The Correct Way To Lap Engine Valves In

I used that technique about 40 years ago on my first car. It worked fine. I simply wrapped the top of the valve stem in some thin sheet copper (to prevent hurting the top of the valve), turned on the drill, and moved the drill up and down in a bumping motion against the seat.

If you just pull the drill tight against the seat and turn it on, you could start to build up a lot of heat. Not good for the valve or seat.

Just don't take it too far. It's pretty easy to grind off too much using a power tool.

One other thing: After doing that, I used a cheap "sucker on a stick" for a few passes.

If a short bit of rubber pipe is used to couple the valve to the drill, then I don't see a prob, especially as most drills can be reversed, you'd want to run fairly slow, lift the valve on and off the seat and check it regularly. I don't s'pose they are hand lapped at the factory.
Del

As a machinist, I don't see a problem with that. Perhaps we use the little stick because we've always done it that way

As a machinist, I don't see a problem with that. Perhaps we use the little stick because we've always done it that way

I think thats the reason, drills would not have been around when engines were first born, and the only way to lap the valves in would have been to use a stick.

as long as no weight is placed on the valve stem, and as others say a slight bumping action to move the paste around has worked well for me, and as i have said i have tried both methods and even on a test some years ago, i did both and the assesor didnt spot it.

if there is a reason why it should be the old way i would listen.

Just a thought how would valve reseating be undertaken on valves on other applications be resurfaced ?

http://www.google.co.uk/search?q=hand+lapping+valves&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GZEU_en&redir_esc=&ei=QrF2TJXZAojW4wbHxImBBg

I'd say if it's the first time you've ground valves, do it by hand! This limits the down force you can apply.

After you've done a few, then bring out the drill.

valve seat angles

http://www.google.co.uk/search?q=valve+seat+angles&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GZEU_en&redir_esc=&ei=mLJ2TKPXAt6T4ga2_cn9BQ

I never knew there was any other way to do it than with a drill untill I went through the John Deere Agricultural Technologies program.

Someone used to make a tool which acted like a drill for this application, but the motion was oscillating back and forth, instead of just simply rotating.

The tools are still available here.

As already mentioned, the valve lapping technique worked well on old engines but newer cars all have hardened valve seats so the lapping will only manage a very light cut.

In my late grandfather's tool chest there is one of these valve lapping tools you describe. It is not an attachment to a drill as referenced by Nigh (Post #11), but a hand cranked, self-contained unit. A very clever design. It oscillates, but in a "two steps forward, one step back" sequence.

Was this a hand cranker? Turned a handle like the old manual drills, but the output motion was oscillating. For the one I have seen (may have in the garage) the connection to the valve was a metal piece with 2 prongs sticking out to engage holes in the valve head.

From hard won experience the ONLY way to get a lasting valve job is to use interference angle grinding- & also to strictly regulate contact area- the old way of lapping in using coarse then fine grinding paste went out the window when unleaded fuel was mandated in(leaded fuel had a lubricating, cushioning effect on valve contact surfaces)- to get reasonable life from valves/seats exotic steels were used in valves used on unleaded fuel- the old grind no longer works for long- whether you use a drill or twirl by hand(i have done both)- sure seems ok at 1st- but 20k km down the track- burnt valves. As against a proper interference fit grind of virtually unlimited mileage(assuming correct clearances etc).

You are correct.

Hand lapping went out a long time ago. Even the Old car engines that are being rebuilt today use professional angled seat surfaces and valve angles to ensure a proper seal. Mainly also going to harded seats (exhaust esp.) to allow the use of non-lead fuels.

Hand lapping was only a "fixit-up" technique used in the "bad old days". today it does not cost that much for a proper valve grind ( maybe a little more for 3 or 4 angle).

It was beaten into me as an apprentice that lapping of valves had to be done with a "reciprocating" motion in order to avoid scoring (continuous grooving).

My guess is that you can avoid this when using a drill by lifting the valve (bumping) at very short intervals and by reversing the drill quite regularly.

Very true, but the device does it all for you and are not expensive (far cheaper than doing the valves twice in 20K miles.....)

lapping is done with respect to foot size so heat transfer from valve to seat is not diminished, use prussian blue to check seat area and make sure to not provide any concentric rings by alternating direction and popping valve up frequently to disperse lapping abrasive, I did a merc mystique 16 valve engine after a shop put reman cyl head on with poor machining of valves, lack of sufficent margin caused two valves to burn, that's why I aquired the vehicle for pennies and with 70,000 miles on it, bought all 16 valves and seals with new head bolts, lapped the valves with the two compunds and alum oxide finish with the suction tipped handle, assembled head without springs to check cam bucket clearances and ground tip of stems to fit valve lash as needed, assembled with new timing belt and idler, tensioner, waterpump, runs like a dream, so will find out after few years if I did well, can't understand why car is unpopular but then again am own mechanic so I can precog failures and work around engineering failures..
all aluminum heads now use stellite seats and are to support unleaded fuel and lean conditions, but new computers prevent detonation or other problems running the yak piss we get at the pumps now, God I like Diesels

sinc
Ex Peugeot mechanic

Peter, I am still refacing valve seats with rose-cutters to the correct width and do the grinding with a dril , its OK and much easyer.

After I fitted the valve springs, I turn the head on its side, pour petrol in at the ports to see if the valves are leaking.

good i hpe it works out i cant see why it wont, i used the drill method for years with no problems just be light and keep the valves moving in and out to move the paste about.