1914 Valve Lapping

E

Ed in Maine

Well-known member
Today the parts arrived to refurbish the valves. I got some fine lapping compound and the lapping tool. I had no trouble removing the valves one at a time to be sure I don't mix them up. Using the lapping compound I find that some valves do have a bright ring around the valve seat and other valves have just a smooth grey, colored seat. I would have thought that after using the lapping compound, the valve seats would have gotten bright and shinny. I know I don't want to over due the lapping and change the valve gap but how do you know when you have done enough? The valves do look good, there are no burned out spots. But in most cases, the seats are just smooth, grey and dirty looking.

I haven't checked the valve gaps yet but did slip a piece of paper between the push rod and the valve stem on the lapped valves to be sure that there was some gap. There was a gap in all cases. As a side comment, that lapping tool is not easy to use. The rubber cup is always slipping off the valve. There has to be a better way to turn the valves! Any comments will be appreciated. Ed
 
Local spots of a different color on the valve or seat show spots that haven't been affected by the laping. Put a small ammount of the compound on the valve face (completely around. Not a dab here & there) and put the valve in place. Using the suction cup tool rotate the valve rt. & lft. a few times ( 6/8) then lift the valve off the seat and give it about 1/2 a turn. Put it back down & repeat. Wipe totally clean and inspect. Usually it's a slightly dull continuous line on the valve & seat. It doesn't polish. It removes a bit of metal by abrasion. Again: it's a continuous un broken line you're looking for. Try a bit of oil on the suction cup + clean the top of the valve for better grip. No need to press down hard let the stuff do the work.
 
Make sure the valve head is clean then give it a shot of spit. If the rubber is really hard you can keep a cup of hot water nearby to dunk and soften it. As Charlie said, the only needed pressure is the weight of the valve and lapping tool. Do like an injun twisting a stick making a fire. Lift the valve out, make a 1/4 turn and repeat. Dont continue spinning in one direction. I am guessing you are using a medium or a fine grade of lapping compound? If you open the can and theres oil on the top stir it up really good.
If youre satisfied, clean the valve and the seat in the block 100% with some solvent and stick the valve back in the hole. You SHOULD NOT be able insert even a .001 feeler gage anywhere around the valve while exerting MILD pressure with your thumb. REPEAT: mild pressure.
While youre at it, inspect the springs, cups and pins. Replace as necessary. Are you doing this with the manifolds on or off? ws
 
I am using a fine dry compound mixed with oil to form a light paste. I am replacing all the springs, pins and seats. I will check tomorrow with a feeler gauge. Like what CharlieB describes I have a dull grey continuous line around the seat. Ed
 
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