Valve Lapping Question

[3Deuces]

Is it necessary to use a course and fine compound? I just did my first valve with the standard permatex stuff. Got a matte finish on the valve and seat. Also did the dykem check but with a sharpie, and that look good too. Will a courser finish be more suceptible to pitting later on?

 

[5twins]

Coarse then fine is the usual routine. The fine does very little cutting and so it's difficult to get all the pits out and get a complete seal. I don't know what grade that Permatex stuff is. Best way to test for leaks is with liquid and compressed air. Turn the head upside down so the combustion chambers face up, install some old spark plugs, and fill each combustion chamber with solvent (I use kerosene) until the valve faces are covered. Blow compressed air in both the intake and exhaust ports and watch for streams of air bubbles emanating from around the edge of the valves where they contact the seat.

 

[3Deuces]

Thanks for the reply. I guess I'll just lap em all then do a leak test.

 

[1974jh5]

On everything I've ever done, I've used coarse for getting rid of pits etc then follow with fine to get the even matte gray finish. I've also done the 'solvent test'; clean the valve and its seat really well, stick the valve back in and hold it tight with your thumb. Then spray carb cleaner or brake cleaner into the port and watch for anything coming out around the valve.

 

[3Deuces]

Where do you find the different lapping compounds?

 

[5twins]

Look for a duplex container that contains both coarse and fine. I got mine years ago at one of the local auto parts stores. Clover is the main brand but many put their label on it. Mine is labeled CTA but it's probably Clover .....

http://www.cylinderheadsupply.com/clovercompound1.html

 

[1974jh5]

Yeah, mine is Clover and I've had it for probably 15 years now. Still works great. Still have a lot left, even after numerous MG/Triumph/etc heads along with bikes.