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+--- Thread: What's the difference between these pistons? (/showthread.php?tid=184)
What's the difference between these pistons? - Mrkentee - 03-14-2016
My 2010 cm871 takes a different overhaul kit than expected for typical engine of that timeframe because of my CPL. The only difference is the pistons it calls for.
Mine calls for 4376243. The other one is 4376244. Does anyone know what the difference is? I haven't been able to find out. Apparently they look the same. One chart I saw said the one mine uses was actually for cm870. Anybody know??
RE: What's the difference between these pistons? - Unilevers - 03-14-2016
i ran those numbers and literally the only thing different in those kits is the piston - the rest is the same. i believe yours is the lower horse/cpl and the other is for the larger HP engines.
RE: What's the difference between these pistons? - Mrkentee - 03-14-2016
(03-14-2016 )Unilevers Wrote: i ran those numbers and literally the only thing different in those kits is the piston - the rest is the same. i believe yours is the lower horse/cpl and the other is for the larger HP engines.Thank you. So with the 485 tune will I be ok?
RE: What's the difference between these pistons? - Mr Hagg - 03-14-2016
Unilevers I was told at one time the compression ring was lowered on the newer pistons.
RE: What's the difference between these pistons? - Mrkentee - 03-14-2016
(03-14-2016 )Mrkentee Wrote:(03-14-2016 )Unilevers Wrote: i ran those numbers and literally the only thing different in those kits is the piston - the rest is the same. i believe yours is the lower horse/cpl and the other is for the larger HP engines.Thank you. So with the 485 tune will I be ok?
To answer my own question-after reading the post about increasing horsepower, cpl, cal file; it looks like this cpl 2732 can safely be increased to 475 anyway, so I shouldn't have anything to worry about at 485. Correct me if I'm wrong. Being a former fleet truck, rhymes with lerner, I was thinking they might have intentionally built it to remain low power.
RE: What's the difference between these pistons? - Unilevers - 03-14-2016
(03-14-2016 )Mr Hagg Wrote: Unilevers I was told at one time the compression ring was lowered on the newer pistons.
you may be right on newer pistons - but in this case it is not a matter of newer, just that one piston goes with the small cpls and one goes with the large ones. both those kits are the newest numbers for their respective cpl's and both are for anti polishing ring liners.
RE: What's the difference between these pistons? - Rawze - 03-14-2016
(03-14-2016 )Mr Hagg Wrote: Unilevers I was told at one time the compression ring was lowered on the newer pistons.
Lowering the compression ring also lowers the compression ratio a bit.
Also, there were a lot of CM870 block assy's back then that were converted to CM871's from what I hear. That is likely why your CPL calls for CM870 pistons.
Lots of speculation on all this, so who knows for sure.