Lapping valves the lazy man's way.

I gave up on lapping after leak down testing failed repeatedly. Concentricity of the seats was just to far gone . So bought some used valve and seat equipment, a 1940's Van Norman valve grinder and then picked up a Black and Decker seat grinder and several stones plus the stone sharpener shaper and pilots . Works well but if the guides are not replaceable and worn opens a whole new can of worms.
With stones ground correctly the seat width and position can be brought back into spec as well.
It IS nice when valve and seats aren't worn badly, so that they can be lapped to a good seal. Glad it worked for You and for many but did not on the last couple engines for me.
 
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th62 said:
when you rub two pieces of metal together with an abrasive between them, you are removing metal.
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The way you’re doing it, sure.
 
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Have use the old suction cups on the rod by hand, Then had one that looked like an old egg beater that had a suction cup on one end, and it did the back and forth for you, Then when that broke, Put a piece of tube on it and used it on the valve stem, and pulled against it to get the job done, Just had do remember to push down instead of trying to lift. Then the last thing I tired was a gyro electric srew driver, As you turned our hand one way or the other it reversed directions. (easier on the hands). Where there is a will there is a way. You just want todo enough to make sure you have a good seal ring all the way around.
 
455dan said:
I gave up on lapping after leak down testing failed repeatedly. Concentricity of the seats was just to far gone . So bought some used valve and seat equipment, a 1940's Van Norman valve grinder and then picked up a Black and Decker seat grinder and several stones plus the stone sharpener shaper and pilots . Works well but if the guides are not replaceable and worn opens a whole new can of worms.
With stones ground correctly the seat width and position can be brought back into spec as well.
It IS nice when valve and seats aren't worn badly, so that they can be lapped to a good seal. Glad it worked for You and for many but did not on the last couple engines for me.
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If the guides are a part of the cylinder, you can bore them out to the appropriate size and press in replaceable guides.
 
th62 said:
If the guides are a part of the cylinder, you can bore them out to the appropriate size and press in replaceable guides.
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Oh Yeah, well aware of that, I have watched ebay and elsewhere for years for an 11/32" K line thin wall kit at a fair price, but at an average price between 5-900 bucks, I am not biting. That boring also needs to be accurately located in relation to the existing seat. More recently I did get a small HF Knee Mill but not sure whether there is enough room in the z travel to be able to do guide work on the heads.
 

The reason you're having to resort to mechanical means is you are not lifting the valve to let fresh compound get in. You're rubbing metal on metal with grease (The paste base) and just making the valve dizzy. On properly cut seats with properly ground valves it should take no more than 5-10 seconds per valve. The cleanup usually takes longer than the process.
 
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th62 said:
Yes, the problem would be finding a machinist that knows what he's doing, very difficult task.
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Funny you should say that...

I took a few heads to our small towns auto machinist shop reassembled my valve jobbed head and it was no better than when I took it off.
after further inquiry the NEW shop machinist who replaced the long time person I trusted and done several heads for me, admitted that he only ground the valves and lapped them into the existing seats I asked where is the seat grinding equipment and then he admitted they no longer had any...

over $250 wasted on my 55 HP tractor... He said I did a Valve job on your head and I never said the seats were ground I just said I did the seats, and that means lapping.

With that said in the future I will ask more questions on what equipment will be used and what their experience is.

I trusted a shop that had done good work in the past Including even Pontiac SD 455 heads with excellent results.

My mistake was not verifying the new persons actual qualifications. Or with help from sites like this I will re do the previous work at least on my tractor myself since It has replaceable guides and I did precure everything needed to fix the auto machinists so called professional work.
 
When I had the barrel rebored, I also got the guy to reseat the valves, as they were badly pitted. When I picke the head and barrel up, he told me I wouldn't need to lap the valves, they were perfect.
Silly me believed him and never checked. First time I've ever outsourced a job. Engine ran for a while, but eventually stopped. When I tested by pumping air into the combustion chamber, the valves leaked like a sieve, and when I pulled the head off the inlets were sooted up badly.
 
Lapping valves 'properly' will take considerably longer than a few seconds, how long is dependant on how bad the seats are. The more hours on a motor, the worse the seats will be. Lapping valves is a three stage process: Grinding with course compound, finishing with fine compound and finally testing for leaks.

There are different grits in valve lapping compounds, so, it's not just a single operation, start with course and finish off with fine. Before finishing with the fine grit, make sure you remove all the old course grit. If you just use course, the valves will leak. As you lap, some of the abrasive in the compound will break down into finer particles, so, you will have a mixture of fine and course particles, the course particles will form very fine grooves in the seats, so, you will have to lift the valve every now and then, wiping the seats clean to remove the lapping compound and replace with fresh compound, you also need to change the direction of rotation every now and then.

It is also a good idea to squirt a bit of oil into the valve guides before inserting the valves. This will lubricate the stems providing less friction as the valve is rotated.

When testing, invert the head, make sure the seats on valve and cylinder head are spotlessly clean, replace the valves and turn them by hand against the seats a few times to ensure they are seating properly. Then pour petrol into the combustion chamber, place a sheet of metal over the top to stop,the petrol evaporating and let it sit for a few hours to see if it leaks. Don't use water, water is denser than petrol so is less likely to show any leaks. Water reacts with steel and will form rust spots on valves and any steel it contacts, including the seats.
 
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