Used plumbers putty to enhance grip of valve lapper

Not sure if this is an already known method but I successfully used plumbers putty to enhance the grip of a valve lapper's suction cup. I first struggled with losing grip all the time on the exhaust side cause the valves are smaller in diameter. The intake side was no problem. Then I realized that some playdough-like semi adhesive substance could help and reached into my plumbers supply box for some plumbers putty. I took a marble sized pinch of that stuff onto the suction cup and it would hold it really well, almost never losing grip.

A hack in case you have to endure the nuisance of working that tool.

 

Last time we did this to my son's hot-rod Mustang (4.6 block) I took a piece of fuel line, inserted a valve into its correct location, and then forced the fuel line tubing over the stem-end. Now I could work from that side, keeping pressure by pulling on the tubing. Worked perfectly. If you get oil into the tubing, you might want to add a clamp to keep it from slipping off the valve stem. You can lap as long as you want. We even used a 1/2" drill (so that we had ultra-low speeds to save wear and tear on fingers... Just find something you can chuck in the drill that will barely fit into the tubing. Right size drill bit will do the job. A clamp will keep that end from spinning in the tubing.

 

i tried the exact same approach but what i didn't like is that the drill was spinning it only in one direction (OK, you can switch directions but not as rapidly as is needed to get a good grind). and i wasn't getting good results. a couple of valves i tried doing this way ended up leaking and i had to redo them manually. but the putty (or i guess chewing gum) does help the grip a lot