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Lapping valves

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Rut

Rut

Obi Wan
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Im working on my 1275 head this morning, lapping valves, cleaning and testing the results in preparation for finishing the head. Years ago I used a valve lapping tool with suction cups on the end and still have a set, but this time I used an electric screwdriver and a piece of 1/4" tubing to connect to the valve and finger pressure on the face of the valve to control pressure. This was about as quick and easy as anything could be and all the marks are good on both the valves and seats. When testing my handy work I used denatured alcohol since it leaves no residue and can escape thru tiny spaces. I used the weight of the valve only, no springs and had minor leaks on #8, 3, and 2 which I will lap again. I feel good about the process and the results, but is this the proper way to test for leaks? I know that static results can vary from real life of a running engine. Thoughts?
Thanks, Rut
 
Wouldn't a leakdown tester tell you if your valves were leaking? Assuming your rings are good, if the leakdown tester is showing excessive leakage, it may be valves out of adjustment?

I just did a valve adjustment on Baby Blue. It made a very big difference!
 
This is on a new engine build and the head is on the bench. I managed to get a leak free fit with just the weight of the valve after lapping and will recheck once the springs are installed. I used a variable speed screwdriver on low speed reversing direction multiple times. I'll post pictures of the set up.
Thanks, Rut
 

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Used hand lapper for years until the came out with battery operated screwdrivers. Good job.
 
I think it sounds like a great method as long as you remembered to lift the valve head off the seat and reverse direction frequently. The alcohol was a good choice also. I like the idea much better than the suction cup sticks or hand powered oscillating lapping tools. I could never keep the suction cups in place well and the cups seem to fail relatively quickly (from rot) during storage. If you got a good seal with the weight of the valves alone I'm confident you will see the same (or better) with the springs installed.
 
Doug,
Surprise, surprise! I have 3 leakers after the springs were installed! Nothing major, just a little dampness around the guide on the chamber side, but I'll clean it up anyway since I've got plenty of time.
Rut
 
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