53 Blocks - In depth question

[MAXTORQ]

Has nothing to do with it.

It's the poor cast mold that was made is the reason why they crack.

A little more reading for you.

http://www.locknstitch.com/cummins_5.9_engine_repair.htm

 

[kas83]

They don't break because of heat cycles they break because of the thinkness of the block just below the freeze plugs.

Then why don't they break the first time they are fired up? If it's all about the thinkness, it shouldn't take hardly any time to weaken and crack the block once they're fired up.

 

[kas83]

http://www.locknstitch.com/cummins_5.9_engine_repair.htm

Everything on there says it's directly linked to cold engine startup without proper warmup, thermal expansion then cracks the block at the weakest link. It is due to heat, cold, thermal stress, however you put it, it's not just due to it being too thin. It's the temperature and thermal stress that exaggerate the weakness of a thin block.

 

[MAXTORQ]

Everything on there says it's directly linked to cold engine startup without proper warmup, thermal expansion then cracks the block at the weakest link. It is due to heat, cold, thermal stress, however you put it, it's not just due to it being too thin. It's the temperature and thermal stress that exaggerate the weakness of a thin block.

So then what you are telling me that every block will crack due to thermal stress ?

This would be true if the system was abused.

Fact of matter is that if they are thinner than 8mm they will in time crack.

 

[SuperSonic]

I have seven cracked 24v 53 blocks, all with large numerals on the pump side.

 

[kas83]

So then what you are telling me that every block will crack due to thermal stress ?

This would be true if the system was abused.

Fact of matter is that if they are thinner than 8mm they will in time crack.

I'm just saying what was put in the link you provided, that it's due to thermal stress. I agree that is true if it's abused.

If they are thinner than 8mm, they will crack over time. I get that. But why do some crack earlier than others? Is there a difference between the stresses and construction of 12 valves and 24 valves that would make this problem more or less evident? And if stock power level trucks can take out the block early on, then why do some modified motors hold up? I'm not trying to dispute your claims, just wanting some more info as to what/why it happens.

I've heard of blocks cracking at around 50k miles on a couple forums, and have personal experience in my old bosses 99 when it cracked at 192k miles, as I had to take his 01 and gooseneck to pick it up. That truck was driven hard from the day he got it, always hooked to an enclosed trailer, used for deliveries 7 days a week. And Le Rae said they had a 12 valve block with 305k on it with no signs of cracking. One year and 113k miles difference, what makes it take it longer on some? Or the few that may never crack.

 

[Big Blue24]

Maybe the torque of the engine being constrained by the engine mount puts stress on the block and makes it crack. Once started, maybe it's the heat cycles that cause the crack to grow.

I suspect that if my 53 block was going to crack, it would have happened during a 3700 rpm 4x4 dropped clutch launch at the drag strip. That's got to put a lot of stress on the block!