Author Topic: Lapped valves leak - what to do?  (Read 2925 times)

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Offline 70CB750

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Lapped valves leak - what to do?
« on: December 16, 2013, 06:13:00 AM »
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.
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Offline Bru-tom

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Re: Lapped valves leak - what to do?
« Reply #1 on: December 16, 2013, 06:18:36 AM »
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%.

Offline MoMo

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Re: Lapped valves leak - what to do?
« Reply #2 on: December 16, 2013, 06:31:42 AM »
Usually, if lapping does not seal, seats need to be recut but as bru-tom says bluing will show is that is necessary

Offline flybox1

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Re: Lapped valves leak - what to do?
« Reply #3 on: December 16, 2013, 07:15:10 AM »
channel this guy while you're doing it...
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Offline lrutt

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Re: Lapped valves leak - what to do?
« Reply #4 on: December 16, 2013, 09:59:29 AM »
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.
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Offline Bankerdanny

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Re: Lapped valves leak - what to do?
« Reply #5 on: December 16, 2013, 10:05:53 AM »
I thought you only apply the blue to the seat side, then lap and look for a nice clean uniform ring on the seat
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Offline lucky

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Re: Lapped valves leak - what to do?
« Reply #6 on: December 16, 2013, 10:35:08 AM »
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.

Offline Vinhead1957

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Re: Lapped valves leak - what to do?
« Reply #7 on: December 16, 2013, 12:32:54 PM »
You mark the valve! Lines across the surface (perpendicular) lap the valve and check that all lines are worn off evenly

Offline 70CB750

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Re: Lapped valves leak - what to do?
« Reply #8 on: December 16, 2013, 12:43:56 PM »
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.
Prokop
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Offline Don R

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Re: Lapped valves leak - what to do?
« Reply #9 on: December 17, 2013, 12:15:14 PM »
It depends on the pattern you see. If you did it correctly I doubt there will ba a problem.
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