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Exhaust valve lapping video

Lan Vinh Do

Well Known Member
Just want to share my experience.

I don’t know if i should have done more. I add 4 or 5 time some grinding compound. I took great care to clean everything after. Seat look better after then before.

Didn’t want to do too much as my compression was good before. Just did it because the valve had a hot spot. I may change the rotator cap too as they are cheap.

Any comment are welcome. Good or bad. Should i have done more grinding?

https://photos.app.goo.gl/LNgFfWFSN8Csfr4r6
 
Last edited:
Just want to share my experience.

I don’t know if i should have done more. I add 4 or 5 time some grinding compound. I took great care to clean everything after. Seat look better after then before.

Didn’t want to do too much as my compression was good before. Just did it because the valve had a hot spot. I may change the rotator cap too as they are cheap.

Any comment are welcome. Good or bad.

https://photos.app.goo.gl/LNgFfWFSN8Csfr4r6

That's very impressive. It looks like it got a lot better. What kind of camera are you using?
 
Just want to share my experience.

I don’t know if i should have done more. I add 4 or 5 time some grinding compound. I took great care to clean everything after. Seat look better after then before.

Didn’t want to do too much as my compression was good before. Just did it because the valve had a hot spot. I may change the rotator cap too as they are cheap.

Any comment are welcome. Good or bad. Should i have done more grinding?
The valve looked good but I may have missed the photo/video of the seat. The valve can look good by contacting only one side of the seat. It is rare, but I have encountered this. If the seat looked clean on full perimeter, then it is likely acceptable, but not 100.00% assured, the leak down test will tell. If you do it before installing the rockers, then a brass hammer tap on the tip to seat it a few times will ensure it is ready for test. Not hard, just enough to lift off the seat. The valve never drops to the seat in operation, the cam lowers it. At this point you have done all that can be done short of disassembly and "precision" machines.

Good choice on rotator replacement.
 
Last edited:
The valve looked good but I may have missed the photo/video of the seat. The valve can look good by contacting only one side of the seat. It is rare, but I have encountered this. If the seat looked clean on full perimeter, then it is likely acceptable, but not 100.00% assured, the leak down test will tell. If you do it before installing the rockers, then a brass hammer tap on the tip to seat it a few times will ensure it is ready for test. Not hard, just enough to lift off the seat. The valve never drops to the seat in operation, the cam lowers it. At this point you have done all that can be done short of disassembly and "precision" machines.

Good choice on rotator replacement.

The best view of the seat is here. I was unable to get all the 360.
The compression was 78/80 before. I only did it because of the hot spot on the valve at a random borescope while i was cleaning the plug.

Seat cylinder # 1

https://photos.app.goo.gl/hJR97qc6RAkzpX958

Picture Hot spot on the valve #1

https://photos.app.goo.gl/kc3jTbMenp1uAF2U6
 
The best view of the seat is here. I was unable to get all the 360.
The compression was 78/80 before. I only did it because of the hot spot on the valve at a random borescope while i was cleaning the plug.

Seat cylinder # 1

https://photos.app.goo.gl/hJR97qc6RAkzpX958

Picture Hot spot on the valve #1

https://photos.app.goo.gl/kc3jTbMenp1uAF2U6

I have looked at all your photos and posts. I still cannot see the seat well enough, but no matter. You did what you could. If the seat was observed in full perimeter and the valve made contact and left buff from the grinding. That is all you can do. It is probably all reassembled now, so just recheck via leak down and run it for 20 hrs, keeping an eye on the EGT relative to its other friends. Based on what is seen and posted, the probability is very high the hot spot will disappear. IMO that is. The engine will always tell the truth, although sometimes it is sneaky.
 
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