At the last LeMons race, we blew another head gasket. Apparently it's still pinging a little even after recurving the dizzy, but that's a story for another thread. The important bit for this story is that for the first time ever, we blew into the water jacket rather than just between cylinders. Probably a result of using a different gasket (Victor Reinz instead of Fel-Pro) and ARP head studs with more torque than we'd previously used on the stock bolts. It actually blew in three different places, over a much longer period of time.

Anyway, pressurizing the water jacket apparently caused a small horizontal crack around 1" long on the driver's side of the block. It's in the area of the casting numbers. Does anyone have success stories from repairing cracks like this? I know that no matter how I repair it, I need to drill a hole on both ends to stop the crack from running further.

My initial thought was to grind an angled groove along the crack and braze it, but after looking into brazing I realize that's a much higher temperature process than I thought. It may not be as bad as welding, but there's still a lot of room to screw up with pre- and post-heating. I also don't own an oxy-acetylene rig.

I figure any type of epoxy is just going to fail again. What about solder? Would that be strong enough to hold up in the medium-long term? We've got a big damn aluminum radiator, so our coolant system normally runs unpressurized even when racing (~190 F). The crack doesn't even leak during normal running; we only saw it because it was blowing bubbles when the car came off the track with the temp gauge pegged at 250. But even if I ignore the crack itself, I'll have to fill up the drill-stop holes.

Another option I found in an old thread here was stitching. This sounds like a repair I'd have no problem performing. Doc posted this link to a company that makes specialty hardware for the process. It's supposed to be better than your typical old-school stitch repair due to the angle on the screw threads. Anyone ever done this? I plan to call them during the week, as their site is a little lacking in technical details or pricing.

Also, how thick is the casting in this location? After I get the manifolds off and locate the crack again, I'll post a picture.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Those stitch thread plugs work well if you can get to the crack easily. Also, I don't know if you know this or not, but any/every time you blow a head gasket, the blocks deck surface and head should be resurfaced or you'll keep having this same problem.

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There's no such thing as too much cam....only not enough engine!

what he said!

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1964 Dart GT

OK, I realize I'm going to talk about a Ford, but way back in the day, I had a 64 Fairlane 500 wagon, with a straight six in it. The day after I bought it, it dropped a rod and had to be rebuilt. I guess I should have paid more for the new motor, because shortly after installation it developed a crack in the external water jacket. I was VERY broke at the time, just outside the warranty period, and did not have a lot of options to get it fixed. So, I ground down the area on both sides of the crack plus an extra half-inch or so on each end. I mixed up a batch of JB Weld, and applied it liberally to seal up the crack. It worked like a champ. I drove that car with NO leaks whatsoever for several years till I moved it on to a new owner.

I'm not going to get too far behind this as a good idea, but it worked in the real world when other options were not possible.

Zach

I do not have experience with repairing cracked blocks. This is not a high stress area, I believe, so brazing or stitching or JB or other things might work for a while. I will defer to others on here with personal experience.

I would not worry much about the head gasket and surfaces, assuming you have fixed the (probable) detonation issue. Get a WB O2 on that thing and seal up the exh leaks, then you can tune mixture. The lean mix and hot/long plugs probably were killing you. On one Slants where I observed a head gasket blow (one of them LeMons E30/6 car, flipped water pump belt and 2 laps with no water), we put a gasket on it and ran another 2 whole races and never blew it again. My turbo car blew one after about 5k miles and 50 drag passes before I put the meth/H2O injection on. I put a new gasket on it and the meth/H2O inj and it has been perfect ever since (25-30k miles and ~100 more drag passes). I lean on it often.

Lou

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Home of Slant6-powered fun machines since 1988

Yeah, I'm not worried about the deck surfaces. We bought a machinist's edge and checked both sides for flatness last time and will do the same again. The plan is to pull the head before our next race just to check on the gasket since we put ~6 hours of race time on it after the swap. The last one was done after ~15 hours on track, so if we're still pinging with the new plugs I'd expect to see some fire rings starting to get toasty.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Typically on blocks it's much like exhaust manifold repairs on a much larger scale, they drill the ends of the crack to keep it from spreading, cook the block in an oven to bring the temp up uniformly, then braze the crack shut with Ni-Rod due to the high nickel content of the block, then they slowly cool in the oven or wrap in insulation.... (we have a local rural "shop"...that does the cooking on their giant outdoor BBQ pit/slag furnace....)

I think Frank is looking to do this in the car? Otherwise, he can probably find another cheap block to use...

Good luck, Frank!

Lou

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Home of Slant6-powered fun machines since 1988

Yeah, I should have mentioned that. Don't want to have to pull the motor before the next race (early November). I already plan to pull the head and manifolds, so access will be good. After the next race, we might swap this engine with the one in the parts car.

I think I'm going to try solder. I figure it'll be more ductile and less likely to crack under heat cycling than JB Weld or other epoxies, and it's a low enough melting temperature that I don't have to worry about post-heat or anything. Melting point would probably be too low for an exhaust manifold repair, but it's well above operating temperature for the block's water jacket.

How thick is the block on the driver's side? Trying to get an idea of how deep to grind the crack after I drill the ends.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Probably around 1/4" thick in that area? Could be less. I would think 1/8" deep should be enough. Look online or ask folks what is the best solder for cast iron. Probably some kind of acid core, or find a suitable flux. Silver solder might be good, but maybe too high melting for heating in that area and not cooking bearings, oilpan gasket, or something?

Lou

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Home of Slant6-powered fun machines since 1988

I would drill an 1/8" hole at each end, clean it up really good, and JB Weld it, then run a bottle of Barr's Leak in it. You're going to change blocks anyway.

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Official Cookie and Mater Tormentor.

I like Dennis' idea and that is probably what I would do.

Lou

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Home of Slant6-powered fun machines since 1988

Did it leak before you noticed the crack?

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Yeah....Im the one who destroyed this rare, vintage automobile.....

The amount of solder he's going to need is the type we use in HVAC that comes in sticks...because it has some silver in it he's going to pay $$$ for it, plus he will have to clean the crack with muriatic acid to get the base metal as clean as possible, and serve as the flux...

You might see if you HVAC buddy can sack a couple of sticks out of his van for a 6 pack for you.. and lend you his turbo torch....

Most likely I would try the JB weld trick first and if it doesn't hold... go to solder next since it will be a lot easier to clean out in that order of application/correction.