Valve lapping...

[Lee_in_KC]

When I went through high school auto shop in 1965, one of the things they taught us was valve lapping. Do they still do that? I haven't seen it on any of the current hot rod TV shows.

 

[rooster57]

I havent seen anyone lap valve seats since highschool. But if your guides were good and all the seats sealed then lapping would clean and enhance the seating and correct minor leaking.

 

[Screaming Metal]

OOOOOh YYYYYea........old school.......it works. Yes, its very much still done these days.
Most of the stuff done today is with cutters, get it really close then touch it with a grinding stone to get it really, really close. Pop your valve down hard to see where the seats landing....do your top cut and undercuts to bring your seat width in.........then lap it on in......

They've got Nu-Way cutting setups...................suppossed to be quicker and better.......in some ways it is.......I like getting the perfect seal.......

 

[Francis Blake]

I was watching a car show a few days ago and they were building a hot engine , the builder said there is no substitute for lapping the valves. That is what I allways do, counted up the engines I have built comes to 35 lucky I guess didn't have a bad one in the bunch...:lol:...Francis

 

[Ted Brown]

I know that when we do a drag engine's heads, the seat is about the width of a dime, a street cars is a fat nickel, and yes they were always lappen in to a perfect mating surface... Of course the race cars had the heads off all the time, it seemed. :sofnny:

 

[Screaming Metal]

I was watching a car show a few days ago and they were building a hot engine , the builder said there is no substitute for lapping the valves. That is what I allways do, counted up the engines I have built comes to 35 lucky I guess didn't have a bad one in the bunch......Francis

Yes, when you fire a engine for the first time....its best to have all your valves seating. I always lap them in....only way to be sure....then I vaccuum test them. That way you know they're perfect without putting them on the engine and wasting a head gasket. You can pick these up at Goodson's Engine Building Supplies up north......kinda expensive for the weekend warrior...but if your serious...its the only way to go. Folks at Goodsons are great folks and will go outta their way to help. They've been helping engine builders since about 1945..........
Another way is to make like a plate for the intake and for the exhaust and put a air fitting on it so you can put about 25 lbs. of air pressure (please use a regulator!) to it.....and then spray a soapy solution on your valves to see if they leak.
The old garage mechanics would just stick a airblower in the port runner with a rag stuffed around it, while they sprayed a soapy solution in the combustion chamber.......quick, easy, and inexsensive........but a pain in the ass alot of the time.

 

[jjsticks]

I still lap the valves at work when i building the heads.I don't know any different!

 

[Keeper]

I still do this when I do any head work (which is rare) Whats even more fun is going to the parts store and asking for "Valve lapping compound" The looks you usually get are pretty funny.

 

[jjsticks]

or that blue stuff.perusin blue?

 

[estesken]

When I went through high school auto shop in 1965, one of the things they taught us was valve lapping. Do they still do that? I haven't seen it on any of the current hot rod TV shows.

Hi Lee I won't speak for all tech schools just mine. Yes lapping works and is ok if cleaned up properly. I do show students how to lap valves as a demo but only so they can see seat and valve contact. A interference angle should make it seat. Our local machinist recommends not to because some do not clean abrasive well enough. Right or wrong I do not spend much time teaching much rebuilding technique. How to Torque, seal, and most important diagnose. With 175 days or 1080 hrs there isnt enough time to make them machinist too. Nearly half of our program is spent on Electricity and Engine performance ( and not the kind of performance you guys think about.) Engine Repair is what the student expect when they take the class and is part of my dilemma. I need a better balance between having fun with cars and making them marketable when graduate. Ill be looking you KC fellows up over the summer to get some ideas for next falls planed bucket build.

 

[Screaming Metal]

Hey JJ....I use dykem, brush or spray........persian bluing is really expensive, and also too thick. PB is made for machinists and toolmakers that have a shaft or bushing with a highspot.....it'll put the bluing onto the mating part that hits it. The Dykem will leave a really thin line when it is hit by the valve on the seat.....I use my PB only on special occassions.......like setting up the ring to pinion clearances, rebuilding the blowers and looking at wear patterns after we've just setup and installed a rear in a FC...........

 

[Therealkoop]

I just recently graduated from a school for high performance automotive and engine building. We lap everything, even when using the fancy billion dollar automatic seat cutting equipment.

 

[Screaming Metal]

I just recently graduated from a school for high performance automotive and engine building. We lap everything, even when using the fancy billion dollar automatic seat cutting equipment.

There ya go! Better to be safe than sorry ......at least you know they're sealing.....

 

[Ted Brown]

It is very hard to beat good old hand work, machines can do soo much these days, I just hope the hand work does not fall by the wayside, if it does, no more custom cars with that just right look...

 

[Wild Mango]

Valves, especially the exhaust, get rid of heat two ways, stem to guide and valve head to seat. If the valve is making good contact all round with the seat it maximises the area for heat conduction. If the valve leaks at the seat the hot gas blasting past will eventually erode the metal on both components. So, lapping is good lots of ways..............................