TheSamba.com :: View topic - Lapping Valves - Compound leaving heavy scratches

Sat May 30, 2009 9:52 am

I'm trying to lap the valves into the seats on my heads and the Permatex "valve grinding compound" I got at the autoparts store is leaving scratch marks behind. It seems to have too coarse grit.

That's not good is it?

Should I seat them with something this coarse and then follow up with successively finer grits of something? And what would that be?

The heads had a valve job about 5,000 miles ago, but I have the engine torn down for other reasons and just wanted to touch up the mating surfaces. I found some pitting on a couple of the stem ends, so I'm replacing the exhaust valves with new ones (I couldn't find a shop in the neighborhood that could reface the ends on short notice). So I want to at least lap in the new exhaust valves to their seats.

This is actually an old intake valve I'm using on a junk head to test the system before attempting to do the good heads.

Sat May 30, 2009 10:18 am

That's how it's supposed to look part way through, keep going so the compound breaks down and becomes finer. Towards the end don't lift the valve, just keep working the compund that's under it.

Sat May 30, 2009 11:02 am

the cans I buy have course grit on one side and fine grit on the other to finish cut the lapping. That looks like just course grit.

Sat May 30, 2009 11:48 am

Cans??? Could you provide any more details please. The manufacturer? or maybe the store where you got it?

BTW. I'm in the western suburbs of Chicago. If anyone knows of a shop that has a valve grinding setup ... Would really appreciate some help.

I know of only one shop that will work on VW heads. APEX in Bensenville.

Sat May 30, 2009 11:51 am

http://www.newmantools.com/clover.htm
http://www.cylinderheadsupply.com/clovercompound.html

Sat May 30, 2009 12:01 pm

The Permatex Data sheet on their web site seems to confirm the theory that it will gradually slosh out the coarser bits of grit if I continue to work the tool, and eventually hone more finely.

http://www.permatex.com/documents/tds/Automotive/80036.pdf

Note that Permatex Item No. 80036 / Part No. 34A is also available as 80037 (34B), the difference being simply the size of the container.

Sat May 30, 2009 12:25 pm

use the clover. One side is coarse. You lap until it it even, then the fine side cleans it up. Use a rubber hose slid over the valve stem and your hands rubbing against each other to spin the valve back and forth. Every few seconds lift the valve off the seat and move it a bit of a turn.

Try not to wear the valve seats down to where they are wide like your photo shows you are doing. The wider they are the easier it is for carbon to build up under them. All you want to do is clean up where they seat to an even color which shows they are seating all the way around. Also if there is a lot of rocking because of valve guide wear, that will cause it to be really wide too. When you are done put some stoddard solvent in the chamber on the piston side and see if it leaks out. It should not.