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Flathead Engine Keyboard Warriors? Or Maybe I have some learnin' to do?


keithb7
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Recently I deleted a post I made in a Facebook flathead engine group. As you know, I like to share my project progress and enthusiasm for old Mopars. I believe it helps the hobby. Below here is the photo.  I was about to make some unfriendly rebuttal comments but chose not to. Here's the story.

 

I recently found a crack in the cylinder head, near the thermostat housing in my '38 Chrysler Royal. I pulled the head and I am swapping it out. My spare head is at the machine shop today getting crack tested, sandblasted and milled. While the head is off, for about 30 more mins of my time I can remove the manifolds. I'd test all valves for leakage. Indeed I found 5 leakers.  The previous owner of my Royal told me the engine was rebuilt about 8000 miles ago.  Not massive valve leaks, just allowing a little kerosene to pass through. A little kiss with some lapping compound was my planned job scope.

 

A statement on FB was made: "If you are that far into the engine and only doing valves, the engine won't handle the increased compression". One guy admitted that later after a valve grind he developed a knocking rod bearing. Maybe, on a high mile engine that you are patching up. Or the engine bearing was about to fail any day and it happened to after he did a valve grind. Other comments were made about the general misunderstanding about lapping compound. A guy went into a dialogue about people should not be attempting to fix valve leaks with lapping compound. That the grains in the compound will get deep seated into the valve seats and stay there, then cause the valve to continue wearing quicker.  "You should not/cannot lap hardened inserts", someone said. Further comments about the engine pushing oil past the rings after a valve seat clean up.

 

Keeping in mind this is only FB and there are subject matter experts behind every keyboard. I do trust and have confidence in the experiences shared here. I tend to skim past FB opinions, however maybe there is a learning opportunity here. I don't want to wander the planet ignorant. Deep down I was thinking, "Dude I hope you don't waste your money on a gym membership. You get plenty of exercise quickly jumping to conclusions."  Yet I kept my mouth shut. Lol.

 

My thoughts:

- My engine is not a high mile example. I'm just kissing the valve sealing surfaces to tiddle them up slightly. Removing hardened soot and or carbon build up.

- Yes I agree a high mile engine is likely to burn oil after a valve lap. Consider worn rings and tapered cylinder walls. Again, my engine is not a high miler.

- I do understand the use of lapping compound. To frost up the mating surfaces to closely inspect the seating area. Also A final sealing to get a nice tight seal.

- Lapping grains remaining in the surfaces to cause expedited valve seat wear. Really? I am having trouble accepting this theory.

- Yes indeed you can reseal hardened seats. I have done so in the past. Yes is takes a lot more effort by hand, but you can successfully hand grind and lap-in exhaust valves.

 

A general question about machine shop valve grinding. When I recently rebuilt my 1938 Plymouth engine I had the machine shop perform a valve grind. I provided them with a full set of new, single cut 45 degree stock valves. I asked them if they hand lapped valves for final sealing I was told no. I did not inquire as to why. I just assumed I would have to do the final sealing myself, and did so later.  Is it expected that when a machine shop does a proper valve grind, they achieve a 100% seal? I am doubtful. I did have to seal up my new valves in the newly machined block when I got it home.

 

Learning as I go here.... Thanks.

 

Leakers.jpeg

Edited by keithb7
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12 minutes ago, keithb7 said:

Recently I deleted a post I made in a Facebook flathead engine group. As you know, I like to share my project progress and enthusiasm for old Mopars. I believe it helps the hobby. Below here is the photo.  I was about to make some unfriendly rebuttal comments but chose not to. Here's the story.

 

I recently found a crack in the cylinder head, near the thermostat housing in my '38 Chrysler Royal. I pulled the head and I am swapping it out. My spare head is at the machine shop today getting crack tested, sandblasted and milled. While the head is off, for about 30 more mins of my time I can remove the manifolds. I'd test all valves for leakage. Indeed I found 5 leakers.  The previous owner of my Royal told me the engine was rebuilt about 8000 miles ago.  Not massive valve leaks, just allowing a little kerosene to pass through. A little kiss with some lapping compound was my planned job scope.

 

A statement on FB was made: "If you are that far into the engine and only doing valves, the engine won't handle the increased compression". One guy admitted that later after a valve grind he developed a knocking rod bearing.  I can understand that on a high mile engine that you are patching up. Other comments were made about the general misunderstanding about lapping compound. A guy went into a dialogue about people should not be attempting to fix valve leaks with lapping compound. That the grains in the compound will get deep seated into the valve seats and stay there, then cause the valve to continue wearing quicker.  "You should not/cannot lap hardened inserts", someone said. Further comments about the engine pushing oil past the rings after a valve seat clean up.

 

Keeping in mind this is only FB and there are subject matter experts behind every keyboard. I do trust and have confidence in the experiences shared here. I tend to skim past FB opinions, however maybe there is a learning opportunity here. I don't want to wander the planet ignorant. Deep down I was thinking, "Dude I hope you don't waste your money on a gym membership. You get plenty of exercise quickly jumping to conclusions."  Yet I kept my mouth shut. Lol.

 

My thoughts:

- My engine is not a high mile example. I'm just kissing the valve sealing surfaces to tiddle them up slightly. Removing hardened soot and or carbon build up.

- Yes I agree a high mile engine is likely to burn oil after a valve lap. Consider worn rings and tapered cylinder walls. Again, my engine is not a high miler.

- I do understand the use of lapping compound. To frost up the mating surfaces to closely inspect the seating area. Also A final sealing to get a nice tight seal.

- Lapping grains remaining in the surfaces to cause expedited valve seat wear. Really? I am having trouble accepting this theory.

- Yes indeed you can reseal hardened seats. I have done so in the past. Yes is takes a lot more effort by hand, but you can successfully hand grind and lap-in exhaust valves.

 

A general question about machine shop valve grinding. When I recently rebuilt my 1938 Plymouth engine I had the machine shop perform a valve grind. I provided them with a full set of new, single cut 45 degree stock valves. I asked them if they hand lapped valves for final sealing I was told no. I did not inquire as to why. I just assumed I would have to do the final sealing myself, and did so later.  Is it expected that when a machine shop does a proper valve grind, they achieve a 100% seal? I am doubtful. I did have to seal up my new valves in the newly machined block when I got it home.

 

Learning as I go here.... Thanks.

 

Leakers.jpeg

Yeah, I stayed quiet on that one with raised eyebrow.  It wouldn't increase compression any more than it was originally.  Start it knocking..sheesh.  Only thing with me I was trying for a piston to deck measurement freebie to see variations.  😁  Nothing is more enjoyable than adding work to someone else's tasks. 😂

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Posted (edited)

@BryanI will set my magnetic base dial gauge on the block and get you precise measurements today! I will report back soon. 

Edited by keithb7
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I think your instincts are correct.

They wouldn’t make lapping compound if it wasn’t useful.

My only complaint is you only get two grades corse and fine. The fine isn’t fine enough to suit me but I use it anyway.

I once worked with an Italian guy (he worked on Fiats and Lancias) when he did a valve job, he’d lap the valves and if they wouldn’t seat he sent the head out to have a new seat installed. The logic being that as the seat is ground it retracts the valve dropping the compression ratio. Okay.

I can see the importance of that in diesel engines for sure.

Not as bizarre as a 20 minute VW valve job through.

Drop the engine, torque the heads (to check for bad threads in the case) remove the heads, put a rag on the bench under the exhaust valve, hold a deep socket over the spring retainer and smack it with a hammer releasing the keepers. Toss the exhaust valve, slip in a new valve, replace spring, keepers the tap with hammer. Re-assemble. Done.

I saw it and it worked very well indeed, much to my surprise.

It was my boss who did it too. He claimed he could do a valve job in half an hour...I watched and he did it in 20 minutes!

Smoked two cigarettes and answered the phone once all in 20 minutes as well.

 

What am saying is if those guys can get away with this kind of stuff, I wouldn’t worry or listen to anybody else.

The valves seal with compression pressure. The valve springs only keep them in contact with the lifter. The proof I offer are the engines with desmodromic valve systems. One cam lobe opens the valve and another closes it, with no springs. The clearance is measured on both therefore compression pressure is required to fully seat the valve.

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I tend to keep my mouth shut (most of the time) on things I do not know about.  I am still learning flatheads, so I do not post much and instead, try to listen.  With that, what do these people think valve lapping compound is for, along with the fact  it is outlined in the manual?  I have never personally lapped valves, but your situation is the perfect scenario for it- addressing minor issue of valve not sealing perfectly.  
 

I have 2 FB accounts.  I might check them 1 to 2 times per year and never post.  I do not necessarily care what people have to say, and would rather use a site like this with a great knowledge base to pick people’s brains.

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4 hours ago, keithb7 said:

Yet I kept my mouth shut. Lol.

 

A skill set I have yet to master.  You are a better man than I.

 

I'd be real skeptical of any valve job that didn't lap them. 

 

As for engines failing after a valve job.  No kidding?  An engine wore out to the point it needs a valve job is magically going to have a bottom end with no issues?  SMH

 

Loren, Goodson offers valve lapping compound in many grits, you can choose your poison. 

 

https://goodson.com/products/lapping-compound?_pos=1&_sid=fad83fde1&_ss=r

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My take on lapping is that it is a good tool to prove that a new or reground valve makes good contact with it mating seat.  As a tool to make new seating surface, it is a poor one.  Seats need to meet the valve in a specific location and be of a specific width.  Neither of those can be reliably accomplished with compound alone.

 

That said, I've done it when lapping was the only tool available due to time or cost  constraints.  I've also used hand seat cutters, but not on hardened seat, for those I used to have a hand tool that used emery flaps in a holder to sort of refinish them.  Mostly  done on small engines that I didn't have correct stones to grind.

 

I grind seats, not cut as I don't have the tooling to cut seats accurately.   Shops that do have real head/valve machines can cut them so accurately that lapping is probably unnecessary, especially with new valves.  However I also put new valves in the refacing machine, just to make sure they are concentric with stem.  Some new ones are not.

I advance the valve until it touched the stone, just barely, then stop and inspect it.  If there is a good pattern all around i'm done.  If not, it loosed the chuck, rotate the valve about 90 degrees and repeat.  That's to be sure that my chucking isn't the cause of the issue. 

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A sidestep back to your head crack Keith. Spooky but I am dealing with the same thing...have put about 500 miles on my rebuilt engine and also have developed a crack next to the thermostat. Mine probably the result of having two metals next to each other doing a few heat cycles causing the problem. Getting a crack test done on the rest of it before deciding what to do. If otherwise sound may drill and stitch it. Not that easy to find replacement parts now although I haven't looked too far from home yet. The braze in the picture was to build up the corroded boss to help the gasket seal sufficiently. Should have used a different option in hindsight. 20220710_072406.jpg.3390f8dd66b46464115257eadcef4f96.jpg

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I kept my fingers off the keyboard with that post on the Flat Heat FB page. Folks prove far too often what they don't know when they post anonymous things on the internet. These are 70 year old flat head engines, not state of the art Formula 1 engines.

Edited by rallyace
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