New CM870 long block

[Hemiterry]

I recently had a Reman CM870 long block installed in my 2006 International 5600i tandem dump truck. The turbo is brand new as well and new EGR valve and EGR cooler. The engine is mandated with a stock tune. I’ve put around 700 miles on it and it runs good but I’m noticing grey smoke coming out of the stack even under light load. Is this normal during break in or could I have some sort of tuning or fueling issue? I’m not burning or losing any oil or coolant. Any input would be appreciated. Thanks

[Rawze]

is it a certified cummins OEM reman long block?. or one that was built at a shop and sold?.

Was the muffler changed?. .. old trucks with CM870 engines have mufflers, and they do get restrictive over the years due to soot buildup in them. A restrictive muffler can lead to improper fuel-air-mix, the turbo not spinning up as well as it should, smoke issues, and fuel mileage / power issues too.


and yeah .. sometimes the engine needs some miles and run time on it to make it stop smoking after a rebuild. As an example, my CM871 took almost 80,000 miles to fully break in after I inframed it.

[Bengy88]

What Rawze said…. Also you do know not to baby it during break in right? You want to work that engine as much as you can and not let it sit around idling and shi#t.

[Hemiterry]

Thanks for all the advice, I never thought about the muffler being a problem, I’ll look into that immediately. Today I hauled ten very heavy loads and the truck smoked less and ran stronger as the day went on. I feel like it’s just now getting into initial break-in. I’m running in southwest CO at average elevation of 6500-8000 feet so I have plenty of steep hills to really wind it up on !
Thanks everyone !