Valve Lapping

[bpcatdog]

I have some 40 x 35 heads that I bought new and they have roughly 500 miles through them. I've heard some people state that it's a good idea to lap the valves to obtain a good mating surface with the seats. My question is, if I want to lap the valves is it necessary to get a valve job done first or can just go ahead get some clover compound and lap away? Also what grit compound should I use?

Excuse the trivial questions, but I just want to do things right.

Louie

[sparkmaster1]

It's not a bad idea. Use some clover medium or fine grit. It also gives you a good idea where the valve is actually riding on the seat. Finer the better, you want a smooth surface on the valve and seat. Tim

[bpcatdog]

Tim,

Thanks for the advise. I guess it's time to dig out the lapping stick. I know it's around here somewhere in a box. Hopefully the suction cups aren't dry rotted. NAPA should have some fine grit compound.

Louie

[sparkmaster1]

I just use a piece of Fuel Hose on the Stem. Tim

[rui]

I have a way with lapping the valves. Using a small drilling machine with variable speed and reverse function I attach a piece of fuel hose clamped to a drill bit and insert the bit into the drill. I then fit the other end of the hose to the stem of the valve and clamp it, the hose is about 10cm long, if it is too long it twists, this gets the valves lapped in double quick time. Make sure the head is tight on the vice with valve face showing up the drill works from the bottom. The stems mus be lubed with Q20 or other.
Once all is fitted and lapping compound has been placed use the reverse function of the drill to do the job.