Valve lapping
Thread Starter
Teching In
Joined: Jun 2021
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Valve lapping Hi.
I got the heads off the car. blown headgasket, so im chaning springs, lifters and getting a small cam upgrade.
So do i need to lap the valves, as I taken them out off the head to clean the carbon. The are going back in the same place (everything got labels on)
The engine got around 68k miles on it.
Thanks for the help.
I got the heads off the car. blown headgasket, so im chaning springs, lifters and getting a small cam upgrade.
So do i need to lap the valves, as I taken them out off the head to clean the carbon. The are going back in the same place (everything got labels on)
The engine got around 68k miles on it.
Thanks for the help.
Hi.
I got the heads off the car. blown headgasket, so im chaning springs, lifters and getting a small cam upgrade.
So do i need to lap the valves, as I taken them out off the head to clean the carbon. The are going back in the same place (everything got labels on)
The engine got around 68k miles on it.
Thanks for the help.
I got the heads off the car. blown headgasket, so im chaning springs, lifters and getting a small cam upgrade.
So do i need to lap the valves, as I taken them out off the head to clean the carbon. The are going back in the same place (everything got labels on)
The engine got around 68k miles on it.
Thanks for the help.
Thread Starter
Teching In
Joined: Jun 2021
Posts: 3
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Well the problem is I don't have a machine shop anywhere close to me. So this is becoming more of a learning process. I gotten alle the tools too check that the heads is still straight and they are completely fine. The head gasket went bad when the car was being parked as there was no overheating or anything. (Seen the crack in the passenger side gasket). The car would not start when I came back too it and all the coolant was gone.
I Was kinda wishing for that I could fix everything my self.
I Was kinda wishing for that I could fix everything my self.
TECH Addict
Joined: Dec 2017
Posts: 2,190
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The main thing valve lapping is good for, is making sure the seat and valve are concentric and that the valve isn't bent, by clearly showing the contact pattern.
On a "perfect" valve job it's only marginally useful. Doesn't really "do" anything as far as making it seal better or whatever.
For a used stock motor it's probably a good idea, stock valves being so fragile (relatively speaking), and specifically, easy to bend by overheating. If there's ANY ONE circumstance under which I would think that it's A Real Good Idea, it would be recovering from a severe overheating; and I would be paying particularly attention to the exhausts. Just make sure you use the FINEST grinding compound you can. There's one particular product out there that's SO abrasive, like 120 grit sandpaper, it's more like gravel than grinding compound. To the point that it's destructive. I think it's a Permatex/Loctite item but I could be wrong. I have an old can of Clover that's probably around 320 - 400 grit I would guess; I've probably done 40 or 50 sets of heads with it, and it's still ¾ full.
On a "perfect" valve job it's only marginally useful. Doesn't really "do" anything as far as making it seal better or whatever.
For a used stock motor it's probably a good idea, stock valves being so fragile (relatively speaking), and specifically, easy to bend by overheating. If there's ANY ONE circumstance under which I would think that it's A Real Good Idea, it would be recovering from a severe overheating; and I would be paying particularly attention to the exhausts. Just make sure you use the FINEST grinding compound you can. There's one particular product out there that's SO abrasive, like 120 grit sandpaper, it's more like gravel than grinding compound. To the point that it's destructive. I think it's a Permatex/Loctite item but I could be wrong. I have an old can of Clover that's probably around 320 - 400 grit I would guess; I've probably done 40 or 50 sets of heads with it, and it's still ¾ full.
Thread Starter
Teching In
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I see what you are saying RB04av, I'm just really scared off doing it as it is the first thing in this job I feel if I make a mistake it will have a huge impact. How reliable is the blue die method? I could maybe try that before doing any lapping or is that not good enough?
Also read somewhere that I can test the valve when I put the head together with some gas in the port and see if it drips on the other side. But that sounds about wonky too me?
Also read somewhere that I can test the valve when I put the head together with some gas in the port and see if it drips on the other side. But that sounds about wonky too me?
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The blue die method works but is harder to interpret.
The gasoline method works but also is hard to interpret. SOME gas is going to get through... how much is "too much"? You might get lucky and 14 valves hold it indefinitely but 2 just let it drain; but what if ALL 16 let just a little through? What should you do then?
Lapping shows you the actual contact pattern. Where the metal meets the metal. It's really the best way to illuminate visually, what's going on.
It's pretty eeeeezy. You can use just about any kind of FINE grinding compound, really. Even rubbing compound for paint would probably work well enough. Just put a dab of it on the surfaces, chuck the valve stem up in a drill GENTLY, and spin the drill for a few seconds in each direction while pulling up GENTLY on the valve to hold it on the seat.
Look for a pattern that's uniform width on the valve, and a uniform circumference on the seat. Most of the time it should be around .030" or so wide. On wore-out stock valves it'll be wider, on a new valve job it might be only .020" or so wide.
Don't worry about screwing anything up, it's really pretty simple. You'll see once get into it.
The gasoline method works but also is hard to interpret. SOME gas is going to get through... how much is "too much"? You might get lucky and 14 valves hold it indefinitely but 2 just let it drain; but what if ALL 16 let just a little through? What should you do then?
Lapping shows you the actual contact pattern. Where the metal meets the metal. It's really the best way to illuminate visually, what's going on.
It's pretty eeeeezy. You can use just about any kind of FINE grinding compound, really. Even rubbing compound for paint would probably work well enough. Just put a dab of it on the surfaces, chuck the valve stem up in a drill GENTLY, and spin the drill for a few seconds in each direction while pulling up GENTLY on the valve to hold it on the seat.
Look for a pattern that's uniform width on the valve, and a uniform circumference on the seat. Most of the time it should be around .030" or so wide. On wore-out stock valves it'll be wider, on a new valve job it might be only .020" or so wide.
Don't worry about screwing anything up, it's really pretty simple. You'll see once get into it.
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The blue die method works but is harder to interpret.
The gasoline method works but also is hard to interpret. SOME gas is going to get through... how much is "too much"? You might get lucky and 14 valves hold it indefinitely but 2 just let it drain; but what if ALL 16 let just a little through? What should you do then?
Lapping shows you the actual contact pattern. Where the metal meets the metal. It's really the best way to illuminate visually, what's going on.
It's pretty eeeeezy. You can use just about any kind of FINE grinding compound, really. Even rubbing compound for paint would probably work well enough. Just put a dab of it on the surfaces, chuck the valve stem up in a drill GENTLY, and spin the drill for a few seconds in each direction while pulling up GENTLY on the valve to hold it on the seat.
Look for a pattern that's uniform width on the valve, and a uniform circumference on the seat. Most of the time it should be around .030" or so wide. On wore-out stock valves it'll be wider, on a new valve job it might be only .020" or so wide.
Don't worry about screwing anything up, it's really pretty simple. You'll see once get into it.
The gasoline method works but also is hard to interpret. SOME gas is going to get through... how much is "too much"? You might get lucky and 14 valves hold it indefinitely but 2 just let it drain; but what if ALL 16 let just a little through? What should you do then?
Lapping shows you the actual contact pattern. Where the metal meets the metal. It's really the best way to illuminate visually, what's going on.
It's pretty eeeeezy. You can use just about any kind of FINE grinding compound, really. Even rubbing compound for paint would probably work well enough. Just put a dab of it on the surfaces, chuck the valve stem up in a drill GENTLY, and spin the drill for a few seconds in each direction while pulling up GENTLY on the valve to hold it on the seat.
Look for a pattern that's uniform width on the valve, and a uniform circumference on the seat. Most of the time it should be around .030" or so wide. On wore-out stock valves it'll be wider, on a new valve job it might be only .020" or so wide.
Don't worry about screwing anything up, it's really pretty simple. You'll see once get into it.
Banned
Joined: Oct 2020
Posts: 1,984
Likes: 682
Make sure the valves Straight.... 🤣
When my Ls3 heads were put together.... Aka FED just Did Port work. I was Told Lapping the valves Wasn't needed. I asked What does it hurt?
$$ do what I paid 4.
That on a head with Parts and a CNC. It's not about seeing a bent Valve with New parts.
Nothing major but Something that's not Over looked is Better.
When my Ls3 heads were put together.... Aka FED just Did Port work. I was Told Lapping the valves Wasn't needed. I asked What does it hurt?
$$ do what I paid 4.
That on a head with Parts and a CNC. It's not about seeing a bent Valve with New parts.
Nothing major but Something that's not Over looked is Better.
Banned
Joined: Oct 2020
Posts: 1,984
Likes: 682
What gets me is Big Words that mean What I said but it doesn't mean what I said ... 🖕 U. To Whom who said it.
con·cen·tric
of or denoting circles, arcs, or other shapes which share the same center, the larger often completely surrounding the smaller.
You spin the Valve to get ...them ConCentric aka Sealed and Matching one another. As the The Larger Valve sits inside ....the Seat & good Sealing Besides the Valve Job?
con·cen·tric
of or denoting circles, arcs, or other shapes which share the same center, the larger often completely surrounding the smaller.
You spin the Valve to get ...them ConCentric aka Sealed and Matching one another. As the The Larger Valve sits inside ....the Seat & good Sealing Besides the Valve Job?
Last edited by Corona; Jun 29, 2021 at 07:59 PM.
Launching!
Joined: Feb 2018
Posts: 225
Likes: 31
From: Bismarck, ND
Diy Hello,
I ported the heads, had a machine shop grind the valves and seats. A year later OVH the motor. Some of the seats became wider than the specs called for, so I ground down some extra valves at an angle to just hit the small diameter of the seats. Then oiled the guides, chucked the valve stem with a variable drill, on the installed valve with fine grinding compound on the seats. Which trimmed the seats up. If you just grind on the seat area, the seat width will be too wide, get poor heat transfer, cause bad flow and carbon will build up on them. On yours you could make a valve-angled for the larger diameter also.
Valve seat width, exhaust 1.78mm _ .07", intake 1.02mm _ .04". From 6.0L Service Manual.
To "grind" your seats, get some extra valves, put them in a drill press and use a counter rotating fine sander to change the angle.
If you have a light touch, you can take the pits out off the valve face this way also. But you have to check each one on the seat for yes con·cen·tric, just pop the valve down on the seat and pulled it out--- do not spin it--- to check for a complete seal, with your favorite goop on the seats.
1st thing to check is for warpage on the block [.008"] and heads [.003"]. I used a carpenter's level and feeler gauges. If you want to know how I decked my block, let me know.
Hope this helps.
I ported the heads, had a machine shop grind the valves and seats. A year later OVH the motor. Some of the seats became wider than the specs called for, so I ground down some extra valves at an angle to just hit the small diameter of the seats. Then oiled the guides, chucked the valve stem with a variable drill, on the installed valve with fine grinding compound on the seats. Which trimmed the seats up. If you just grind on the seat area, the seat width will be too wide, get poor heat transfer, cause bad flow and carbon will build up on them. On yours you could make a valve-angled for the larger diameter also.
Valve seat width, exhaust 1.78mm _ .07", intake 1.02mm _ .04". From 6.0L Service Manual.
To "grind" your seats, get some extra valves, put them in a drill press and use a counter rotating fine sander to change the angle.
If you have a light touch, you can take the pits out off the valve face this way also. But you have to check each one on the seat for yes con·cen·tric, just pop the valve down on the seat and pulled it out--- do not spin it--- to check for a complete seal, with your favorite goop on the seats.
1st thing to check is for warpage on the block [.008"] and heads [.003"]. I used a carpenter's level and feeler gauges. If you want to know how I decked my block, let me know.
Hope this helps.
Last edited by Metalchipper; Jun 30, 2021 at 05:02 PM. Reason: To make it clear as mud