Lapping the coatings off....Q?

n2xlr8n · Post by **n2xlr8n** » Sun Jan 22, 2006 5:33 pm

I've never done this before, so bear with me:

I'm lapping the valves in a DOHC head. I decided at the last minute to try Swaintech's coating on the valves, chambers, and ports. The valve job had already been performed. Swaintech informed me that I would have to lap the valves to remove the coating from the seats and valves.

Q: The coating is roughly the color of the seats / valves. Am I supposed to lap them enough to see a nice "ring" on the seating area, or am I supposed to see 100% metal on both surfaces?

Swaintech was kind of vague, and I wasn't experienced enough in this area to ask the right Qs.

I'm using Permatex #765-2657 valve grinding compound, as I felt the #34A was too coarse.

Thanks for the input.

Fkned · Post by **Fkned** » Sun Jan 22, 2006 8:11 pm

Couldn't you just face the valve slightly and touch the seat w/a stone to accomplish the same thing.

steelcomp · Post by **steelcomp** » Sun Jan 22, 2006 9:29 pm

I think I would call Swaintech and ask more specific questions.

hotrod · Post by **hotrod** » Sun Jan 22, 2006 9:53 pm

You will want good metal to metal contact between the valve and the seat for both a good seal and for thermal control of the valve temp. (lots of heat gets carried through the valve / seat contact to cool the valve)

I would simply take a magic marker and color the edge of the valve and valve seat ( poor mans dykem blue).

Lap until you get a clean full width line on both the valve and seat.

The magic marker line makes it easy to see the true area of contact.

You may need to apply color to the surfaces a couple times as you lap them, to get to the point you have achieved the full contact between surfaces.

Magic markers are very useful for layout and checking contact like this. Everyone should have several in their tool box.

Larry

n2xlr8n · Post by **n2xlr8n** » Sun Jan 22, 2006 11:43 pm

hotrod wrote:You will want good metal to metal contact between the valve and the seat for both a good seal and for thermal control of the valve temp. (lots of heat gets carried through the valve / seat contact to cool the valve)

I would simply take a magic marker and color the edge of the valve and valve seat ( poor mans dykem blue).

Lap until you get a clean full width line on both the valve and seat.

The magic marker line makes it easy to see the true area of contact.

You may need to apply color to the surfaces a couple times as you lap them, to get to the point you have achieved the full contact between surfaces.

Magic markers are very useful for layout and checking contact like this. Everyone should have several in their tool box.

Larry

Thanks, Larry. I had some dykem spray, so I used that; Good idea.

I'm not a machinist, nor do I have a stone for valve seats, so I couldn't use a stone. I think it would've taken off too much material, anyway. My machinist set the valve depth at a point that also set my valve lash on the buckets (save me $$$).

Thanks, everyone.

MadBill · Post by **MadBill** » Mon Jan 23, 2006 10:37 am

We're looking at Swain coating of entire valve heads too, but haven't spoken to Dan yet. My concern with the above suggestion is that just because you have verified good contact over the full width of the seat on both valve and head is no assurance that you have 'broken through' the coating. If you have not, there will presumably be a lack of heat transfer and the possibility of it peeling off in this heavily loaded contact zone...