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Any NTC 855 experts out there?
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Mountain Mechanic
Posted 2/5/2016 11:29 (#5090077)
Subject: Any NTC 855 experts out there?


I threw a set of recon injectors in a small cam 855 with top stops in it. I have a bad feeling I punched out the tips. Barely got it started and when it ran it was terrible wit a LOT of smoke. The cylinders are loaded up with fuel bad. I used the IBC method, but don't have the little in/lbs torque wrench, so I went with zero lash. I actually think I did the damage on assembly by not backing out the adjusting screws far enough, but I'm not certain. I'v done a lot of Cummins stuff but this is only the second time I've run into top stops. I've seen some guys say they use OBC method and wondering if anyone here has experience with doing top stops this way. I kinda like the idea of knowing where the end of travel is myself. I can stand to buy the guy a set of injectors to replace the ones I wrecked, but I don't want to do it twice. Any input would be appreciated.
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a4t-1600
Posted 2/5/2016 11:52 (#5090121 - in reply to #5090077)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
Lots of things come to mind---------------are you sure they are top stop? I wouldn't of put top stops back in a small cam engine myself. Then are you absolutely sure you got the push rods in the cam follower right if removed?? Then the next thing is did you clean the cups good and seat them with a SNAP before you tongued the hold down down??




Then lets talk about the zero lash---------if there is test oil in the cups that can throw you off. I would say run it the normal way 1-6 cyl would set which ever cyl that wasn't having a valve event deal----------only set them at 45 inch lbs and then see how it runs. I would guess that you either got on the wrong stroke running the overhead or you might of mismatched some parts or not go t the inj seated in a clean bore





Should add I am not a expert-----------Been told by many on this forum that fact so hopefully some of those will chime in



Edited by a4t-1600 2/5/2016 11:56
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Mountain Mechanic
Posted 2/5/2016 12:04 (#5090148 - in reply to #5090121)
Subject: RE: Any NTC 855 experts out there?


I did clean the cups and the injectors did snap in before I torqued them. I also laid out all of the parts, including push rods, in order when disassembling. I have always been pretty stringent on putting any parts that develop a wear pattern back in the same spot, some guys have said too much so, but I don't think you can be too careful with that. I spent a quite a bit of time turning the engine by hand and watching the valve train to make sure I was on the correct cylinder, so I'm fairly confident that was good. You got me thinking on the test oil though, didn't consider that. Based on what I have told you, with the loading up and everything, would you re-run the overhead before pulling the injectors to check them?
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Dan Loehr
Posted 2/5/2016 17:44 (#5090645 - in reply to #5090148)
Subject: RE: Any NTC 855 experts out there?


Holland, Indiana (SW IN)
Darn A4t1600 in my opinion you are as close to an expert as any body I have been around if I haven't said it thank you for your help and time THANK YOU -farmers like me need a lot of help -some will bitch if you wrench it for them

Please keep up the help -I love reading your opinions -God Bless -Dan
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raider2b
Posted 2/5/2016 18:14 (#5090703 - in reply to #5090077)
Subject: RE: Any NTC 855 experts out there?


North Dakota
Are you absolutely positive they are top stops? I can't recall any small cams having the top stops. Top stops have a nut on top of the spring and only the pintle will come out. Personally I only use the outer base circle to adjust any injector because there are times when top stops are not adjusted correct from the factory. OBC method ensures the injector is closed at end of injection.

Normally when you adjust the injectors too tight it bends the push tubes.

What I think has happened is you have regular injectors and they have been adjusted too long.

One other thing to check is make sure the accessory drive is installed correctly. Roll the engine over until valves are rocking on 1 or 6, at that time the 1-6 mark should be lined up with the mark on the cover
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dakotadirt
Posted 2/5/2016 18:34 (#5090751 - in reply to #5090077)
Subject: RE: Any NTC 855 experts out there?


I've taken the 'stops' off the top stop style injectors and done the outer base circle (inch pounds torque) method. Takes out a lot of variables and is the easy way to do an overhead in my opinion. I'm no expert on this subject either but I've worked on a few over the years.
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Mountain Mechanic
Posted 2/5/2016 22:41 (#5091276 - in reply to #5090703)
Subject: RE: Any NTC 855 experts out there?


cSo I just got back from working on this thing again and when I left I only had input from a4t-1600, which was very helpful. It turns out most of you are hitting a piece of the puzzle. I went to Spencer Diesel's website to see what injectors I actually ordered since they go by CPL, and apparently what I have are called PTD injectors. They look a lot like top stops to me, I haven't done enough of these to be good at identifying them yet. I was going to try setting the injectors using the OBC method, as recommended by a4t-1600, but when I set the timing mark and studied the rocker arms things weren't looking right. I checked the injector for zero lash and it was where I set it. So then I turned the engine a little farther and checked it again and it was loose. I threw a dial indicator on #1 injector rocker arm and rotated the engine until the rocker was full down. The accessory drive is off about 60 degrees. I gave myself a new mark on the cover with a paint pen for a baseline and reran the entire overhead using the OBC method. The thing runs like a million bucks. Thanks for the input. Can somebody tell me the difference between top stop and PTD?
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a4t-1600
Posted 2/5/2016 22:41 (#5091277 - in reply to #5090148)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
YEs I would re run it------------Then a brief run . If you had the push tubes completely out of the engine be positive you dropped them back into the cam follower socket . I can't believe the ones over the years That I have encountered that were between the inj puchrod socket and a valve socket



Also I must say some pulleys are marked TDC-------------forget you ever saw that and run it by number sequence like I said earlier paying particular attention to stroke making sure no valve events are happening .


As far as the top stop thing some of the small cams got them due to cam wear but I can't remember what year------the only thing that concerns me about this project is if the wrong inj pump is with the wrong injectors-----But for comparisons sake if you ran a top stop inj in the regular manner the inj torque will come out to about 75 inch lbs. you would never see anything bent just excessive cam wear and inj wear until the inj plunger seated into the tips.



Just to be on the safe side a picture of the injectors would be a benefit to all involved-----------probably inj pump as well.




I need to thank Dan for the vote of confidence as well. Not often on this site that I get this

Edited by a4t-1600 2/6/2016 09:39
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a4t-1600
Posted 2/5/2016 22:51 (#5091296 - in reply to #5091276)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
Are the marks wore off the asecory drive pulley??? In this case it would seem some one had to stab the assecory drive in out of time-----------to verify that cyl 1-6 mark on the pulley should have the keyway at 12 o clock . you would have to pull the nut to see this but I would guess that is part of the problem.





The D injector is just a common injector that the travel is set by the adjustment screw in either the torque method or the proper method of using a dial indicator --------------the top stop sets the travel within the inj using a rubber like link that can fail. No matter which method you use it will all be within 10 inch lbs of being the same
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Mountain Mechanic
Posted 2/5/2016 23:03 (#5091319 - in reply to #5091296)
Subject: RE: Any NTC 855 experts out there?


Marks are all there. I've rebuilt several accessory drives, so that part I understand well. Apparently somebody has had the accessory drive out at some point and was unaware of the timing.
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a4t-1600
Posted 2/5/2016 23:16 (#5091341 - in reply to #5091319)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
I have also seen them shear the key on the gear and move----------either way it will need addressed at some point
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G. DAY
Posted 2/5/2016 23:59 (#5091376 - in reply to #5090077)
Subject: RE: Any NTC 855 experts out there?


Fresno, California
I ran into a small cam with the accessory drive installed improperly, and it ran like crap no power after retiming the accessory drive it ran fine.
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Mountain Mechanic
Posted 2/6/2016 13:53 (#5092399 - in reply to #5090077)
Subject: RE: Any NTC 855 experts out there?


So I have this thing running pretty good, but it has what I would call a "governor surge" especially at low idle but can carry through up to 1800 rpm. If I snap the throttle it seems to smooth out pretty good even down to low idle. It didn't do this before I opened it up. Is there something I could have done in running the overhead that could cause this? It sounds like the governor searching to me.
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a4t-1600
Posted 2/6/2016 22:10 (#5093366 - in reply to #5092399)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
your description is hard for me to decide what you are talking about---------I say no on the over head but I would contact who ever did the pump. Was the pump ran on a stand?
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Mountain Mechanic
Posted 2/6/2016 22:40 (#5093412 - in reply to #5093366)
Subject: RE: Any NTC 855 experts out there?


Didn't do anything with the pump, just injectors. Could a fresh set of injectors affect how the governor operates? The thing that's odd to me is that it didn't do it before I did the injectors, but as you can probably tell, I'm not real up on how the pt system all works. I only understand the basic concept of the pt system. I have seen with the inline and rotary pumps in the smaller engines where the pump is worn and it shows up when the injectors are replaced. The pump struggles under the higher cracking pressures. As I understand it with this system, the injectors create the high pressure, and I didn't think it was as big of a deal to do injectors without doing the pump. This thing sound like the governor isn't quite right to me, like it's overshooting and pulling it back. It's a constant surging at low idle when it's cold that smooths out at about 1800. If you warm it up and bring it back down to low idle it runs smooth.
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a4t-1600
Posted 2/9/2016 16:41 (#5099408 - in reply to #5093412)
Subject: RE: Any NTC 855 experts out there?


Dearfield Co.
Well --------my thoughts . depending on how the injectors are flowed as well as if they have the fine screen or course screen in the side of the Inj body can change things a touch . When cold they had a sort of surge at idle but not real noticeable but that is to me. I would say that the constant power governor needs adjusted but I can't remember how and can't find my book,



My description of the surge would be if the engine is cold and at a idle speed of 725 and you popped the throttle ahead to lets say 1050 rpm or 11 or 1200 rpm for faster warm up it would sound like rump rump rump and then smooth out. The 1800 rpm kind of has me scratching my head since I can't ever remember having a tractor inj pump due this. When I used to mess with a lot of the truck pumps I used the old v8--265 torque spring in them . that engine was the fore runner to the 903 and the torque spring made those engines kind of lopey but we were running big fuel on them with high flowed injectors.


My suggestion would be to call Marini diesel in Denver and ask to talk to sergio, he is the pump man and he has about 35 years in front of the machine-------they have sold out and the new owner might give some grief wanting to know to much info but sergio could help you.
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