Cummins ntc315 specs

ive got to go put one back together and quickserve says the only manuals are available in print form due to age obviously. The serial is 11-437891. I’m looking for torque specs for main and rod bearings, head bolts, valve lash, liner height, and anything else that you gurus think I may need to know. Thanks in advance

Mike L said:

ive got to go put one back together and quickserve says the only manuals are available in print form due to age obviously. The serial is 11-437891. I’m looking for torque specs for main and rod bearings, head bolts, valve lash, liner height, and anything else that you gurus think I may need to know. Thanks in advance

Click to expand...

mike the specs would be about the same on the items you mentioned on any ntc eng if you have a manual at all. a print copy should be available on e bay cheap

Liner height .004 to .006- .003 minim, .0065 maximum.
Rods-170 lb ft
Mains-255 lb ft for 3/4" bolts
305 lb ft for 1" bolts
Heads-285 lb ft.
Intakes-.011
Exhaust-.023
Top Stop Injector-6.0 in lbs.

Mark on A Valves #5 Injector #3
B Valves #3 injector #6
C Valves #6 injector #2
A Valves #2 injector #4
B Valves #4 injector #1
C Valves #1 injector #5
Rocker Box torque-70 lb ft
Jake Heads--------- 65 lb ft
Jake lash .018-set any cylinder with closed exhaust valves.

Thank you!

Do you know what the fuel pressure should be on a bcIV 315. I am showing about 119 lbs. would like to turn it up some. what would be safe pressure to run? I will get engine serial. Is a 796 cpl. Thank you.

More data. Engine NO:11399460 NTC 315 315 @ 1800rpm Build 04-1987 S.O. 25555
an 855 093E CPL 796 ECS: AFC Injection Timing BU Injection Pump 3049186 SN: 1D1587W #27 button
Has a HT3 Turbo I believe. I would like to turn it up some with existing parts and if she runs ok, can rebuild to a different CPL. I don't know much about these engines, just things I have read on posts. Thank you for your help.

How are you checking the pressure? Snapping the throttle with a
gauge hooked to the fuel solenoid or driving down the road?
The snap test requires air pressure to open the air ratio.
Don't use a fluid filled gauge for a snap test.

Only real way to know is on a test stand.

Just the snap test. Compu Check guage and port at solenoid. I can "run it down the road" with the gauge on and tape it to the window. Only pump shop is 250 miles away. Read a lot of "threads on do this do that". Thought I could turn the screw some. Also maybe shims on the governor. Dont know how thick shim will increase speed by certain rpm. Raise it to 2500 no load and 22-2300 under load. Give more hp with the higher rpm.
I don't know if the injector nozzles will accomodate more fuel or how far to go. Read somewhere, 2hp per pound of fuel pressure but too much pressure is hard on cam, push rods, etc.
Can turn the aneroid to get fuel sooner without the boost. Not sure how much. 1/4 turn 1/2 turn ???
Will run the overhead, probably never done. Not sure I would do it right. Use the marks as described in "truck shops" post. I can and will try to learn if you folks have he patience. Thank you

You won't increase hp by raising governed speed. There are injectors from factory with more flow depending
on CPL. But rather than trying to boost hp on a 315-you may as well just build it to a common CPL like 625,
400 hp Which will involve compression change, possible injector timing change, pump/injector matched to cpl,
and possibly a turbo change because there were many HT3B turbo configurations.

I had hoped you would respond Truck Shop. I have read a number of your posts and seem quite knowledgeable. I wanted to try some quick things just to see if the engine will hold together. Then a rebuild if engine seems ok. Where do you get parts for changing cpl? I tried to talk to local cummins and didn't get much of anywhere. If you cant plug a computer into it they don't understand it.

Cummins has all but stopped support for the Small Cams, Big Cam I, II, III, Big Cam IV's and the 444.
Basically It's only N14's and up. N14 came out in 1992 so it's 30 years old. Problem is what you will
have is a warmed up 315 and probably not very impressed with it.

Most all parts will be aftermarket, and in most cases as good as Cummins. I have had good success with
Interstate McBee, Most of the gaskets will be PAI. Other small parts you will have to source on the web.
Just have the pump set up no more than 15% and AFC 10% over book. Biggest thing is condition of cylinder
block deck surface, that engine should be a NT88 block which will have lower press fit liners and counter
bores already cut for/and shims installed under liners. Blocks with LPF liners have way less counter bore
issues with leaking liners. A NT88 block also has a thicker deck area. But with all that said reality is
don't try to make more than 440 Hp. The HT 60 turbo from a N14 works well for more boost also.

Premco--in Texas is the place to send the pump and injectors-They can match flow injectors to precentage
of over fueling at the pump and account for more boost also.
Don't leave out getting 3 reman cylinder heads either. But one area that is always a concern on those old
855's is how many times has it been in-framed without changing the cam bearings/bushings. If it's idling
right now near 15 psi hot at 600 rpm, those cam bearings are the cause. Hot idle should see 19 to 21 psi.
Psi at 40 hot-if it's reading 35-cam bearings.

Pistons-use 4 ring double ni resist, doesn't really cost much more. The cam has to checked with a fine
tooth comb for any ware mainly on injector lobes. Cam followers need to be checked/each roller for
excessive up/down and side play-all rollers and roll pins can be had.

I think I have a PDF file for BC IV's I'll post it for you if I have it.

Some things to think about.

ttps://barringtondieselclub.co.za/working/ksb8874356231/cum-n855-bigcam/bc4-specification-manual.pdf

Last one I built just a few months back, I'm not building anymore. It's a 1986 BCIV CPL 676 converted to
full flow cooling of a BCIII and earlier. Approximately 435 Hp.