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+--- Thread: cm 870 top end rework. (/showthread.php?tid=1884)
cm 870 top end rework. - un_yun - 07-05-2017
I am currently reworking the top end on my 870. exhaust valves on 2,4,5 were dumping oil. Also inj cups on 2,3,5 where looking a little cruddy. A lot of carbon looking stuff built up in them. So a new reman head is coming(cummins said they no longer offer new)The liner height has come in good @ .22 mm or .010 in. cross hatching looks all most like a new liner. So I am going to leave them in. Cams are ok, a little varnish. But they pass inspection. I am going to roll new rods and mains in the bottom end. Is there anything in here I need to check, change, or alter while I'm in here? Oh, truck has 650,000 ish miles. thanks!!
RE: cm 870 top end rework. - hhow55 - 07-05-2017
(07-05-2017 )un_yun Wrote: I am currently reworking the top end on my 870. exhaust valves on 2,4,5 were dumping oil. Also inj cups on 2,3,5 where looking a little cruddy. A lot of carbon looking stuff built up in them. So a new reman head is coming(cummins said they no longer offer new)The liner height has come in good @ .22 mm or .010 in. cross hatching looks all most like a new liner. So I am going to leave them in. Cams are ok, a little varnish. But they pass inspection. I am going to roll new rods and mains in the bottom end. Is there anything in here I need to check, change, or alter while I'm in here? Oh, truck has 650,000 ish miles. thanks!!
Consider having you oil pump shimmed.
RE: cm 870 top end rework. - Hammerhead - 07-06-2017
Liners are a little low according to "those in the know" around here. 0.014 is the desired height.
I have had several C dealers tell me new is no longer available as well, but some searching found this to be incorrect. If you have chosen reman, be cognizant and diligent about overhead adjustments and take very careful and consistent measurements of valve heights and record them to monitor potential issues. Be prepared to change this reman head after a shorter interval than what is expected of new. Consider 400k as a possible max. I have nothing to base that on, just what I was considering when told I could only get a reman just to be safe.
When installing the head DO NOT follow C's procedure!
Instead follow this:
Torque head bolts in sequence to spec.
Wait 24hrs!
Re-torque head bolts in sequence to spec.
Now do the plus 90* rotation.
RE: cm 870 top end rework. - un_yun - 07-06-2017
(07-05-2017 )hhow55 Wrote:(07-05-2017 )un_yun Wrote: I am currently reworking the top end on my 870. exhaust valves on 2,4,5 were dumping oil. Also inj cups on 2,3,5 where looking a little cruddy. A lot of carbon looking stuff built up in them. So a new reman head is coming(cummins said they no longer offer new)The liner height has come in good @ .22 mm or .010 in. cross hatching looks all most like a new liner. So I am going to leave them in. Cams are ok, a little varnish. But they pass inspection. I am going to roll new rods and mains in the bottom end. Is there anything in here I need to check, change, or alter while I'm in here? Oh, truck has 650,000 ish miles. thanks!!
Consider having you oil pump shimmed.
8 dimes right?
RE: cm 870 top end rework. - un_yun - 07-06-2017
(07-06-2017 )Hammerhead Wrote: Liners are a little low according to "those in the know" around here. 0.014 is the desired height.
I have had several C dealers tell me new is no longer available as well, but some searching found this to be incorrect. If you have chosen reman, be cognizant and diligent about overhead adjustments and take very careful and consistent measurements of valve heights and record them to monitor potential issues. Be prepared to change this reman head after a shorter interval than what is expected of new. Consider 400k as a possible max. I have nothing to base that on, just what I was considering when told I could only get a reman just to be safe.
When installing the head DO NOT follow C's procedure!
Instead follow this:
Torque head bolts in sequence to spec.
Wait 24hrs!
Re-torque head bolts in sequence to spec.
Now do the plus 90* rotation.
I would like for them to be at .14, however .10 is well above the min, and I'm not going to be putting anymore power to it. plus I don't want to spend $2500 for the tool to cut the block right now. I figured I'd be back in it about the 400k mark. I'm not too happy about not getting a new. thnaks for the head torque!