ISX and DD15 Valve Trains...

[BigRed6]

Newbie Alert!

I'm looking at trucks to purchase one. (no stealer/salespeople please) I'm a good mechanic, and I agree with the Rawze philosophy of both self-repair and intelligent, fuel-saving and safe driving. (OOG, hmmm...)

I have watched many of Rawze's repair videos, ISX rebuild, Headset, EGR Maint., etc...

I have also watched a bunch of DD15 repair videos, and like Francisco Amaya's work.
He had a DD15 that was running super rough - undriveable. The bolts had come loose on the cam mount blocks - the ALUMINUM cam mount blocks. The steel bolts had stripped-out of the Aluminum blocks. These blocks hold the cams down and the rocker tubes above them. He removed the cam blocks and sent them to a machine shop to get thread inserts put in that were replacing the factory helicoils!

This seems like the wrong place to put an aluminum block to hold down such important equipment with continuous stress, heat and wear that require such close tolerances. Seeing that video alone made me think that Mercedes had far more influence on Detroit than it appears. I can't imagine the weight savings outweighing the potential loss of reliability on that design.

I like that the ISX has steel parts up in the valve train. (please correct me if I'm wrong, but everything looked and sounded like steel and cast iron.)

That DD15 stripped threads problem alone is one reason I've decided to only look at trucks with a Cummins ISX or X15 engine. Overall, it seems to be a simpler but stronger-built engine.

I'd like to hear from other mechanics who have worked on both engines, know the repair/reliability history of both, etc...

If you drive and don't do your own mechanic work, please don't tell me how great your engine has been. Good measured driving can cover for a bad mechanical design for a long time. I'm not trying to start a "what's your favorite contest" here, just trying to get real facts on the engine designs and typical failures. I try to stay unbiased until something blatantly bad repels me from a mechanical design. It may not be a deal-breaker, but it all adds up on the pros and cons list. I want a rig that has a chance from the start to be somewhat reliable and not kill itself due to a design meant to keep the stealership shops busy or sell new trucks every couple years.

I have a hard time seeing aluminum in a big rig diesel engine, although I'm sure both have some and each have their set of weaknesses and cool stuff.

Also, rocker injection vs. common rail high-pressure injection in the ISX series. Who likes what and why? Do you think the X15 is a true improvement over the ISX?

I live in Nevada and have to drive into California many times per week, so, my truck has to be 2014 or newer for smog qualifications.

Thank you for your time and info on this!