Testing has revealed that my 67 big block (casting number 3904351) has a crack in the lifter gallery. Probably the result of a piston rod striking the area sometime long ago. The block pressure tests ok. My engine builder says that he would cover the area with epoxy and cement and would warranty the engine against failure in this area. How concerned should I be about this development and what other procedures might be followed to prevent a future problem with this crack?
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Re: 67 block crack
John-----
The engine builder is probably correct. I think that the epoxy repair likely would work just fine. Also, it's the least "aggressive" sort of repair. If it doesn't work, then you caould always resort to a more "aggressive" repair in the future.
The only other repair method that I could recommend to you would be "pinning" the block. This involves the drilling and tapping of a hole at the end of the crack and installing a special, tapered, threaded "pin". Then, successive holes are drilled and tapped along the crack line and additional pins installed, each overlapping the previous pin. In this manner, the pins are "interlocked". This process continues until the entire crack line has been "pinned". This work must be done by a professional experienced in this sort of repair. Also, it's expensive since a lot of time is involved.
Actually, I would not employ the above-referenced method now. I'd go with the epoxy repair. The above-referenced would be the "next step" if the epoxy doesn't work. I think that it will, though.In Appreciation of John Hinckley -
Re: 67 block crack
Hi Joe,
Why can't the block just be braised or welded? I had a 327 Corvette engine
many years ago that I got for free because it had half-moon shaped cracks.
One above each motor mount location on the block. I guess someone forgot
to add anti-freeze. Anyway, I took the short block ( pistons, rods & crank
assembled ) to a local "blacksmith shop". They braized the block on each
side and I ran it for several years that way with no leaks. Was I just lucky?
Why wouldn't this solution work here?
SteveComment
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Re: 67 block crack
Steve-----
Brazing would work but I don't think that it would work any better than the epoxy. Plus, it's "one step up" on the "aggressivity index" from the epoxy repair. Brazing will seal the crack but it's not going to add very much strength. An epoxy like JB Weld will do about the same with no need to heat the block, so why braze?
Personally, I don't recommend welding for a block. Using high nickel welding rod, an effective repair can be performed. However, welding can change the metal structure of the gray cast iron surrounding the weld. Then, new cracks can appear. I just don't like trying to weld gray cast iron, but it's ok for low strength applications.In Appreciation of John HinckleyComment
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Re: 67 block crack
Joe, Thanks for your thoughts on this repair. The first questiion I asked was could the crack be welded. The crack is in a difficult location and the opinion was that welding would probably weaken the cast iron structure and possibly lead to more cracks and a bigger problem. I guess the major concern is sealing the crack. It is not close to any of the cylinders. It just seems to me that the constant heating and cooling of the block will aggravate the defect.Comment
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Re: 67 block crack
I would do one additional thing prior to epoxy.
Drill a small hole at each end of the crack intersecting with the crack at least a small amount. Pin these holes if desired.
This will provide a stress reducer and help reduce probablility of the crack growing.
After drilling (and pinning if desired) epoxy to seal the crack.
Welding cast iron can be successful if you find a shop with the equipment and experience. A few shops around the country make a business of welding large farm tractor cast iron parts. They have large ovens for thorough heating of the whole part, experienced welders and controlled cooling process.
Something like an engine block may need major remachining after such a traumatic process.
VerleComment
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Re: 67 block crack
just yesterday, i tried to weld a crack in an old cast iron apple butter kettle with nickel rod. I now have many cracks alongside of the repaired crack. the kettle will become a flower pot for the misses. mikeComment
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Re: 67 block crack
to weld cast iron you must heat the object it a gas fired pit to get it all up to temp. there is a outfit in new york that does it. i have seen 2 SBC blocks they welded together to make a V-16Comment
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Re: It's tough
I agree with Joe, Epoxy it and keep an eye on it. I'll wager that it's the last you will hear from it.
Welding cast is next to impossible for the garage/shop not geared to do this type of work.
I remember my father welding a truck block with a hugh split and prior to welding after he preped it, heated the whole side of the block with a hugh torch and comtinued to heat the block (my job) while he performed the weld. It worked, but it took time, lots of acetelene/oxygen and know how.
I have always been a proponent to drill out crack ends to stop cracks from transmitting further.
Epoxy and wire dril sized holes? sounds good to me but then again, it's not my block either.
Your call John,
ChuckComment
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