NH 250 lifter housing shims

[925A1]

Has anyone changed the shim gaskets on their NH 250 / 855 to change injector timming? I have an in frame gasket set that supplies four sets of gaskets. I may be wrong, but I would think that the thinner the gasket, injectors and valve would be advanced, as the rollers would engage the cam lobes at a lower point of the lobe. I am not trying to make my engine into something different, just wondered about the results of tuning the valve train and injector time.

Thanks for any info,

Mark.

 

[WillWagner]

If you don't do it right, it will be hard starting, it'll smoke too. If you took the shims off, measure the old ones and put the cam followers back in the same position the came from.

 

[Jakelc15]

Dug this old thread up.
I was thinking of reshimming my cam followers to get a little pushrod travel. Maybe a couple thousandths of an inch more to a NHCT270 spec or 290
I'd like to keep my pt pump pressure below 200# and also keep the egts down.
I know this has to be set with the dial indicators. Then run the overhead again.
But is the small gain worth all that?
I know this would be a better gain with a turbo. (Currently installing)
The NHC250 will run many years longer with cooler temps.

Hope to get Wills professional opinion!

 

[Jakelc15]

My engine is a E code timing. My engine is a few years newer than my truck though.

 

[jarhead1086]

My engine is a E code timing. My engine is a few years newer than my truck though.

I am also interested in this tune after getting my turbo hooked up. How did you determine your timing code? The data plate by my air compressor and the one on the block are painted over.

 

[Jakelc15]

Mine is on the plate on the motor. I would think they are all the same.

 

[Jakelc15]

Our engines should all be cpl 26 cpl 544 or cpl 709.
Cpl 26 superseded by cpl 170

Nhct 270 cpl uses C timing code


Cpl 26 years 1974 and 1975 Rated engine speed changed from 2100 to 1950rpm. Field fix 20. 76SIB0-4

 

[wcuhillbilly]

opcorn:I am also curious about this too,, as I think (have to go look again) my timing code is F (1970 250 nhc recon in 83) Cummins cant find my eng # and Im fixing to take the heads, jakes, turbo, aftercooler etc off a 1977 small cam 350 and drop them on my block. Need to know how to tune this beast and currently Im on redline most of the time due to 36k lbs climbing the grades.