Topic: Lapped valves leak - what to do?

[70CB750]

Yesterday I finished lapping my valves, but due to family logistics I did not test them for leaking yet.

Now let's say they DO leak, gotta lap some more or what is the correction here?

I recut valve seats with Neway cutter and lapped with coarse and fine compound (JEG), on close inspection there is a nice grayed stripe on each and every seat/valve.

[Bru-tom]

get your hands on some engineers marking blue. its a paste that you rub on one surface, then you rub the two together, there should be an even amount on both surfaces and no dark or light spots. its what i used when i did mine, they came out 100%.

[MoMo]

Usually, if lapping does not seal, seats need to be recut but as bru-tom says bluing will show is that is necessary

[flybox1]

channel this guy while you're doing it...

[lrutt]

if ur guides are within spec and you've lapped and cleaned the seats REAL GOOD, this should be a no brainer. If you do find one that leaks, give a few taps with a soft faced hammer to un-seat then seat. If it still leaks then you need to assess why.

[Bankerdanny]

I thought you only apply the blue to the seat side, then lap and look for a nice clean uniform ring on the seat

[lucky]

I thought you only apply the blue to the seat side, then lap and look for a nice clean uniform ring on the seat

You can use a black magic marker. Same result.
You apply the ink to the seat ,that is correct.

[Vinhead1957]

You mark the valve! Lines across the surface (perpendicular) lap the valve and check that all lines are worn off evenly

[70CB750]

Thank you, guys. I used blue before, that is not a new concept for me.

I wanted to know if the leaks calls for more lapping or cutting - thanks, Larry.

[Don R]

It depends on the pattern you see. If you did it correctly I doubt there will ba a problem.