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 Post subject: NHCT270 Cummins Questions
PostPosted: Thu Dec 14, 2017 7:29 am 
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Joined: Fri Mar 25, 2005 9:59 am
Posts: 2392
Location: Daleville, PA
I have 2 questions in regards to the NHCT 270 Cummins in Russ's truck. This motor came out of a '74 Huskidrive truck.

I started working on the bracket that will mount the power steering reservoir to the engine block. I will have to rework the rod that activates the compression release. There seems to be more free play than I would expect. Does this look correct?

https://youtu.be/1tlYroBfGAM

I will also have to bend a new fuel line. I stumbled on a few links where guys T the line and provided fuel to the front of the block as well as the rear of the block. Supposedly it helped with a smoother idle and added a few HP. Any thoughts on this?

Tom

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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Thu Dec 14, 2017 11:32 am 
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Joined: Wed Nov 05, 2014 12:49 pm
Posts: 271
Location: Horseheads NY
Tom - unfortunately your link for the compression release doesn't work. I will try to explain anyway. When you pull the release lever, you should only feel resistance in the last 1/4 of the travel. This is so to provide clearance for the push rods to travel without hitting the compression release shaft. When you pull on the lever, can you feel stiff resistance in the last 1/4 of travel? If not, loosen the arm clamped on the end of the compression release shaft near the fan and rotate the arm backwards towards the passenger side of the engine while holding the shaft from moving. This will give you more actuation travel.
As for the dual inlet fuel line set up, you might see a minor improvement in full throttle performance under heavy load if you add the second inlet line. If you were to remove the return fuel line from the tank and monitor fuel flow going back to the tank you would see that there is always fuel returning back to the tank even at full throttle. This tells us the the pump is more than capable in supplying enough FLOW. The injectors require both flow and PRESSURE to work properly. Adding the second inlet will help the downstream injectors have the same FUEL PRESSURE as the injectors closest to the original fuel inlet.
Poor idle on a Cummins engine is usually related to problems with worn or weak springs in the pump itself. At idle, the fuel pressure at the head rail is only around 40 psi (depending on engine) and the fuel consumption is next to nothing. All the injectors have sufficient flow and pressure to do their job. Testing fuel pressure at idle will show that the pump is most likely at fault.
Note - be sure to inspect all fuel lines for proper diameter and to make sure there are no kinks or crushed areas that would cause a restriction.
Give me a call if you have any questions. Stan


Last edited by Huskiedrive2 on Thu Dec 14, 2017 11:44 am, edited 1 time in total.

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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Thu Dec 14, 2017 11:41 am 
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Joined: Wed Nov 05, 2014 12:49 pm
Posts: 271
Location: Horseheads NY
Tom - I got your link to work! I should have waited to respond as now I have a much better understanding as to what the problem is. The compression release linkage is shot. Notice all the lost motion in each section on the vertical shaft especially at the bottom. When you move the arm that you had your hand on, the lever at the front of the block should move almost immediately. You'll have to repair all the pieces or make new. I just finished a bare-block overhaul for a customer and tried to purchase those pieces. They are no longer available from Cummins. I have a NOS pivot casting if you need it. This would be the piece the vertical shaft passes thru. Stan


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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Thu Dec 14, 2017 7:24 pm 
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Joined: Tue May 16, 2017 8:04 pm
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I am not very familiar with compression release. Could you explain? Thanks


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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Thu Dec 14, 2017 10:00 pm 
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Joined: Wed Nov 05, 2014 12:49 pm
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Location: Horseheads NY
On the 743 series (220 Cummins) and the early 855 series (all engines) there is a shaft running in the top of the block thru the push rod gallery. When this shaft is rotated clockwise (facing the front of the engine), it comes in contact with a ring welded on each of the exhaust push rods and holds the exhaust valves open releasing compression. This allows the engine to be spun over faster during cold starting. Once the engine is spinning rapidly, the lever is released, full compression occurs in the cylinders and the engine starts. The lever shown in Tom's link is simply a bellcrank allowing the lever to be pulled from the cab instead of from under the hood.


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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Sun Dec 17, 2017 5:11 pm 
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Joined: Fri Mar 25, 2005 9:59 am
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Location: Daleville, PA
Thanks for your help Stan... that's exactly what I thought, the linkage was completely work out. I wasn't sure if there was supposed to be some free play before it engaged. I am going to try to re-bush it over the holiday.

Tom

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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Fri Dec 29, 2017 9:48 pm 
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Joined: Sun Nov 04, 2012 6:44 pm
Posts: 19
one other note, the round injecters must be installed in a certain


way for peek power. this involveds a clock postion ,1oclock working from the pump side. the last time i did 1970 on a n459tl big help


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 Post subject: Re: NHCT270 Cummins Questions
PostPosted: Sun Dec 31, 2017 10:58 am 
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Joined: Wed Nov 05, 2014 12:49 pm
Posts: 271
Location: Horseheads NY
That is true, the injectors should be installed into the head with the inlet screen in a certain position EXCEPT they should NEVER be installed with the screen pointed directly towards the fuel galley which runs parallel to the centerline of the engine. Cummins gives this explanation as to their reason, "Given the pressure and volume of fuel passing through the fuel galley, any foreign bodies in the fuel could be forced through the screen".
If the injectors are clocked slightly away from the inlet, they receive maximum flow but are protected.


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