[XNTRCI-T]

When I went through high-school auto shop in the mid-60s, we were taught to hand-lap valves. Is that still done?

[NEW INTERIORS]

That's the only way I ever did it..

[eloc431962]

Thats how i do it . Cole

[cobalt327]

Oh, but you'll get the grinding compound embedded into the seat!!!

LOL- I always "hand" lap- but I cheat w/a reversible drill.

Tried using an old wood drill (hand cranked) but found that to be awkward as heck- I'd sooner do it be hand, even w/o a rev. drill.

Only thing to using the elec. drill, is to not run for any legnth of time- just bump it a couple times, check the pattern in the dycum, reverse it, resmear the compound (I always just use "fine"), bump a couple times, etc. so as to not groove the seat/valve.

[XNTRCI-T]

I'll hafta look on the intarwebz for a pitchure, but when we did it, we had a wooden spool with a suction cup on the end, and you sucked that cup to the valve and spun it between your two hands. Very stone age...

[cobalt327]

Originally Posted by XNTRCI-T

Very stone age...

Yep!

But fun to use as a "throwing stick" (instead of a knife).

[cliff tate]

i still do it just a bit to be sure the seat is where i want it. could use blueing but it is messy . cliff

[fast68]

what does lapping do anyways ? do learn me

i have seen this kind of tool in the past and knew it was for valve work of some sort and i have heard of valve lapping commonly.

this is one thing i dont do.. replace valves...

i always take heads to a shop for this kind of work.

the most i will do is replace stem seals and springs.



thanks!

[cobalt327]

Originally Posted by cliff tate

i still do it just a bit to be sure the seat is where i want it. could use blueing but it is messy . cliff

Especially the don-drying paste.

What I found years ago was a pint of alcohol-based blue that dries quickly, but won't rub off by hand or smear everywhere. It'll stain your fingers if you're not careful and God help you if you spill a lot of it, but applied w/a cotton swab onto the seat and valve, the stuff works good.

[Deez]

Most good guys using the new equipment cutters do not lap, some do if only to check their work - might be like OCD. Do not think lapping your valves is anything like a VJ. If the heads have big miles etc you will be better off just having them done and not worry about lapping. Stone Age or old school, either way it's not up to speed in today's VJ world. This is not to say one who is proficient and experienced cannot do an old school VJ. It just depends on where you are with any of that. Hope this helps.

[cobalt327]

Originally Posted by Deez

do if only to check their work

I don't have a Serdi, but I do check the work by lapping when heads are returned from the shop.

There might be tools that do that as well, but lapping works fine for me.

[Deez]

Sure right. I'm jus not confident most would lap properly. If the VJ is good and you lap too much or with too abrasive a compound you may screw up the VJ. This being someone unfamiliar with lapping of course. The methods used, mix or match, doesn't matter so long as everything is good in the end. I'm sure there are some good head guys that could chime in

[cobalt327]

Originally Posted by fast68

what does lapping do anyways ?

It mates the two surfaces, and will show you the relative position of the seat.

It won't take the place of a valve job and doesn't show the concentricity of the seat. It will show that the mating surfaces are compatible, and if there's been anything missed by the stone or cutter.

It's redundant for the most part. But for the hour it takes, it's cheap peace of mind, IMO.

[1pistol]

I do my heads myself and I finish up by lapping.I did this even when I used to send my heads out.It mates the two surfaces.I dont care what kind of machine you use.When you do the valves it is seperate from the hard seat process and the two need to be mated.Deez dont worry about messing up the valve job you would have to lap a paticular valve and seat for a long time to do that.If the the seat and valve have just come off the machine it does not take that long to lap them in.

[4 Jaw Chuck]

Originally Posted by cobalt327

doesn't show the concentricity of the seat. It's redundant for the most part. But for the hour it takes, it's cheap peace of mind, IMO.

Redundant? Doesn't show concentricity?

Holy moly Batman, hand lapping the valves is one of the most important parts of a valve job! How else can you check concentricity without an expensive seat dial indicator (which doesn't tell you exactly where the valve will sit). How else can you ensure the seat face and valve face have the proper 1/2 degree difference in angle?

The manufacturers don't do it because labor is expensive and eventually it will seat during normal use on a grocery getter but getting that perfect seal is important to power production, seat life and valve cooling if you want to run that engine hard.

If your doing it with a drill all your doing is grooving the seat and ruining everything you just spent your hard earned money trying to accomplish. Lapping valves use the same procedure as lapping an expensive telescope mirror except you can't do a figure eight pattern, rotate half turn in one direction, lift valve to redistribute compound and then rotate half turn in the other direction...repeat. When you can feel the compound losing its cutting ability you wipe off and replenish. Both faces should be a dull grey when your done with even width across both faces.

I test the seal by leaving the port full of gasoline overnight with the valve spring installed, a dry combustion face and full port the next day means its good. Most shops use a vacuum setup with leak down gauge because its faster and does the same thing more quickly.

Guy who are serious do it because the Gods live in the details and getting valves to seal is not guaranteed unless you check them by lapping. It needs to be air and liquid tight folks.