Technical Cracked Double Humb?

Hi there-
Has anybody experienced such a leak, or what it is, on an iron cylinder head?
After sitting in aprox three months after last drive, I lifted the cylinder heads, Double Humb 462, 1966, and found trace of water in no. 3 cylinder.
When looking in the exhaust channel, witch also is the crossover channel, it looked as water came from the middle of that channel, was running down to the exhaust valve, and then into the cylinder.
After now a year later, I made some compression plates, and checked with around 80psi, and up to 140psi, no leaks. Only from the plates I made.
I think they will go on again, they do not leak cold, and it looked as they where doing just that…
Iron manifold, square bore with 4jet carb.
No white smoke or water consumption noticed when driving.
Here’s some photos

 

Stop leak , cross your fingers or replace the head

 

Any way you slice it, that head is junk.

 

I found a replacement head with same casting no.
Needs rebuilding though.
But how can water under no, or low pressure run in that amount the rust trace shows, but not at 80 psi
even overnight????
For me it’s a mystery

 

One of the mysteries of the universe? LOL.

 

Looks like a circle were the leak starts from . Almost like it was pined or plugged/ repaired

 

Maybe, and this is pure backyard hack logic mind you, it's because when the engine is cold, the crack is closed, when the engine is at operating temp. it opens up. NOW for the really irrational thought, when the engine is running, the exhaust pressure keeps the coolant in the system where it belongs. When the engine is off and cooling, the crack is still open, and pressure from the cooling system forces coolant through the still open crack as it cools, because there's no exhaust pressure to force it back into the cooling system. Sounds ridiculous, I know, but just maybe...

 

One thing that was not mentioned is to ad liquid sodium acetate AKA water glass to the coolant system. That seeks out the leaks and seals cracked cast iron blocks and possibly heads in certain instances. It even says that on the bottles. I actually have seen this used and was skeptical at first but after witnessing the procedure I am a believer. If you look at the modern day manufacturer antifreeze , That is added in their blend of coolant.
Vic

 

Take both heads to a machine shop and have them magnafluxed, right now you know that there has been water present not where it came from.

 

I have seen similar situations in the diesel world on a number of occasions. The cylinder shows signs of coolant intrusion, but the head pressure checks just fine - at room temperature and off the engine, and the mag-flux guy can't find anything either. It is not until the engine is brought up to operating temp that the leak returns. The crack / casting flaw only opens when it is heated up and under operating stress. The image below is of a crack in the intake port of a International DT466 head. That engine had the exact same symptoms you are describing and the cylinder head passed both pressure test and magna-flux. It took us cutting the head up with a band saw and using dye penetrant to find the crack.



Working on a C15 CAT right now that is the exact opposite. It likes to blow bubbles into the cooling system, but only when it is cold, and only when the turbo is producing boost. Once it warms up, no more bubbles, and the bubbles are just air, no sign of combustion products being in the bubbles. Our best guess is the head has a small crack somewhere in the intake tract that seals up as the head heats up and expands, but we have been unable to locate it.

 

Heat. Metal expands and contracts, so temperature changes can make leaks show up.

 

Not to mention how the head is flexed when torqued down.

 

Thank you all!
Good thoughts, and bringing in experience as well.
I think I try heating the head, while under pressure.
And get the spare head rebuilded.
I appreciate all the explaining and positive inputs!

 

Lots of speculation in the replies here, but have you considered that it's just condensation from sitting for 3 months? Sure seems like a very small accumulation of moisture and not a continuous or repetitive leak.

 

As for now I will put the head back on, planning to monitor that cylinder with an endoscope reguarily, and in addition find a leak additive as Vics stuff sugested.
And right, it’s all just guessing, since I see only the traces of the water I think was there.
A good explanation is, that when shutting off the engine, cooling stops, but heat and pressure is present.
This forces water through the leak, which then closes again when cooling down.
Again, thanks for your thoughts.

 

Thanks for sharing your experiences, so good to have other eyes looking at a problem.

 

That water expands at a rate of 1700 to 1 at 212* . Stream is probably the cause of the leak seeping through the crack at this point.

 

I had a circle track engine that had a pair of ported Bowties on it. One of them was cracked, but it only leaked water when it sat during the week. I'd pull that plug, crank it over to blow the water out, reinstall the plug and go race.

I ran it that way for a long time until I got too nervous that the crack was going to open up while racing and hydrolock that cylinder.

Back in the 90s when I used hump heads on circle track engines it was common to buy cores that turned out to be cracked. They're twice as old now as they were then so I imagine it's gotten worse.

 

If it was mine, I'd pull BOTH heads and have TWO heads rebuilt (obviously substituting a different head for the one that may be cracked). It never makes sense to do a valve job on 1/2 of an engine (at least in my mind!).

 

I'd use it as an excuse to just buy some of those new aluminum aftermarket heads with a double hump on them and paint them red ...........or leave em shiny. The point is that you may waste a lot of money and still not know if they are good or bad. If you get them rebuilt and one is bad, what do you do then? Also, if its cracked you may end up ruining some other parts or the whole motor. Put that money toward the cost of the new heads and sell the old heads to someone who has a cracked head and just needs one head. You can probably get a good price for the single head from the guys that have to have original stuff......

 

If I had gone through the trouble of pulling a head for issues like this, it would never go back on without taking both heads to a machine shop to be magnafluxed and either repaired, or replaced. Just not worth possibly having it get worse, or having to do this again.
With the cost of a new or rebuilt good heads these days being not that expensive, just not worth it to me. I see new aluminum heads complete on Ebay for $625-$700 a pair, and my local machine shop sells fully rebuilt iron Chevy heads for $550 a pair. Worth the peace of mind and only one time putting the engine together for me.