Broken valve

[dgrinnan]

I brought my 1947 back to life after not being started for over 20 years.  It would run but appeared to have a stuck valve.  I poured a variety of solvents into the cylinder and ran the engine  hoping the valve would free itself.   I got to a point where my patients ran out and I decided to bite the bullet and pull the head.  I would have been waiting a long time for the valve to heal itself. The head of the valve was broken completely off.  I have ordered a replacement valve.  It did give me a chance to take a peak inside the engine.  Despite the broken valve the interior of the engine looked very clean.  Fingers crossed, after replacing the valve I can get this thing running like a sowing machine.  

 

I still haven't been able to figure out why the valve would have broke.  

[kencombs]

I think some , maybe most, valves are made from two separate pieces of material.  The stem and head pieces are joined by a welding process before machining.   It is probable that on that particular valve something went wrong at that stage creating a part that was defective at that joint.  

 

In the best of cases the joint is not as strong as the rest of the part.   OHV engines sometimes suffer from valve to piston hits, and those can cause the valve to fracture at that same place.  Extreme, but does illustrate that point of weakness.

Edited October 17, 2022 by kencombs

[dgrinnan]

The valve weld makes since as to it being a week point but the flathead 6 is not an OHV engine.  No chance of an impact. 

[kencombs]

3 hours ago, dgrinnan said:

The valve weld makes since as to it being a week point but the flathead 6 is not an OHV engine.  No chance of an impact. 

That’s not what I said.  Just pointing out that that is a weak point.   Seldom happens but they can fail due to a weak joint not up to standard and repeated closing shocks.   Luckily 230 springs aren’t very strong.  

[Merle Coggins]

Is it an intake or exhaust valve? It's possible that someone put in a long reach spark plug, or compression tool that made contact with the valve and bent it. That could have lead to it breaking. 

[dgrinnan]

The exhaust. It will probably remain a mystery.   I am just glad I was able to locate a new valve and don't have to pull the entire engine for a complete valve job.

[DJ194950]

All of the sodium filled HD exhaust valves are made in two pieces as is required to fill the head of the valve with sodium for cooling purposes to make valve less likely to burn under heavy duty use for long periods.

 

All of the sodium filled valves that I have seen the tops of the valves are slightly domed to provide more space for the sodium.  Are all filled valves like this? That I cannot say as my limited experience is with the Mopar flatties and 1 International OHV 6 cyl. back in the 60's.

 

Often used in Heavy trucks and stationary use motors.

 

DJ

Edited October 17, 2022 by DJ194950
add info

[Los_Control]

1 minute ago, dgrinnan said:

The exhaust. It will probably remain a mystery. 

I agree with @kencombs theory.  While it is very uncommon it is a weak point. If something goes wrong in the process of creating the valve ... Life happens.

 

Last year on drag week Tom Baily hurt his engine .... Was end of the week & still able to drive the 5K+ horse power engine & baby it through the ceremonies on 7 cylinders.

When Steve Morris tore down the engine for inspection, the valve head had broken off & embedded itself into the piston.

Steve who builds many race engines .... He said he never seen a valve break like that, I think he was more impressed it did not destroy the engine.

 

My only point, it happens. People who build race engines will put it as one of the last things on the list that will break .... but they can.

[dgrinnan]

Yes, at this point I am relived it did not cause any damage and it is a simple repair/replacement.