lapping valves and seats necessary?
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lapping valves and seats necessary?
Hi,
I'm wondering if this is still necessary. The shop did my heads and tested the valves sealing, but some say that you still need to lap them with paste. Thanks.
I'm wondering if this is still necessary. The shop did my heads and tested the valves sealing, but some say that you still need to lap them with paste. Thanks.
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Re: lapping valves and seats necessary?
I usually only lap a valve to see where the valve is sealing on the seat, how high or low. Or you can slap them and see the mark on the valve. As far as sealing a seat with lapping compound, I don't think that is necessary, if you have good equipment. I check seats with vacuum, if the valves hold a vacuum, then they will hold compression. I always vacuum check new heads as I quite often see seats that leak from the factory.
Re: lapping valves and seats necessary?
Just get some Prussian blue and check for 100 percent contact and call it good but if a valve job was done they would have already done that and lapped them.
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Re: lapping valves and seats necessary?
My head guy laps them VERY LIGHTLY, but just to check seat contact.....NOT to help them seal.....
Mark Goulette
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Re: lapping valves and seats necessary?
I certainly won't lap valves with that "road gravel" valve lapping compound you get from the parts store.
I use 400 grit "Clover" polishing compound.
I use 400 grit "Clover" polishing compound.
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Re: lapping valves and seats necessary?
Are they a mirror finish?
Can't get any smoother then that.
Some materials won't, but that's their problem.
//
Magic marker/sharpie/whatever to see where they're mating.
Can't get any smoother then that.
Some materials won't, but that's their problem.
//
Magic marker/sharpie/whatever to see where they're mating.
Re: lapping valves and seats necessary?
I used to use that stuff, now I use gritty tooth paste. Works great.Walter R. Malik wrote: ↑Sun Dec 04, 2022 12:10 pm I certainly won't lap valves with that "road gravel" valve lapping compound you get from the parts store.
I use 400 grit "Clover" polishing compound.
Re: lapping valves and seats necessary?
Haven't seen anyone in this century lapping valves with grit compound.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: lapping valves and seats necessary?
Not seen YouTube? Plenty seem to think that a VJ and guides that have done 200k just needs some cheap paste and spin the valve until they mate
Re: lapping valves and seats necessary?
In the shop I was involved with....Using a VGS20 seat cutter, we would ocassionally see things like a Honda cylinder head exhaust seat need a slight touch up with laping compound. Those Honda valve seats were some hard stuff!
Re: lapping valves and seats necessary?
This is a very annoying question.
I'm not interested in insulting people who do things old ways.
VINTAGE speed is about re-living the past, so, that's ok. If people lapped valves in the 60's then maybe you want to do that too and see what it was like.
If you are just trying to do a GOOD job, and lapping IS necessary for you, please get better tools, is my opinion. Your wasting your time not having the right tools.
There is no advantage to grinding a groove in the valve face at all. Introducing abrasive is not good either, requires yet more cleaning.
If you cannot grind a seat good enough to run use a old valve for lapping if possible and keep refacing that valve again and again, if there is no other way.
I'm not interested in insulting people who do things old ways.
VINTAGE speed is about re-living the past, so, that's ok. If people lapped valves in the 60's then maybe you want to do that too and see what it was like.
If you are just trying to do a GOOD job, and lapping IS necessary for you, please get better tools, is my opinion. Your wasting your time not having the right tools.
There is no advantage to grinding a groove in the valve face at all. Introducing abrasive is not good either, requires yet more cleaning.
If you cannot grind a seat good enough to run use a old valve for lapping if possible and keep refacing that valve again and again, if there is no other way.
Re: lapping valves and seats necessary?
What are people using to clean the nasty stuff out of the pores ?
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Re: lapping valves and seats necessary?
Did you grind the seats or cut them?
Are the valves and seats concentric?
A very slight lapping will reveal seat contact width and concentricity.
But ultimately, I always rely on a vacuum seal test.
Are the valves and seats concentric?
A very slight lapping will reveal seat contact width and concentricity.
But ultimately, I always rely on a vacuum seal test.