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Crack is for losers!

Turbobus

Turbobus

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Ok mopar peeps, I present to you my first tragedy. Bought a used 78 block, had all machine work done.I assembled with 440 source 500 stroker kit, drove about 20 miles then developed a external crack on right bank pulled engine, got a 77 block and again did all the machine work and now it developed a crack on the left side after about 10 miles. Never pushed it hard like a dyno run or anything. Have a 10 psi radiator cap, according to the gauge it never got anywhere near overheating. I’ve read conflicting stories about the wall thickness of later year block castings,,,,, any suggestions or comments would be welcome.
Now broke mopar lover!
 
Sorry, but those blocks did not develop a crack after a few miles of driving, no way, no how. They should have been checked more thoroughly before using them. I just don't buy it, sorry for your luck tho.
 
Turbobus said:
Ok mopar peeps, I present to you my first tragedy. Bought a used 78 block, had all machine work done.I assembled with 440 source 500 stroker kit, drove about 20 miles then developed a external crack on right bank pulled engine, got a 77 block and again did all the machine work and now it developed a crack on the left side after about 10 miles. Never pushed it hard like a dyno run or anything. Have a 10 psi radiator cap, according to the gauge it never got anywhere near overheating. I’ve read conflicting stories about the wall thickness of later year block castings,,,,, any suggestions or comments would be welcome.
Now broke mopar lover!
Click to expand...
I think I read once about cracks forming while driving in the core plugs. Never seen it though.

1) What diameter were they bored to?
2) Were they crack checked before boring?
3) Were they sonic checked before boring?
4) Is something leaking, to let you know a crack developed?
5) Are you 100% sure, confirmed, the block itself is cracked and no chance of something up higher leaking, like a cylinder head problem? Were cylinder heads installed on second block in same position as first block, like left and right heads?
 
Later blocks being deficient was disproved a couple of times by tech articles in magazines.
 
Turbobus said:
Ok mopar peeps, I present to you my first tragedy. Bought a used 78 block, had all machine work done.I assembled with 440 source 500 stroker kit, drove about 20 miles then developed a external crack on right bank pulled engine, got a 77 block and again did all the machine work and now it developed a crack on the left side after about 10 miles. Never pushed it hard like a dyno run or anything. Have a 10 psi radiator cap, according to the gauge it never got anywhere near overheating. I’ve read conflicting stories about the wall thickness of later year block castings,,,,, any suggestions or comments would be welcome.
Now broke mopar lover!
Click to expand...
Just curious as to if you bought both blocks
from the same source? I agree with others
here. Those cracks didn't appear after your
efforts to rebuild. Any engine block (as a rule
of thumb) can handle higher temperatures.
It's freezing temps and water that kill 'em,
other than casting discrepancies.
 
External cracks are the easiest of all to repair. I'd have them both fixed. You didnt throw the first one out, did you?
(Are you usind solid motor mounts?)
 
External cracks can be repaired very easy. Look for videos on the Lock & Stitch proceedure for repairing cracks. You can do it yourself. We use this alot in my machine shop for just this type of problem. Good Luck
 
Lefty71 said:
Sorry, but those blocks did not develop a crack after a few miles of driving, no way, no how. They should have been checked more thoroughly before using them. I just don't buy it, sorry for your luck tho.
Click to expand...

I agree.... something dramatically wrong here ?
 
Repair the crack. I highly doubt it just formed. It was missed at the machine shop. The repair will depend on the crack. We have a 77 440 that's pinned. Had a crack in the freeze plug area. The machine shop we use does repairs to blocks all the time.
 
1STMP said:
Just curious as to if you bought both blocks
from the same source? I agree with others
here. Those cracks didn't appear after your
efforts to rebuild. Any engine block (as a rule
of thumb) can handle higher temperatures.
It's freezing temps and water that kill 'em,
other than casting discrepancies.
Click to expand...
Nope, got them from 2 different sources.
Blocks were vatted and i sanded down every square inch of the block and epoxy primed it, that’s not to say that I couldn’t have missed it though.
 
Do they still magna Flux things??? I think that's what it's called anyway. That will tell you if it's cracked.
 
33 IMP said:
External cracks are the easiest of all to repair. I'd have them both fixed. You didnt throw the first one out, did you?
(Are you usind solid motor mounts?)
Click to expand...
Nope, gave it to another mopar nut.
Your second comment, basically yes, they are poly bushings and basically have no give in them at all, it’s interesting you brought that up, I already decided to go back to the rubber type just in case it’s inducing some kind of undue stress, don’t know if that could be a thing or not. Have you ever repaired an external crack and how did it turn out.
 
Bobzilla said:
I think I read once about cracks forming while driving in the core plugs. Never seen it though.

1) What diameter were they bored to?
2) Were they crack checked before boring?
3) Were they sonic checked before boring?
4) Is something leaking, to let you know a crack developed?
5) Are you 100% sure, confirmed, the block itself is cracked and no chance of something up higher leaking, like a cylinder head problem? Were cylinder heads installed on second block in same position as first block, like left and right heads?
Click to expand...
4.350
Were not ndt’d
Dripping from about dead center of the left bank right about 1-1/2 below the deck, where the numbers are cast into the block,after I shut it down. Never leaked until I was doing carb work and put my foot into it. Exact same thing that happened on first block except on right bank. Both had probably less than 20 miles on them.
Put it up on friends lift and it’s definitely not coming from head gasket. I sure was hoping it was!
 
Turbobus said:
Nope, gave it to another mopar nut.
Your second comment, basically yes, they are poly bushings and basically have no give in them at all, it’s interesting you brought that up, I already decided to go back to the rubber type just in case it’s inducing some kind of undue stress, don’t know if that could be a thing or not. Have you ever repaired an external crack and how did it turn out.
Click to expand...
Stock style engine mounts with poly inserts? I wouldn't think that would cause this, but at this point who knows. Are you running rubber or poly trans mount; basically trans mount is not solid steel or aluminum, right?
Does it run smooth; any kind of unusual vibration or harmonics when it was running?
 
Are you sure it's not leaking out of one of the header bolts? That is pretty common and can look like it's leaking from the area your describing.
 
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