The Stovebolt Site Forums The Shop Area Engine Shop need advice on welding a 235 block

I got a call today from the machinist who found a crack in the exterior water jacket between the freeze plugs on my 235. The year is a 58 if that makes a difference. What advice or tips are out there to weld this crack to save this block for the rebuild?

Thanks

Rick..........

My advice would be to find another block, there are a lot of them around.
Denny Graham
Sandwich, IL

The older 216s used to rot out and crack there. There probably is no good reason for a 235 to crack there except maybe something bad like a freeze up with water. If that is the case you don't want to use it.

Ditto! If there's an external crack, there's also the possibility of an internal one into the crankcase, etc. If you choose to attempt a repair, look into brazing instead of welding. A skilled oxy-acetyline welder can groove the crack out with a die grinder and and lay a bead of brass over it with somewhat less stress than an arc weld produces. Just get the metal VERY clean for an inch or more on both sides of the crack with a wire brush in a drill motor or the die grinder before starting the project. an arc weld with nickel-alloy rod us the strongest, nost permanent method, but the block will need to be pre-heated, peened for stress relief after the weld, and slow-cooled by burying the block in sand or some other way of preventing quick cooling of the metal. If you choose the nickel rod repair. don't weld more than an inch at a time before peening and re-heating. It's a slow, tedious process. Another block is a better choice!
Jerry

I've seen quite a few that have been cracked & welded around that area. Certainly is an option, depending on who does the work/ how good the work is done & what the extent of the damage.

Thanks for the advise. I have looked at threads and they all say about the same. It' a shame that this freshly cleaned block is a doorstop now.

Rick...........

Hello All,

a crack in a block can be devastating, but it doesn't necessarily mean its scrap. If the block is being magnafluxed it should show other cracks. Depending on the length, I don't think it should be scrap. These blocks are only going to deal with a maximum of 7lbs water pressure during operation and that really is nothing. If you are running a zero pound radiator cap it will literally be nothing. I've seen blocks that were grooved and drilled at the crack ends (to stop further propagation) and then heated to 400 degrees in a furnace, and then arc welded with a high nickel content rod. I've also seen people heli-arc them with stainless steel filling rod, brazing with brass as mentioned above, and even using cold jb weld.

Yes, to all those skeptics, cold weld does work. I still see that engine every month or so and it has been running beautifully for about 10 years since its rebuild.

Now if this were on the compression side of an engine the crack would be seeing 150-175 lbs of pressure and there I wouldn't recommend cold weld. But for seeling an external water jacket near a freeze plug opening I've seen it done.

The last option is drilling out a series of holes along the crack and filling with a series of overlaping pipe plugs. I've seen that done on heads before, but I actually think that the above methods are easier.

Just a word of caution, if you plan on heating the block up for repairs, do it before any maching is done on the block. You dont want to warp a freshly decked, bored, and aligned bored block. It will not be straight afterward, especially if it is not cooled very slowly after working. Do not quench the block at all to try and cool it, it will warp and possibly crack in other places, defeating the purpose of fixing it.

That being said, it really does depend on the length of crack and access to repair. If no other cracks show, I certainly would try and repair it.

Just my 2 cents.

54Monster

JM2¢?
I disagree.
The steps to completely identify the problem:
1. are there other cracks?
2. what other repair work is needed?
3. how expensive is it to repair, and re-machine critical surfaces?
4. most important: even if the work is "guaranteed" (if not successful, either a free new repair or a refund), does that cover towing the vehicle, removing the engine, tear-down, delivery to the shop, assembly and re-installation? What is that worth?
These must all be balanced against the cost of a replacement block (and its testing).

As to the pressure: with a zero cap, water will boil in the jacket next to the exhaust valve and spark plug far easier and earlier than with any pressure (and without the engine overheating, or a high temp gauge display). System pressure is your best insurance against temperature-induced knocking.
If the water temperature at the thermostat has not reached the kick-off level (180° etc.) the entire block's water system is under light pressure by expansion as well as local boiling, which is not readily relieved backwards to the water pump.

Any interior cavity that experiences compression also experiences combustion. The cylinder, head etc. are not limited to 150-175 compression gauge readings, but at least 700 psi.

If you're in Manila, Capetown or Auckland, finding another block is not practical, but I'd make every reasonable effort to find, price and test any used block before starting a repair.

They do some magical fixing of cracks in blocks with threaded pins that pull parts together instead of pushing apart. No heat stress. I would get another block though.

Hi, elmer 46, I work in the marine trade and there is a 2 part epoxy called Marine Tex that we have used to repair cracks in exhaust manifolds and blocks. It seems to work very well. If you use it , check the oil after every drive and look for water in the oil.If you have water in the oil you will have to find another block.