lapping in valves

[oldlineman 1,481]

I am somewhat mechanical, but could someone explain what is involved when one says he/she is lapping in the valves in a tractor motor? Thank you as always, never too old to learn.  Bob 

Edited January 24, 2014 by oldlineman

[Jrblanke 857]

Not sure exactly, but it sounds like something you could look up on Youtube.

[rmaynard 15,417]

Lapping valves is the process whereby you create a matching surface between the valves and the valve seats. As the engine runs, the surfaces of the valves and the seats will wear. Sometimes it's bad enough that both the valves and the seat need to be ground. This is done at the machine shop unless you have the equipment, and if you did, you probably wouldn't be asking this question. Sometimes the valves need to be replaced. However, if your situation is such that all you need to do is "lap" them, that is done with a lapping tool:

 

 

and valve lapping or grinding compound. The process is done by attaching the suction cup to the top of the valve, applying a small amount of compound to the underside of the valve, applying a small downward pressure while spinning the lapping tool between your hands.

 

 

As Jrblanke said above, it is well covered with many videos on YouTube.

 

A finished lapped valve will look similar to this.

 

 

 

[shallowwatersailor 3,213]

Brings back memories of learning to lap Detroit Diesel 6-71 injectors and valves in Engineman "A" school.

[oldlineman 1,481]

Thanks Bob that is about what I had in mind but thought you needed some sort of mechanical equipment, a simple peace of wood with a suction cup on it is very basic and simple. Great pictures and instruction, after that I think I could do it. Thanks again!  Bob   

[rmaynard 15,417]

By the way, I have a thread on lapping that I just recently did. My problem was that the suction cup just would not stick to the exhaust valve no matter what I did. You can read about all the solutions that were suggested and how I finally solved my issue.

 

[honestcharlie56 1]

it never hurts to use lapping compound too.....i believe oreilly's sells it.

[Stormin 9,981]

  I use the lapping stick method also. The only thing not mentioned that I also do, is when I build the head back up, I fill the ports with petrol. If no dampness shows past the valve head, you've got a perfect seal.