Valve laping with power drill?

[36tudordeluxe]

Leak down test on my '36 LB indicates air getting past the valves, this is on engine with a little over 500 miles on it since rebuild.
Saw video of suction cup attached to hand held power drill that seemed to work very well, but others say it would be very easy to damage the valve and seat; what do you think?

[rotorwrench]

Lapping is generally done with constant rotational direction changes to prevent streaks around the seat or the valve. Rotating one direction for a half turn then reversing rotation for a half turn and so on while lifting the valve off the seat every couple of cycles is the normal way most folks do it. This keeps the lapping compound moving around so that the grit doesn't set in one place.

If a person just rotates one direction, it tends to put grinding streaks or light scores in the seat and/or valve face. In effect it would be grinding the surfaces instead of lapping them.

Seats can be ground with angle grinder wheels or cut with cutters to get the angle profile then the lapping will polish the seating surfaces to a finish that depends on the coarseness of the lapping compound. It is basically just to insure that the valve is seating all the way around.

[SofaKing]

I've done it that way, it can work but is not considered orthodox. Don't overheat things by applying too much pressure or staying in contact for long duration. I go slow speed, light, short touches a few seconds at a time. Check contact with Prussian blue when finished. The caution about introducing valve lapping paste into your fresh rebuild needs mentioning as does duplicating your test results so your not fixing the wrong thing.

[tubman]

I have an old "manual crank" valve lapping tool. You turn the crank and it goes half a revolution one way and then half a revolution the other way. It also retracts once a revolution. That's the motion you want, not strictly one way like a drill would give you. I wouldn't do it. Hand lapping is fine on a one cylinder Briggs & Stratton, but can get tedious on an eight cylinder. That being said, it's probably a better way to go..

[Ole Don]

If you lap, wipe out the crud with a wet paper towel, then heavy oil on the seat and the valve, then turn the valve by hand to see how well you did. There should be a nice even mark all the way around, on both seat and valve. Then, double check clearance.

[Mart]

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I'm surprised you have valve seating problems at 500 miles. Are the gaps ok?

Mart.

[36tudordeluxe]

The consensus seems to be to re-lap the old fashioned way and thats what I'll do.
Am surprised that I have valve problems also but leak down test says that I do.
After pulling heads today I found these deposits in the water way passages, something I haven't seen before. I'm using a product called No-Rosion (aluminum heads) and a water wetter, is this why I'm seeing these deposits?

[cas3]

i have better luck with a black felt marker pen then the blue stuff, easier to see i think. also, i mark the valve and the seat in 4 spots, then lap, and then look at the contact marks in the black pen marks

[Ronnie]

What is the history on the valve job.Who did it and how

R

[flatjack9]

I've never used No-rosion,but I wouldn't be happy with my cooling system looking like that.

[36tudordeluxe]

This valve job was done by a machine shop over 25 years ago but the engine only has around 500 miles or so on it. Here's a better picture of the deposits in the block and heads.

[Mart]

Jeez is that supposed to be better than just normal (distilled) water and a good quality anti-freeze/summer coolant?

Factories don't fit the normal stuff to millions of vehicles worldwide for no reason.

Mart.

[Karl Wolf]

A good valve job does not need to include lapping.

Only MAYBE to show where on the valve the seat is.

I agree with someone elses idea of using black felt tip marker.
Better than lapping. Worked for me.

What tooling was used for the valve seats and grinding the valves?

How were the valve clearances?

Karl

[FlatheadTed]

It looks like you had copper gaskets with a Aluminium head that sets up a electrolyse action ,you also may have had a light film of rust on the valve seat after 25 years ,Ted

[Kurt in NJ]

Aluminum heads?, I have seen such corrosion on ones that have sat long times

[36tudordeluxe]

Yes, aluminum heads, copper gaskets after approx. one year.
Going to try the black marker pen, am I looking for the marks to disappear completely on the seats and valve bottoms?

[Ronnie]

Originally Posted by Karl Wolf

A good valve job does not need to include lapping.

Only MAYBE to show where on the valve the seat is.

I agree with someone elses idea of using black felt tip marker.
Better than lapping. Worked for me.

What tooling was used for the valve seats and grinding the valves?

How were the valve clearances?

Karl

Yup x2!!! ^^^^ 25 years ago "yikes" maybe a poor job at best. Lapping only really shows where the seat is in regards to the valve face,and the width also.

R

[Ronnie]

https://www.google.ca/search?hl=en-C...pe=&as_rights=

Some info here that will get you going.

R

[rotorwrench]

Check closely to see if you have any bent valves. It's not common to have bent valves on a flathead V8 but lots of things can happen in 25 years. If the heads show no signs of contact in the pockets then they should be OK unless some were already bent the last time they went in. Also see if there are any loose seats in the block. If someone didn't get a good interference fit upon replacement, they can come loose. I've also seen those old seats start to crumble if they get too much corrosion going on.

[Kurt in NJ]

Since you did a leakdown test you sould know which valves are problems, most likely if it just had the seats cut, valves refaced 500 miles ago the most likely cause of leakage is the valves and or the seats are not concentric, something lapping won't fix

when you remove the valves take pictures of the valve, seat that have leakage and post