Rebuilding your 870 or 871? Better take a look.

[Rawze]

(06-04-2016 )Waterloo Wrote:  I forgot about that! The dealer that did my 871 in frame, sent one of my liners over to Cummins (they are right down the road) to measure and insure we got the right kit. There was a few other things Cummins did with these motors, changing things on the fly while in production. Rawze I am sure knows more about these changes than I do. I know one is the rods and mains, there are two different versions of those too.

(basing on what I have seen a lot of manufactures do...) This is what i think about it -- and is opinion only -- Basically, I think they likely they threw the engines together on the assembly line with whatever parts there were. If a block got machined a little over-sized,.. they likely simply used a thicker liner from the sig-600 series or from a QSK series motor.,.. and if only one hole was over-sized in a block,.. They likely simply used a bigger liner in that one hole only. -- Same thing for the rods etc. -- That way, they didn't have to scrap every block that had some variance? -- Just my own thoughts on it,.. but that also creates the problems downstream,,.. a million miles later when someone is trying to re-build one.

Also, I know there were a lot of blocks that were considered "conversion" blocks from what I have heard. These are left over blocks that were intended to be used as CM870 blocks,.. but ended up being used as CM871 blocks. This makes for the CPL2732 and CPL2733 arguments that I see people have about software etc. -- the liners and pistons and other parts are of a different spec. some are all steel, some have brass expansion rings, some even have different height on the compression rings, making for a different compression ratio (and requiring different software). The list is long actually, and it makes it more difficult to just throw anything you want off the shelf into an engine. -- It is also why I cringe so badly at people who say they got their parts off e-bay or from some after-market company. Most of those after-market places have no clue this is what is happening, and the parts hardly ever fit quite right.

-- Much of the time, the "standard" size sets will fit, but there are a LOT of variant engines running around out there, so no one can know for sure until that day comes when it is all apart and you are measuring everything.



In other words,... FIND SOMEONE WHO IS AN ISX SPECIALIST, and that does not necessarily mean a dealer or cummins shop. Most of them are in the dark about all this too. --- Otherwise,.. you might be sorry for all the money you spent on that inframe. Someone who is good with them will be able to explain what to look for and will already know of these variances in them already.