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Mystery why did my exhaust manifolds crack

kurt

New member
"I have a Chrysler LM340 that

"I have a Chrysler LM340 that was running great on land, but when I put her in the water and ran her around a bit, I ended up with hairline cracks in the manifolds in approx same spot on both. The engine was not overheating- ran at about 170 degrees at the hottest.
Any ideas what could have caused this?
Would it be a bad idea to run it like this?
Thank you for any help you can offer!!!
Kurt"
 
"It is pulling fresh water dir

"It is pulling fresh water direct from the lake.

I think it was running more around 160, but I saw it above 160 at one point so I rounded up. I'm sure it never got above 170 for what it's worth.
What temp should it run at?

The only thing I can think of is that the previous owner did not drain the manifolds for the winter, they stress cracked and then the heat really cracked them. As I said, I ran it off a hose and there were no cracks evident. I have water and exhaust coming out the ports, so I doubt it's backpressure. Any ideas?
Thanks for any assistance you can offer!
K"
 
Are they new manifolds?
The t


Are they new manifolds?
The torque on the bolts is important.
Should be tight and leakproof but not cranked.
Manifolds can crack from expansion if the torque isnt right.
 
"What cracks manifolds is exce

"What cracks manifolds is excessive heat, variations in water flow (temporary stoppages) and freeze damage.

Jeff"
 
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