faster way to lap valves - Page 2 - Alfa Romeo Bulletin Board & Forums

  #16 (permalink)  
Old 01-19-2007, 06:15 AM
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I agree with the warnings about using a drill motor instead of hand lapping. And that lapping is not a cure-all for bad valves/seats.

When I used the drill motor method it was:

1. merely to clean up a bit of corrosion & carbon.
B. I ran the drill motor at a very slow speed & used a lift, lap, lift, lap technique.
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  #17 (permalink)  
Old 01-19-2007, 06:37 AM
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Hand lapping is the way. My Autoshop teacher taught us this method for seating reground valves. Worked on the old Model T I found in the desert and rebuilt for my final project in '67, and every other engine I have done a valve job on since. Just take your time and check often.
Good luck.
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  #18 (permalink)  
Old 01-19-2007, 08:16 AM
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Quote:
Originally Posted by ossodiseppia View Post
I watched the late Gary Valant lap valves. He did it by hand. His technique envolved holding the lapping tool between the palms of both hands and rolling it back and forth. It's the same way you were taught to light a fire in boy scouts.
thats how I do it. On my valves on my supposedly reconditioned head, the seats were pretty nasty looking; thought they needed a grind but after a second or two of lapping with fine compound, they looked great. one thing about the tools with crummy suction cups, clean the valve face very well so there is no oil and same with the suction cup, then put a [I]small[I]
bit of spit on it and go carefully. It'll fall off of course but just keep at it.
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Old 01-19-2007, 08:38 AM
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Originally Posted by genericwood View Post
Now I don't know if this is critical or not, but I was always taught to not "spin" the valve in its' seat when hand lapping. The reason given was that this can create circumferential (is that a word?) grooves in the seat. Rather, I was taught to turn the valve through an arc of 120-180 degrees and rotate the position occasionally.

Am I the only one taught this way?

Erik
That is the method I was taught in the automotive machine shops and in an apprentice machinist program, and have been using for years.

And as has been posted, it is one method to determine the efective seat width; blueing also does the same.
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  #20 (permalink)  
Old 01-19-2007, 09:47 AM
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I have a nice, and really old, snap on lapper. You turn the handle and the lapping suction cup turns on full turn each direct, it doesnt spin, but instead goes one full turn one way, then one the next way, very useful. The guy i bought by valve grinder from gave it to me as a freebie.
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Old 01-19-2007, 12:57 PM
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Changed my mind.....I'm NOT putting it on a drill, just to "whip" the stuff around and risk ruining the stem spec. I will rub by hand like some described, periodically shifting position. (here comes the blisters)
Joe Papa Sr
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Old 01-19-2007, 01:17 PM
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Osso is right in the way he was taught.
You should NOT use a drill. It causes radial grooves I was always told.
Years ago I had a valve lap tool that went in a drill and it turned the valve abot 45 deg each way. It worked well and I never had any probs with the heads I did after.
Use the sucker on a stick as Osso says. Put some course compound on... just a little, as you dont want it anywhere near the guides. Spin, lift and turn the valve thru 90 deg as you lift. The valve should be lappped and perfectly seated thru 360 deg when you are done. I remember giving the valve a little tap as I relapped every turn to drive the squeezed out compund onto the seat.
When it looks a dull gray and is touching down all round, clean it up well and repeat with fine compound.
Then you are done!
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Last edited by Keyspider; 01-19-2007 at 01:23 PM.
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Old 01-19-2007, 02:51 PM
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I use extra thick blue latex gloves (available at advance auto parts & Snap On truck) but nitrile will work as well (commonly blue). These will make a big difference in preventing blisters, not to mention better control of the stick via better grip.

If you want to drive to md, you can borrow my lapper
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  #24 (permalink)  
Old 01-19-2007, 03:57 PM
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Blisters!?!?!? We're talking lapping here, not grinding into oblivion. Lapping need not take more than a minute or so per valve.
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Old 01-19-2007, 08:25 PM
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mabe they're delicate

Personally I don't worry much about it unless my hands are covered in open flame, but hey.......
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Old 01-19-2007, 10:14 PM
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My fathers shop used to have seat and valve refacing tools ... really simple.

Thus if your seats are that bad, they might not need replacing just get them recut ... does not take that long.

Also we used to reface the valves too, that was a bit more exciting .

BTW: Engine reconditioning shops don't lap anymore ... too much labour and too much seat contact. The seats are made with a point (I think) and the valve wears it's way in to get the ideal 1/3rd face width contact. No need to lap. I also think this has a lot to do with improved machining tolerances.

Pete
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Old 01-19-2007, 10:56 PM
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A good valve grinder will cut the seats with 3 cuts and then hand lap for a finish to check for proper seating on the valve face. I have heard that there is a 1 deg interference fit between the seat and the valve.
I touch up with the heavy compound and then finish with the fine. Then throughly wash the head before assembly.
I have used a drill on the "dumb-dumb" stick. This is what it was called when I learned to hand lap valves. I don't recommend the drill. The stick is great for making your hands very sore. It was the best way to get that back and forth hand lap. After a few twists of light pressure, you picked it up and moved it around a bit and started again to get new grit on the valve face.
I found this is a great way to get the valves to seal tighter after a valve job.
I am to the point where I want to get one of those mechanical devices for lapping valves.
Don't get compound on the stems of your valves, it is a sure way to ruin valve guide clearances!
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  #28 (permalink)  
Old 01-20-2007, 05:30 AM
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Quote:
Originally Posted by Keyspider View Post
Osso is right in the way he was taught.
You should NOT use a drill. It causes radial grooves I was always told.
Years ago I had a valve lap tool that went in a drill and it turned the valve abot 45 deg each way. It worked well and I never had any probs with the heads I did after.
Use the sucker on a stick as Osso says. Put some course compound on... just a little, as you dont want it anywhere near the guides. Spin, lift and turn the valve thru 90 deg as you lift. The valve should be lappped and perfectly seated thru 360 deg when you are done. I remember giving the valve a little tap as I relapped every turn to drive the squeezed out compund onto the seat.
When it looks a dull gray and is touching down all round, clean it up well and repeat with fine compound.
Then you are done!
That grey appearance you mention, thats what Im getting...seats are smooth now, but a flat grey. I was expecting a mirror finish. Using permatex all in one compound. starts out as 80 grit, then goes up to 180 or so, the tech said on the phone. He was not very helpful, otherwise. Seemed REALLY reluctant to say much, like he was on trial!!!!
Joe
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  #29 (permalink)  
Old 01-20-2007, 09:57 AM
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Found this on the web...

"When valve faces and seats have been re-faced and re-cut, or if they are determined to be in good condition, the valves must be "lapped in" to ensure efficient sealing when the valve closes against the seat.

Invert the cylinder head so that the combustion chambers are facing up.

Lightly lubricate the valve stems with clean oil, and coat the valve seats with valve grinding compound. Install the valves in the head as numbered.

Attach the suction cup of a valve lapping tool to a valve head. Moisten the suction cup to securely attach the tool to the valve.

Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving. Lap the valve until a smooth, polished seat is evident (you may have to add a bit more compound after some lapping is done).

Remove the valve and tool, and remove ALL traces of grinding compound with solvent-soaked rag, or rinse the head with solvent.

Valve lapping can also be done by fastening a suction cup to a piece of drill rod in a hand "eggbeater" type drill. Proceed as above, using the drill as a lapping tool. Due to the higher speeds involved when using the hand drill, care must be exercised to avoid grooving the seat. Lift the tool and change direction of rotation often."


Thats what I do anyway!
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Last edited by Keyspider; 01-20-2007 at 10:03 AM.
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  #30 (permalink)  
Old 01-20-2007, 01:02 PM
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Sorry bout my obviously erroneous info (I was one of the drill guys). Mine was info passed from one shade tree mechanic to another and I figured if it was wrong someone would speak up. I guess I lucked out that it seemed to work in my case. It was a bit of a hodge-podge engine anyway.

Bill
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