How To: Lapping Your Valves At Home - Team Camaro Tech
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Old Nov 13th, 17, 07:47 AM   #1 (permalink)
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How To: Lapping Your Valves At Home

For the most part LS heads are very good quality, you find that most (even higher mileage units) do not require a valve job. If you are swapping on a used set, and want to save some $$$ at the machine shop, here is an alternative for you. I hope this gives you an understanding of valve sealing, and saves you some money.

These heads were taken to a machine shop. They were cleaned and milled lightly but no other work was performed. The bill was around $80.



Here's an intake valve. Notice the silver streak around the lower edge. That's where it seals to the valve seat in the head. We are gonna freshen that surface and hopefully widen it some for a better seal.



Take your compound, and spread it like so. Doesn't have to be perfect.



Stick it into its hole and clamp your drill onto the stem so you can use the drill to spin the valve in the head.



Use the slow speed setting on your drill, and move it in and out (on and off the seat). Wow what a difference 20 seconds makes.



Comparison.



The sealing surface in the head.



Exhaust valve comparison. A little pitting on them is normal and nothing to worry about. Once i mate a valve to a hole, it stays there. I dont move it around once its been ground in. Also make sure you wipe as much of the compound off the head and valve as you can when youre done and hit the valve stem with some wd40 to help it slide in the valve guide easier.



Thats it, repeat the procedure for all 16 valves, makes sure you have a nice even band around each valve and you're good. If one looks off or not even all the way around check the valve and see if its bent slightly. Any questions just ask.
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Old Nov 15th, 17, 06:29 AM   #2 (permalink)
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Re: How To: Lapping Your Valves At Home

If you want to lap your valves go for it but it accomplishes next to nothing. Once you start the engine heat will change the valve and seat mating geometry, if the guides are not new and properly installed the lap will be crooked.
Lapping is fine if you are trying to pawn off a questionable motor on a sucker but it isn't going to give you any extra HP.
As for residual lapping compound, you better get rid of all of it by cleaning not wiping or you will be wiping your bearings. We stopped lapping years ago in the industry.
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Old Nov 18th, 17, 06:36 AM   #3 (permalink)
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Re: How To: Lapping Your Valves At Home

I shoulda figured a thread like this would bring the so called experts out of the woodwork. Ive done this a ton of times, never "wiped a bearing" and never had "lap will be crooked". I don't even know what you're talking about. How about just go sit in the corner for a while. You can't even figure out that i didn't do this to "give you any extra hp"


Bottom line is this, I assembled another engine 3 days ago. After seeing some responses i decided to look closely at the used valves and their sealing surfaces, and be objectionable. What i found was the valve seats were in really nice shape (131k miles) and the intake valves were in nice shape, but the exhaust valves were heavily pitted. And that is exactly why you do this. They WILL seal better after being scuffed vs installing as is.
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Old Nov 18th, 17, 07:29 AM   #4 (permalink)
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Re: How To: Lapping Your Valves At Home

Quote:
Originally Posted by 01ssreda4 View Post
I shoulda figured a thread like this would bring the so called experts out of the woodwork. Ive done this a ton of times, never "wiped a bearing" and never had "lap will be crooked". I don't even know what you're talking about. How about just go sit in the corner for a while. You can't even figure out that i didn't do this to "give you any extra hp"


Bottom line is this, I assembled another engine 3 days ago. After seeing some responses i decided to look closely at the used valves and their sealing surfaces, and be objectionable. What i found was the valve seats were in really nice shape (131k miles) and the intake valves were in nice shape, but the exhaust valves were heavily pitted. And that is exactly why you do this. They WILL seal better after being scuffed vs installing as is.
Don't let it bother you bud. Most people are going to read this and see the value in it and be helped by it. Let the trolls be. The good thing is you have provided a service by posting helpful information and that is really all we can do. Thank you for sharing.

Besides, using the logic of the responder it wouldn't do any good to have the seats cut at the machine shop either because they would move around when the engine heats up. Bogus. Measure the guides with a ball mic, if if they check good you will get good results. If using a power drill bothers someone, you can use an old school lapping tool with the suction cup that goes on the valve head. It's just a lot more elbow grease as you and I both know.
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Old Nov 18th, 17, 08:23 AM   #5 (permalink)
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Re: How To: Lapping Your Valves At Home

Quote:
Originally Posted by 327fuelinjected View Post
If you want to lap your valves go for it but it accomplishes next to nothing. Once you start the engine heat will change the valve and seat mating geometry, if the guides are not new and properly installed the lap will be crooked.
Lapping is fine if you are trying to pawn off a questionable motor on a sucker but it isn't going to give you any extra HP.
As for residual lapping compound, you better get rid of all of it by cleaning not wiping or you will be wiping your bearings. We stopped lapping years ago in the industry.
Ok so all trolling aside who's right?
To the o.p. I think the pics and story are great, I will never lap my valves only cuz I just drop off my heads and pay the bill and bolt them on.
Being politically correct has made this forum boring, it makes people not want to express their thoughts with fear from the morality police.
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Old Nov 18th, 17, 08:26 AM   #6 (permalink)
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Re: How To: Lapping Your Valves At Home

Im upfront and honest. I dont give two s h i ts what his old school way of thinking has him doing. I shoulda snapped pics of the exhaust valves, you could tell there was almost no more flat sealing surface left due to heat pitting. That is common sense, and anyone armed with that info can clearly see who is right and who is wrong.
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Old Nov 18th, 17, 05:52 PM   #7 (permalink)
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Re: How To: Lapping Your Valves At Home

Quote:
Originally Posted by 01ssreda4 View Post
Im upfront and honest. I dont give two s h i ts what his old school way of thinking has him doing. I shoulda snapped pics of the exhaust valves, you could tell there was almost no more flat sealing surface left due to heat pitting. That is common sense, and anyone armed with that info can clearly see who is right and who is wrong.
Actually I do have common sense, what I don't have is knowledge of of what happens to a valve in an engine as it heats up. I think your advice is sound but I am no engineer. Just curious if the disgruntled one is making a valid point. Please realize I meant no offense to you or anyone else whatsoever.
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Old Nov 18th, 17, 06:22 PM   #8 (permalink)
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Re: How To: Lapping Your Valves At Home

It would be interesting to see before and after compression/leak down test after the lapping process. My experience says a waste of time however I always remain open minded.

I also figure if I have a high mileage motor and the heads are already off why not just do a valve job.

The other issue in LS engine is the valve guides which I would be more concerned about then the seats. You really donít want to drop #7 which runs hotter and is more susceptible to failure. Even more so if you do a cam swap.
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Old Nov 18th, 17, 06:40 PM   #9 (permalink)
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Re: How To: Lapping Your Valves At Home

Literally no one I know has EVER had valve guide issues....and most of us run stock heads for extended periods of time,, and most of us have had multiple LS powered cars. These motors are very good from the factory as far as that goes. I too would love to see hard results....hey maybe I can arrange that during my next head swap.
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Old Nov 18th, 17, 07:01 PM   #10 (permalink)
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Re: How To: Lapping Your Valves At Home

Read about LS7s dropping valves. Most likely due to play in the valve guides.

Stock heads are fine. Need springs with high lift cams and think about the trunion upgrade to be on the safe side
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Old Nov 21st, 17, 08:01 AM   #11 (permalink)
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Re: How To: Lapping Your Valves At Home

I could care less what you do, it is your engine, I only tried the point out how it is done professionally and why lapping isn't done anymore. Go see what your local speed shops are doing. If you don't know what valve grinding compound left in an engine will do or what an out of round valve guide is you better do some research, I offered some tips to
keep your engine running but you decide attack some because they offer a different idea or solution, I think it is you who have the problem.
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Old Nov 21st, 17, 08:06 AM   #12 (permalink)
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Re: How To: Lapping Your Valves At Home

We dont even have speed shops here. None that I would trust anyway. I think others may be in a similar situation. Anything you grind is gonna throw off the equivalent of powdered sandpaper everywhere. That is turn accelerates engine wear 10 fold until its gone. How long does it take to dissipate? I dont know and dont care.
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Old Nov 21st, 17, 08:44 AM   #13 (permalink)
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Re: How To: Lapping Your Valves At Home

I lapped the valves on a model A once. Also used cardboard and permatex for a head gasket on the side of the road to get us home.

Both very short term solutions.

#1 engine building rule is keep everything as clean as possible.
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Old Nov 21st, 17, 08:46 AM   #14 (permalink)
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Re: How To: Lapping Your Valves At Home

The head is off. Its not rocket science to clean the valve grinding compound off the head and valve. Would literally take 10 secs. Thats making a huge deal out of nothing.
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Old Nov 21st, 17, 09:56 AM   #15 (permalink)
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Re: How To: Lapping Your Valves At Home

If I have a used set of heads that I'm putting back on a motor, I lap the valves too. #1 I like to do things myself when I can. #2 Machine shops cost money and time. They aren't always right up the street. I don't use the drill though. I hand lap them. Maybe it helps, maybe it doesn't, but I'd rather have a nice clean seat and lifter face like they're supposed to have either way.
I think the clean rule goes without saying, but as long as you clean up like you're supposed to it's a non-issue IMO.

Not an LS motor, but same premise... Every little bit helps.










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