VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Heads Again

Hey 4 cyl fans.
My cracked cylinder head woes continue ,but there might be light at the end of the tunnel.
I have found another 4 heads, some on engines and others not, however they are all cracked in the exhaust port, up the back face and across the roof. A couple are cracked outside over the top of the head also.
We sacrificed one and cut it fair in half, through the port, to see just what was there to work with. What a pleasant surprise; indeed a very clever piece of casting showing remarkably even wall thickness (4-5mm) and no dags or roughness in the gas flow areas at all. A far cry from modern stuff I have seen.
The iron is beautiful to weld and braze, so we are going to have a go at repairing a few heads with more accessible cracks. The bronze probably won't tolerate the heat so we have come across a cast iron spray-weld method that uses a gas torch with attachments and very expensive welding powder. The test weld came out superbly and as the metal deposited is a little softer than the base metal it should flex with any tendancy to crack again.Of course the crack will be machined out before welding, but we are considering strengthening the whole crack zone by covering it with 1-2mm of weld. But would this extra thickness cause further uneven hot spots and more cracking?
How about installing a thin stainless plate bent to an angle to sit against the cracking surfaces to deflect some of the heat? Any thoughts anyone?
As we progress I will try and get effective photos to post because I'm sure you will all face the same drama at some stage.
Cheers for now.
Geoff. :confused:

Hi Geoff,
To find an early single port head that isn't cracked is a fairly rare thing.It sounds like your spray welding idea is a good way to go,as long as the metal you're spraying has the same rate of expansion and contraction as the cast iron in the head.
Otherwise it may crack again.The only other alternative may be cast iron fusion welding,using oxy gear,cast iron filler rods and the proper flux.I've just repaired a water pump
housing and exhaust manifold for a mate's '27
Olds,and it came out just fine.
The stainless heat deflector plate may possibly work,but as long as the water passages in the head are as clean as possible,and your radiator and the rest of the cooling system are
clean,then you should have no problems.

:)

Thank you CJP.
I too am coming to the same conclusion; that non-cracked heads are a thing of fantasy.
I have had my 25 for nearly 40 years so have done well to get this far before the dreaded leaks appeared. But as I have said previously, all the old timers warned me - Chev Fours crack heads...
Peculiarly, if it is such a widespread problem, one never hears talk, or sees articles on repairing the blighters. Is everyone else also just hoping that it won,t happen, because I have not had a reply from anyone who has "been there and done it"
I could always try a warranty claim!
Cheers,
Geoff.

Geoff
28 heads don't seem to crack and most people who can't find a good single port head fit a 28.
There are two reasons for the cracking, the single port generates a lot of heat and the insides of the head are eaten away by rust over the 80 odd years that they've been around.
There might be a market for getting new ones cast
Chris

Hey Chris,
There must have been a market in the 30's also because in my collection I have two Australian non-genuine heads. But alas, despite being from different manufacturers and a bit more robust,they too have cracked.
Talking to a Sydney parts dealer this week,who used to specialise in Chev Fours post WWII, he said even back then they were lucky to find one in two not cracked, and by the early 60's it was one in four or less.It must have been a problem finding enough good ones, because as late as 1958 there were were still 65,000 Chev Fours still registered on Aust roads (according to a newspaper article I have on the around Aust. Redex Trial of that year in which a '28. was entered).
This bloke also confirmed your comment in that 28's do not suffer the same ills.He used to race and thrash them mercilessly without problems other than a crack that would sometimes appear next to one of the water jacket holes, but was easily fixed.
Blimey, they must have sold a lot of cars originally if 68K were still in use more than 30 years later.
I wonder how many of us would be interested in a new one being made? It can be surprisingly cheap getting castings done now with some of the new techniques and alloys.Machining would likely be the biggest cost.
Geoff :)

Geoff
There is no way there are 65,000 Chev 4's still in use in Australia, in fact there weren't that many Chev 4's sold new in Australia. I doubt even there would even be that many in the world. I don't have the exact figures but can get them if you want.
I'd reckon there would be somewhere between 1000 and 2000 still on the road, but that's just a quess from over 30 years involved in Chev 4's
PS I can supply a 28 head and the appropriate manifolds.
Chris

Hey Chris,
Funny you and I chatting to each other in the same country via the US.
Yes 65K cars in use does sound exagerated for 1958, but that is the press.
Total national sales for the 20,s would have been that without much trouble, but it's all a bit academic now.
For someone to gear up back then to make replacement heads would also indicate the potential for robust sales, after all they would also be competing with the genuine item from GMH.
Anyway we are pressing on with our repairs at this stage because it looks promising from the test welds we have done. It's all happening this week.
The first we are doing is the one off my 25 because the crack whilst big enough to walk through is fair square in front of the port opening and easily accessed. It also has excellent seats.
The other two are the Australian jobs which also have good seats and only fine cracks. They are the squared off later style head which my mate here can use for his '27. All the other Chev jobs we have are well worn in the seats, require inserts, or have cracked off to the side of the port and will be awkward to get at.
Thanks for the 28 head offer, I may yet have to take you up on it if our resurrection efforts with a $200 bottle of weld powder do not succeed.
Will keep you posted.
Cheers Again.
Geoff