what kind of budget your on.

Anon51

assuming you send the head to get cleaned after lapping then lapping is fine depending on how bad the pitting is. also assuming you're valves are newish with no pitting themselves. if you're using pitted valves then you should get the valves and seats grinded instead since most machine shops will match each valve to each seat atleast the machine shop i take mine to anyway.

93h2beg

the only issue i have ever had with lapping valves is the mess. clean the hell out of ur head and ull be fine. I have taken down some bad pitting with course compound, then moved up to fine. it takes a while but compared to a machine shop its basically free!!!! if you have the time try it, do NOT use a drill on the valve it has a chance to get the compound on the valve stem and mess up the guide. slow and steady.
Ive done it and ran many many miles with out an issue.

thumper64

The person saying to get a new head: That's not an option. GSR heads aren't cheap and I'm putting new valves and guides in to freshen it up since I'm rebuilding the motor.

Alright, I just lapped my valves. I sprayed a little oil on the stems, dabbed the compound on the sealing part of the valves, hand spun them, switched to some polishing compound for plastic (it's the consistency of toothpaste) and now they're shiny.

So basically just wash everything, maybe oil it a bit and I'm good to go?