nicked a valve seat....

[thinman56]

so, my 1980 head has been back from the machine shop for a while, and i thought i would pop the valves out of it to make sure they did the backcutting and apply some new things i read from these posts on the ports. i was being as careful as i could with the dremel tool and a stone, polishing up some guides, etc, and i got to the 11th port when i nicked the valve seat with the stone on the way out. three or four small scrapes right on the main, 45 degree slope where the valve actually seats, enough to feel with your fingertip. i haven't done anything yet, it occured to me that if i polished up with a bit of emery cloth, i'd probably take the highpoint off but leave the scratch. should i get an old-fashioned lapping stone and give it a few turns? any suggestions?

 

[Anonymous]

tahts one nice ride...

no answer to your question

 

[addo]

I'd name that valve seat "Sunshine"

Seriously, there's unlikely to be material raised. It's often illusory. A picture would be best here. If the scratches are fine in nature, you may be best doing nothing. Otherwise, maybe a little coarse paste to lap it, then some fine.

 

[thinman56]

thanks. i'll try the lapping compound. mostly i felt like an idiot for sticking a whirling stone in my freshly rebuilt head. somewhere there's a line in the sequence that says, 'port and polish before valve job'......

 

[LameHoof65]

Well, when people are honest, most of us have done things like that. If you can feel it with your finger--I would probably try lapping it as well. Oh, and yea---very nice fastback, nice indeed.

 

[MustangSix]

Lapping will get rid of a pretty major nick. And normal use will take care of further seating. Just make sure you have full contact between the valve and seat before operating. Leakage of hot gas can burn a valve pretty quickly.

 

[Anonymous]

thinman56,
You've already gotten the advice I'd give.
Funny thing about advice also.
It usually comes from experience.
It would in my case anyway!
The good part is you are correcting your problem.
Some shops would have said, "hey its a new job, it'll work okay"!
Good luck.
DaveP

 

[Guest]

I would do a regrind and then a re lap. Just to make sure. Compression levels and non burnt valves are pretty important.

Easy for me to say, my dads got a valve grinder, and Ive done like ten thousand grinds on it. I guess its more accesible for me, but I would ask the shop what it might cost....$10? Worth it.

 

[wsa111]

Scott, it happens to the best of us.

Try the valve lapping compound first, if you don't get full contact at the seat, take the head back to the machine shop for just a finish seat on the 45 degree mating surface. If it doesen't lap out please take it back to the shop for a retouch.

If its an exhaust valve seat with a hardened insert, don't even waste your time trying to remove the damage via lapping with valve grinding compound. Take it directly back to the shop to get a professional seat seal. Do it right now & it will prevent a burned valve in the future. William

 

[thinman56]

thanks for all this, men. i lapped the seats, there were two actually, both intakes, and they seem to be okay. you can barely see a couple scratch marks, but cannot feel them with fingertip or fingernail. just have polishing left now, will religiously turn off the machine before extracting the bits....