Cm871 vs 2250/2350

[Rockycoon75]

I'm truck shopping and have a few options. I'm really after a 09 kw with a cm871 with fresh cummins overhaul. It has 600 miles but it may already be sold. Next to options are a 2010 with a cm871 with 420k still a Virgin. The 3rd option is a 12 with a 2250/2350 (don't know enough about them to know the difference) with 550k on it. Not sure which motor is a better one. Going to be pulling hopper 80k+ in the mid west and south east. Pretty similar specs otherwise. Thanks.

[Marajin]

(01-31-2017 )Rockycoon75 Wrote:  I'm truck shopping and have a few options. I'm really after a 09 kw with a cm871 with fresh cummins overhaul. It has 600 miles but it may already be sold. Next to options are a 2010 with a cm871 with 420k still a Virgin. The 3rd option is a 12 with a 2250/2350 (don't know enough about them to know the difference) with 550k on it. Not sure which motor is a better one. Going to be pulling hopper 80k+ in the mid west and south east. Pretty similar specs otherwise. Thanks.

Just talking smak here, I am on my 2nd glass of conyak -- lol don't take it seriously ...

From factory without alterations...

- The 871 is the most sooty dirty engine they made. It eats its own poop through the EGR system at such a staggering rate that it puts 6 lbs of the stuff into the oil every 45,000 miles. Only relief that can be done without custom mods and tuning is to install a bypass filter on the oil to keep soot out and to do regular EGR tune-up work on them in hopes of keeping the DPF can at least somewhat happy.

The 871 will give check engine lights and complain about the emissions system a LOT, but it is only when it is already too late, has severe issues, and it is already causing harm to the engine.

It will not typically shut down and leave you stranded somewhere unless you have been ignoring the subtle warning signs of DPF problems and are letting it destroy itself by driving it around on a blocked up DPF can for a while.

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- The 2250 and 2350 have a bit less of the same soot-sucking issues, but are more prone to carbon packing eating the pistons and liners up, then needing an inframe at 450k miles. They also have more issues with leaky rail and have the well known problem of the fuel pump going bad with no warning. When it goes out, it destroys the entire engine in only a few hundred miles or so when it happens. Fuel pumps last a typical 400-600k miles, so it should be planned maintenance to replace its guts every 400k. Your only warning sign is a check engine light for low fuel pressure while it is happening.

BOTH of these engines will also put you on the side of the road with shutdown codes with little to no warning if the emissions system acts up much at all. Unlike the 871, that is not sensitive enough in protecting the engine, these are the opposite. They are notorious for leaving you stranded somewhere with an engine that will refuse to run, even if there is nothing much wrong with them.

The 2250/2350 engines also are more prone to liner issues. It seems to be mainly from the higher compression combined with the fact that they did not raise liner height as a prevention to compensate this. This can be corrected when an in-frame is done.

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- NONE of the red engines have any benefit over other brands like Detroit, paccar, etc. from the factory. In fact, they are generally less fuel efficient than the newer Detroits.

on the other hand -->

Moving away from factory tuning etc...

Hard to find a good custom tuner for them. 99% of all the custom tuners out there are nothing but ignorant butcher and you are no better off. Most of the time it can be worse off than leaving it alone. This especially includes all of those places that claim to do deletes that advertise on the Internet with fancy web-sites and big-names. more on this -> http://rawze.com/forums/showthread.php?tid=729

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There is a program called 'MM' (Milk Money) that is the best thing going out there for them. It corrects the bulk of their problems properly and allows for other custom mods/tuning. The program is not legal to run it in the USA or other countries that have emissions laws, just like any other delete, but many people resort to doing deletes anyways. This is because ALL of these newer emissions engines are so bad, and have so many problems, and are in the shop with high dollar repair bills so much, they will put you out of business just trying to keep them on the roads as they are from the factory. - I dont blame em.

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NON-factory ISX. Comparing them as if they all had MM in them and was done correctly (in countries where that stuff is legal) ...

The CM871 is the toughest of them. It allows for the most mods to be done and the replacement parts for them are a lot less expensive compared to the 2250/2350. Personally, I think it is the best model engine they made for these trucks so far, but only after you clean them up, put in latest ver of MM, have a decent in-frame done to them where someone raises liner height, hand-torques the head as described on this forum, etc.

The 2250/2350 are not bad, but no matter what you do the fuel pump is a time bomb waiting to kill it with no warning. Updating the fuel pump plungers and regular replacement of its guts prevents most of this, but no 100% guarantee. Injectors like to get leaky on them at 600k miles + and they are 2x the price of 871 injectors. They also like to drop a liner, because of higher compression ratios and more torque in the low end on them, so the latest ver of MM smooths the combustion process as much as can be done to help reduce this.

ALL of these engines will make other brands of engine look really bad on power, fuel efficiency and everything else with good custom tuning, so they are all pretty decent if you willing to throw the warranty in the trash can and have it done. This is even if you keep the emissions, and only have legal custom tuning done.

[Rawze]

(01-31-2017 )Rockycoon75 Wrote:  I'm truck shopping and have a few options. I'm really after a 09 kw with a cm871 with fresh cummins overhaul. It has 600 miles but it may already be sold. Next to options are a 2010 with a cm871 with 420k still a Virgin. The 3rd option is a 12 with a 2250/2350 (don't know enough about them to know the difference) with 550k on it. Not sure which motor is a better one. Going to be pulling hopper 80k+ in the mid west and south east. Pretty similar specs otherwise. Thanks.

As important as the engine, you should be looking real close at rear end ratios. pulling a constant 80k all day long really sucks with 3.36's, worse with 2.79's, etc. You need 3.79's or higher or a minimum of 3.55's.

Too high rear ratios and all your going to do is work the engine to death, complain you need more power, and wonder why you need an inframe sooner than expected.

[Rockycoon75]

They have 3.55's. One has a 10 spd the others have 18's. I have read pretty extensively on the mm on other forums. Then when I found Rawze has his own I came here. I planned on keeping the dpf tuned up per Rawze specs at least as long as there is a warranty. Already been looking at bypass filters. No problem with getting dirty or spinning wrenches. Don't know about a def system haven't found the guide to them.

BTW. How do I get to drink Conakry in the middle of the day

[Rawze]

(01-31-2017 )Rockycoon75 Wrote:  They have 3.55's. One has a 10 spd the others have 18's. I have read pretty extensively on the mm on other forums. Then when I found Rawze has his own I came here. I planned on keeping the dpf tuned up per Rawze specs at least as long as there is a warranty. Already been looking at bypass filters. No problem with getting dirty or spinning wrenches. Don't know about a def system haven't found the guide to them.

BTW. How do I get to drink Conakry in the middle of the day

make sure you look at the overhead cams before you commit. I had yet another truck here a few days ago that was all chewed up that a guy purchased.

[Rockycoon75]

Yes sir. I has a deal made on a 09. Made them pressure check coolant, dyno, and pop the valve cover. Needed intake cam and overhaul so I'm back to shopping. Trying to be cautious and read and learn as much as I can. Just don't know much about the 2250/2350 stuff.

[Rawze]

(01-31-2017 )Rockycoon75 Wrote:  Yes sir. I has a deal made on a 09. Made them pressure check coolant, dyno, and pop the valve cover. Needed intake cam and overhaul so I'm back to shopping. Trying to be cautious and read and learn as much as I can. Just don't know much about the 2250/2350 stuff.

If you liked the rest of the truck, I would have taken it for $22,000 less. Then had it hand built and done right.

[Hammerhead]

(01-31-2017 )Rockycoon75 Wrote:  Yes sir. I has a deal made on a 09. Made them pressure check coolant, dyno, and pop the valve cover. Needed intake cam and overhaul so I'm back to shopping. Trying to be cautious and read and learn as much as I can. Just don't know much about the 2250/2350 stuff.

If the '09 is going to have an inframe and has the 18 speed, that's the truck right there.
IMHO, that's the one I'd buy.
Fresh inframe, find someone to MM that baby right quick, put a bypass filter it, and smile all the way...

[Rockycoon75]

They wouldn't do it. Back online and their website for sale. Same price and no mention of the problems. Sad from a oem dealership.

Is there anything on the Cams that show they are close to the end of their life? I explained discoloration, edge chipping, dull color? I've seen ones in gas motors after they go bad but never been able to monitor a overhead one in a motor. Thanks for all of the help