Valve lapping question

[sihi]

Hi. I a was today first time lapping valves actually 1 valve.This valves was not servicing last 25 years. It take 2 hours to do one valve with classic lapping stem and I am still not sure if is good enough , because on valve is very tiny black spots which I can't get off. Valve seat is perfect. Is it necessary to have perfect shiny valves or like this is enough. Amount of time spent on one valve try my patience to border. Exist any quick seal test without mounting spring ?

 

[geol]

Hi. I a was today first time lapping valves actually 1 valve.This valves was not servicing last 25 years. It take 2 hours to do one valve with classic lapping stem and I am still not sure if is good enough , because on valve is very tiny black spots which I can't get off. Valve seat is perfect. Is it necessary to have perfect shiny valves or like this is enough. Amount of time spent on one valve try my patience to border. Exist any quick seal test without mounting spring ?

View attachment 45513

I use a lapping tool that has a suction cup BUT has a piston and a knobbed rod you pull out and it holds the work very tightly. The body is round and you can put the tool between your palms and it makes fast work of the lapping. You can also buy different grit compound.

The valve you show shouldn't have the black spots which appear to be pitting as this valve won't seal as well with a cleanly lapped surface without the spots. If I had that valve, I would media blast it with fine bead and see if I could get some of that stuff out of the sealing area. If you buy new valves (I would if the surface can't be made right), make sure to measure the lengths for spec... they often need tipped to be within spec.

 

[Nessism]

Lapping is a process to remove very slight imperfections in the valve and seat. It is not to recondition the parts. Lapping should take 2 minutes, not 2 hours.

Your photo shows deep pitting in the valve, AND it looks like you have been heavily lapping the valve into the seat because it looks like a ridge has form. This is not good.

I recommend that you find a shop with a "centerless" valve grinding machine and have the valves dressed. Every good automotive machine shop should have this kind of equipment. After the valve face is cleaned up be sure to have the valve stem tip ground too otherwise you may find the valve shims are all going to be too thin. This only takes a couple of minutes each valve so the shop shouldn't charge too much.

Good luck.

 

[tkent02]

Ed, what does the "centerless" mean?

 

[Nessism]

Ed, what does the "centerless" mean?

Tom, it relates to grinding where the piece is not held tightly in a chuck. It sort of floats between two different wheels.

 

[tkent02]

Interesting, thanks.

 

[Nessism]

The guy that made that video did my valves. He did it while I waited and only charged me a few bucks. After seeing how sweet they turned out I now have the valves ground as a matter of course when redoing a head.

BTW, check out that guys You Tube videos. Lots of super cool stuff.

 

[Big T]

Ed, as usual, is correct

When you lap a valve, the contact area on the face should only be 2-3mm wide, not the entire face as in the picture

you may need a new valve, which may be cheaper than 2 machinings

 

[sihi]

I measured face and is 1.89mm. Here in Norway is nothing cheap. I have to find another solution or just live with it. I find microscopic scratches on stem I am sure I cleaned everything really good .

 

[sihi]

is that enough to buy new one?

 

[tkent02]

No, it will be fine.

 

[sihi]

I run today leakage test only for that valve which I was lapping so long. I filled up exhaust with gasoline. After 15 min. nothing totally dry . After 4 hours was very slightly wet but no any dripping or leakage. Since is my first test I really appreciate any comment on that results.
Thank you to everybody

 

[tkent02]

Should be fine. If anything it will seal a little better after it runs a while.