The Ford Barn

Ian Curtis · 01-15-2023, 02:30 AM

I pulled the head looking for the source of a large cloud of steam on my '29 pickup. I found a crack in the head, so nice to have some resolution there. But that's not what I'm asking about. While the head was off I noticed lots of pitting in the combustion chamber of #4. There is some pitting in #2, and very little in #1/#3. The current pistons have no damage. See picture at the bottom of this post (pitting to the left of the hand)

I assume what caused this pitting is engine knock (detonation) at some point in the past? If that's the case, why is one cylinder so much worse than the others? I would think if you had something that made one cylinder knock (too much compression, wacky timing) they'd all knock and so you'd expect similar damage in all cylinders?

Kurt in NJ · 01-15-2023, 02:43 AM

A block I have that looks like that had cracks in the valve seats near the cylinder bore , long term slight coolant leakage, sitting without spark plugs can also cause rust pitting

Synchro909 · 01-15-2023, 04:22 AM

To back up what Kurt said, a friend of mine asked me to help when he bought a Model A that had been parked for many years. The compressions weren't good and we decided it was the valves. He took the opportunity to replace the original style valves with modern ones and the cam followers etc at the same time. We left the engine in the car and removed the head. I noticed pitting just like that in number 3. I pulled the cam out, replaced the followers and guides, ground the valves and reassembled. When we started it, it ran well enough but he noticed a day or two later that the coolant level was down and there was water in the oil. Long story short, we found that the head was cracked (uncommon in a Model A_) at number 3. Clearly, it had been wet in there for the time it was parked (probably why it was parked), slowly rusting away. I had a spare head which I had checked for flat, we fitted it and away he goes - pitting and all.

Ramman · 01-15-2023, 10:29 AM

Ian, where in the head was your crack that was the source of your coolant leak? Perhaps into #4 chamber?

Gary WA · 01-15-2023, 12:12 PM

That picture shows the block had been sitting with water in it for very long period of time prior to being put back together.

Ian Curtis · 01-15-2023, 12:58 PM

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Quote:

Originally Posted by Ramman

Ian, where in the head was your crack that was the source of your coolant leak? Perhaps into #4 chamber?

No, the head is cracked between 2 & 3. This was covered in a healthy layer of carbon when I pulled the head so I assume this happened sometime in the distant past.

Quote:

Originally Posted by Gary WA

That picture shows the block had been sitting with water in it for very long period of time prior to being put back together.

Okay, thanks! Does the pitting you get from detonation look different than this corrosion pitting? Or does it rarely get that far because you really need a lot of knock to actually start doing damage?

CWPASADENA · 01-15-2023, 01:19 PM

[QUOTE=Ian Curtis;Okay, thanks! Does the pitting you get from detonation look different than this corrosion pitting? Or does it rarely get that far because you really need a lot of knock to actually start doing damage?[/QUOTE]

Detonation will attack the aluminum pistons long before you will see evidence of it on the cast iron surfaces of the block or head.

As stated by others, it appears that the pitting is due to water in the combustion chamber, possibly from a prior leaking head gasket.

My opinion,

Chris W.

Richard Knight · 01-15-2023, 05:58 PM

I don't think detonation would affect the iron head or block. I would suggest that engine sat for a very long time in a damp environment with the exhaust valve open. Evrytime I see that kind of corrosion I think water us involved either due to a crack or poor storage.

Gary WA · 01-17-2023, 11:33 AM

Quote:

Originally Posted by Richard Knight

I don't think detonation would affect the iron head or block. I would suggest that engine sat for a very long time in a damp environment with the exhaust valve open. Evrytime I see that kind of corrosion I think water us involved either due to a crack or poor storage.

Agree with you for sure!!

01-15-2023, 12:12 PM	#5
Gary WA Senior Member Join Date: May 2010 Location: Clinton,WA/Whidbey Island Posts: 4,105	Re: Combustion Chamber Pitting That picture shows the block had been sitting with water in it for very long period of time prior to being put back together. __________________ www.whidbeymodelaclub.com

01-15-2023, 01:19 PM	#7
CWPASADENA Senior Member Join Date: May 2010 Location: PASADENA, CA Posts: 1,885	Re: Combustion Chamber Pitting [QUOTE=Ian Curtis;Okay, thanks! Does the pitting you get from detonation look different than this corrosion pitting? Or does it rarely get that far because you really need a lot of knock to actually start doing damage?[/QUOTE] Detonation will attack the aluminum pistons long before you will see evidence of it on the cast iron surfaces of the block or head. As stated by others, it appears that the pitting is due to water in the combustion chamber, possibly from a prior leaking head gasket. My opinion, Chris W. Last edited by CWPASADENA; 01-15-2023 at 01:20 PM. Reason: CLARIFICATION

01-15-2023, 05:58 PM	#8
Richard Knight Senior Member Join Date: Mar 2021 Posts: 130	Re: Combustion Chamber Pitting I don't think detonation would affect the iron head or block. I would suggest that engine sat for a very long time in a damp environment with the exhaust valve open. Evrytime I see that kind of corrosion I think water us involved either due to a crack or poor storage.

01-15-2023, 02:30 AM	#1
Ian Curtis Senior Member Join Date: Jul 2014 Location: Snohomish, WA Posts: 100	Combustion Chamber Pitting I pulled the head looking for the source of a large cloud of steam on my '29 pickup. I found a crack in the head, so nice to have some resolution there. But that's not what I'm asking about. While the head was off I noticed lots of pitting in the combustion chamber of #4. There is some pitting in #2, and very little in #1/#3. The current pistons have no damage. See picture at the bottom of this post (pitting to the left of the hand) I assume what caused this pitting is engine knock (detonation) at some point in the past? If that's the case, why is one cylinder so much worse than the others? I would think if you had something that made one cylinder knock (too much compression, wacky timing) they'd all knock and so you'd expect similar damage in all cylinders? __________________ "It is much easier to call someone else a genius than admit to yourself that you are lazy." - Dave Gingery

01-15-2023, 02:43 AM	#2
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: Combustion Chamber Pitting A block I have that looks like that had cracks in the valve seats near the cylinder bore , long term slight coolant leakage, sitting without spark plugs can also cause rust pitting

01-15-2023, 04:22 AM	#3
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 7,496	Re: Combustion Chamber Pitting To back up what Kurt said, a friend of mine asked me to help when he bought a Model A that had been parked for many years. The compressions weren't good and we decided it was the valves. He took the opportunity to replace the original style valves with modern ones and the cam followers etc at the same time. We left the engine in the car and removed the head. I noticed pitting just like that in number 3. I pulled the cam out, replaced the followers and guides, ground the valves and reassembled. When we started it, it ran well enough but he noticed a day or two later that the coolant level was down and there was water in the oil. Long story short, we found that the head was cracked (uncommon in a Model A_) at number 3. Clearly, it had been wet in there for the time it was parked (probably why it was parked), slowly rusting away. I had a spare head which I had checked for flat, we fitted it and away he goes - pitting and all. __________________ I'm part of the only ever generation with an analogue childhood and a digital adulthood.

01-15-2023, 10:29 AM	#4
Ramman Member Join Date: Oct 2022 Location: Findlay, Ohio Posts: 95	Re: Combustion Chamber Pitting Ian, where in the head was your crack that was the source of your coolant leak? Perhaps into #4 chamber?