Center section of manifold cracking..

[Rawze]

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Putting big power (above 500+ HP) in a Volvo truck is part of the issue.

Those Volvo's have beyond horrible engine compartment cooling, and severely restricted air flow. The turbo and exhaust manifold runs hotter on them than any other brand of truck because of this.

Figure out a way to cut out all the Volvo plastic crap and guards and other trash that restricts free-flowing air from getting around the engine and you will find everything runs much cooler.

(my own opinions only ... the beer is talkin') ...
Personally, I don't know why anyone would want own that brand of truck. They are the least fuel efficient of ANY truck that is aerodynamic.. they have horrible air flow and everything runs much hotter under the hood than it should.. the I-ST%it tranny is garbage (for those who have them), they have a toothpick of a drive train, and are not designed around high profitability in my book.

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What make/model engine? .... what is the boost seen under higher operating loads?. .. and What are the EGT's (and oil temps) getting up to?