Cracked Engine block

[RBManufacturing]

Hi Guys, Been awhile since I've been here. Hopefully someone can relate to this.
I have a 1970 c.i. ford 6 cyl. Rebuilt recently. I bought it off of e-bay, sight
unseen. I know, that was my first mistake. The water jacket in the block has
a hair line crack, about 8 inches long, about 5 inches below the exhaust manifold.
Crack is not visible, but you can see seeping anti-freeze after a few minutes running.
Only leaks when pressure builds in cooling system. I found a block sealer online called
steel seal. Sounds good. My thought is to try the steel seal, then coat the outside
of the crack with a cast iron epoxy made by Cotronics. Good for cast iron, and
up to 500 degrees F. Anyone ever used a sealer for a cracked block? Did it work?
For how long?
I would replace the motor, but is in a 1970 Ford Bronco Half Cab. Rare vehicle,
and I'm trying to keep it with all matching numbers. Any advice, or help
is GREATLY APPRECIATED!!!
Thanks, Rick @ R&B

 

[dodge man]

My opinion, its going to leak. It seems like any kind of leak stop just gunks things up, but maybe others will have opinions. Blocks can be welded, but it takes alot of work to pull the motor and all, plus you have to find someone who knows how. I'm not sure how rare and important a matching engine is for your application. I used to be into muscle cars, and it wasn't big deal to me as long as you could prove that engine was correct, even though it was a replacement. For example a car that was originally a slant six and converted to a hemi isn't correct, but a hemi car with a replaced engine seems O.K. to me. But to some collectors, matching numbers can be important.

 

[IH3444]

Usually drill a 1/8" hole at each end of crack, and weld up with Nirod. (nickel rod) by someone who truely knows how to weld well. I have had success with epoxy fixs, even along aluminum blocks, where oil passages run. I just don't recommend it.

 

[MikeD74T]

Here's another option for cast iron repairs. MikeD74T LOCK-N-STITCH Inc. homepage: Cast iron crack repair, cast iron welding, thread repair inserts

 

[20 20]

I have to say the gung will just add more head ache down the road. Do it once and do it right, find a GOOD welder.

 

[mbohuntr]

Drill the hole at each end of the crack, grind a bevel into the crack, Preheat, preheat, preheat... REAL HOT!! (I said it three times 'cause it's important) weld with nirod... Failure to pre heat will give you even worse cracking due to the increased stresses caused by localized expansion and contraction.That gunk will likely give you grief down the road. My dad had his JD '60 welded and it was still working 20 years later when he passed.

 

[ToadHill]

I've watched my dad weld several blocks and as said earlier drill small holes at each end of the crack and pre-heat. In my dad's case he heated until he had an area the length of the crack + an inch on each end and 1/2" on each side red hot then welded with nirod. He never had any returns or unhappy customers.

 

[20 20]

also with the heat up you should heat down. Once the weld is done keep heat on and slowly bring the temp down.

 

[paratrooper]

If it were my tractor I would try a slightly less expensive repair first . If you will only have a leak when pressure builds up in the cooling system then use a mix that gives a very high protection and run without a radiator cap or at least don't snap the one you have to the second position . The reason for the radiator cap is to increase pressure which raises the boiling point of the coolant . It helps to the tune of 3 degrees per pound of pressure . So at sea level with a 7 pound cap the boiling point of your coolant will be 212 plus 21 which equals 233 degree boiling point . For every 1,000 feet of altitude your 212 temp is reduced by 1 degree . Unless you are working your tractor in high temps and fierce working conditions you should have no problem . If you MUST seal the crack albeit a hairline try braising it . Cheap and quick . If you wind up with trouble still then the NiRod is probably called for .I'm just telling you what I would "try" as a first strike at the problem . Good luck .

 

[CurlyDave]

The problem with this approach is that the block is a brittle material. The crack has very sharp points which produce stress concentrations and lead to crack propagation. The entire reason for drilling the ends of the crack are to remove the stress concentrations and prevent further propagation.

Drilling is essential to stopping the crack from getting worse.

Once you have drilled, you must repair because the drilled hole is going to leak.