I just bought an International tractor with a 250 h.p. 855 c.i. Cummins,how could I get more power?The engine runs very good and has low hours for the age but it only pulls up to about 1900rpm,I have heard you can turn the pump up some but I don't know how.Any help is appreciated.
If that is a naturally aspirated engine I would hesitate to put much more fuel to it. Without a turbo for more air ,most likely it will just smoke more with a little power increase and high egt's. Adding fuel shims to raise high idle will also increase the fuel rail pressure so be carefull. 2100 rpm is a nice high idle for those motors.
It has a turbo,I have another 855 at 300hp that pulls good up till about 2200 and I was hoping I could get that out of this one easily.
The quick and dirty way for more fuel on a PT pump is drill out the plug in the throttle shaft and turn the slotted screw out 1/4 to 1/2 a turn. This will not increase rpm, only fuel rate. To increase rpm you must shim the gov. spring under the bell cover, if you do this you won't want to back the throttle shaft screw out. Keep in mind your motor has a smaller turbo than a 300 and is static timed differently too I think. A really dirty way to up the rpm's is a stinger bolt, a 3/8 24 fine thread bolt put in place of the 1/8 pipe plug in the bell. Just run in the bolt till it touches the idle screw and now you have no upper limit on rpm! Please don't do this, I mention it for info only, many motors have been scattered from this old stunt!
it is simple to add shims, but remember it is simple to melt an engine down if you put too many in. I would talk to a cummins guy that has spent some time in the injection lab.
I was hoping there would be a Cummins tech on here,I also was wanting to know what it would take to make my 300 a 350,it is a formula ntc 300 and International offered a formula 350 as well in the f-2275 in 81 and 82 so I was just hoping I could do it pretty cheaply.
The internals will make 350-400hp unreliable. Install a good pyrometer turn out the fuel screw in the throttle shaft 1/4-1/2 turn. Do NOT lug the engine after this. Keep your tach at 2000+ when pulling hard and the pyro under 900f. The pistons will heat seize or burn through otherwise. Run it till it comes apart then rebuild it as a 625cpl. You can inframe a 855 top to bottom, fuel system and turbo with genuine cummins parts for under 5k. If you can take apart a briggs and stratton and put it together you can do a 855.
Where can I get the info on how to do this?I was about ready io do an inframe on the 300 because it needs injector cups and I wanted to check out the rings and bearings while I was down.
If I wanted a little more out of the my 855's I generally would just change the fuel button in the pump . It's a little bit of a process but not to hard . I first check fuel pressure at the pump with a" snap test " . Use a 0 to 500 lb . pressure gauge , snap the peddle fast and see what the gauge reads . Fuel button is inside the bowl at the rear of the pump , remove bowl and snap ring and pull the valve out . The fuel button is inside the valve . It will have a number stamped on it , like say "18" or "22" . If you want more fuel to the engine go with a lower number like a "12" . Then check fuel "snap pressure again . Pressure before you change anything will probably look around 175 PSI . Experiment with different fuel buttons and stop when at 195 to 200 PSI . That 250 is similar to the old 290 . Turbo but no after cooler . They will pull hard but as mentioned don't lug it to hard for to long . I should do a thread on this with a few pictures & more detail .
Thanks td25,a thread would be nice.
Get a engine serial number for the engine you want and order parts off of that #. You will need to get a different cam gear key and reshim the cam followers to slow the timing down. You will also need to get your injectors reflowed and rework that pathetic pump. You can have a monster pump but if the injectors wont let the fuel in what good dose it do. That is what rounds camshafts and bends pushrods.
Is that the only difference internally,the cam gear key,timing and fuel system?
Throttle snap test Yeah Charles , Before you do anything with your pump first do a " snap test " . Pretty easy and gives you a reference point to start at . Remove 1/8 " pipe plug on the side of the shutoff solenoid on top of the pump and install a 0 to 300 PSI gauge . I used an old compression test unit . Start the truck up & let it warm up a bit then by hand give the throttle a quick snap to full position & let off while viewing the pressure gauge . I used my old 1973 White with 290 Cummins for example . My test topped the gauge at around 210 PSI . That truck always pulled pretty good , not quite like a 400 engine but not far from it . Years ago when we first got the truck it pulled & got the job done fine , we just wanted a little more out of the 290 so swapped the fuel button in the pump and was happy with it . Good lord ! That was 20 years ago . LOL ! The test .... http://s1016.photobucket.com/user/td25c/media/100_3196_zpsrmrqrhbk.mp4.html?sort=3&o=0
Cummins Fuel Button This is what she looks like . Not to hard to get to . Remove bowl from rear of pump housing . Then remove snap ring ( and be ready to catch it plus shims & spring )LOL ! Pull the valve out and the ( button ) is located in the end of it . It will just fall out so use caution . Mine is a number 12 button . cant remember what the truck had to begin with . Probably something like a number 24 ? Just cant remember back that far . The lower number fuel button the more fuel to the engine . I highly suggest this manual for 855 Cummins owners http://www.ebay.com/itm/Cummins-NT-...uble-Shooting-and-Repair-Manual-/331533478187 Looks like you can even buy fuel buttons on ebay . http://www.ebay.com/itm/855-Cummins...-mechanical-PT-pump-increase-HP-/261849309183
Thanks,I'll be trying that on the 250,I think I will build the 300 into something stronger if I can get the information I need.
Your 855 300 HP cummins may be closer than you think . It should have the needed after cooler in the intake manifold to keep things from melting down in a long hard pull . Your 300 does have the after cooler , Yes ?
I thought the formula had higher compression too? They had goofy timing settings.
Yessir,it has an aftercooler.
I don't know about that.I was hoping there would be a Cummins tech to drop a line on here and share some knowledge,although I know these engines are getting outdated and most of the techs these days have probably never worked on one of these engines there are still quite a few of them still out there.
Thanks for the thread all that info is really useful especially the button part.Charles
No problem Charles . A lot of good info & advice on your thread . Try the "snap test " on the 250 and the 300 when you get a chance . I'm curios to see where there at on fuel pressure now ? I still run 4 855 Cummins engines in trucks & equipment so I always like these threads . Back to your 300 build up , My buddy had a cummins book that basically was a cross reference between CPL numbers and actual part numbers of items like say the camshaft in a given engine . Say you wanted to build a 449 CPL 400 horse out of the 300 . You could look through the book and it would give part numbers and timing information on each engine . My buddy passed away and not sure what happened to all the books . I cant seem to find it on the net . You might give Cummins a call with your question .
That sounds like the book I would like to have!I will try the snap test sometime when I get started working on the trucks,right now I'm just using the 250 to move my loader and things are really hectic trying to get a couple of houses started for a builder.This year has been wetter than I can ever remember.I guess when I get started on the 300 I can ride over to Cummins South and talk to someone there,maybe they have a tech that's been into those older engines/Thanks for the help.
The big cam 300's I have seen were 350hp motors with a little less fuel. I would back out the throttle shaft screw 1/4 turn and the aneroid screw 1/4-1/2 turn and go from there. The aneroid screw is under the tin plate around the throttle shaft at about 2 o'clock. This will increase fuel off idle and make the motor more responsive.
Thanks everyone for the info,I'll be trying some of this soon.I'll keep posted.