[waid786]

After spending half hour trying lap my pitted exhaust valve, I realized it was a hopeless cause. This is my 96 Explorer exhaust valve with 250,000 miles and is little pitted.

Since I had nothing to lose, I chucked the valve tip (same #4 exhaust valve) on a cordless drill and after only 1 minute of turning clockwise and counter-clockwise while lifting the valve off the seat after five seconds and pulling on the valve, the valve lapped perfectly. The hand tool is worthless.

Waid

 

[waid786]

After lapping with a drill !!!

As you can see, the valve and valve seat looks good and mineral spirit is not leaking out. I was told it would never seat!

I am going to lap it again for another couple of minute to ensure that the valve/seat has even bigger contact surface.

Waid

 

[FEandGoingBroke]

The larger contact surface will avail you but little and it will be more prone to getting things stuck in them.

I also use the drill to lap my valves when the lapping is just to clean things up.