Installing a pyrometer for 290SC Cummins

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Jan 19, 2021.

  1. mile marker 27

    mile marker 27 Light Load Member

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    ‘77 4070B, 290 small cam, with a
    #21 button. Not sure on the current HP but I’m probably going to increase the fuel pressure, with button change, cause I’m not to impressed. I’m going to install a pyrometer and was wondering about any tips or suggestions for installation around the turbo.
     
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  3. SmallPackage

    SmallPackage Road Train Member

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    Install bung and probe 5” to 6” in the pipe after the turbo. Old school Mechanical Isspro is the best.

    Ntc 290 used a #37 and light blue/red high speed spring. Just rebuilt my 250 PTG pump with a 290 fuel code.
    Only puts out 150 psi of fuel. It will turn 2500 rpm even with the weaker springs. That is fine with me cause I’m up against having a constant smoke trail with a non turbo. I may put a 30 or a 25 in it as long as it doesn’t have a hazey stack.
    The 290 will not respond until at least a #15 is installed. That is how most guys ran them down here with the 400’s.

    You need a permenant fuel pressure gauge. A small cam can flatten the lobes if pushing 225-250 psi. I have a #7 and a high output throttle shaft (1/4) hole in my 350 with an AFC pump. It pegged my fuel gauge at 200. Had to install a 300 psi gauge. Don’t hammer it hard!
     
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  4. mile marker 27

    mile marker 27 Light Load Member

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    If I were to put a #15 button in it, do I need to change the springs too? Some folks have suggested, “shims”, “throttle shaft“???? Will the overhead have to be rerun after changing the button?
     
  5. SmallPackage

    SmallPackage Road Train Member

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    Changing the big spring to a heavier one is best but You can shim it. Problem is there are 50 different springs and most cannot feel the difference in stiffness by hand. So it’s a crap shoot using salvage springs from other used pumps. Dipaco makes the high output throttle shafts in 7 different diamater “classes 1-7” but you have to know which class your pump has in it now. Standard throttle shafts are made in “classes 1-15” to compensate for machine, casting, and wear tolarances with each pump case. The H/O shafts will not work if you need anything 8-15. Like having to bore an engine cylinder to .030,.040,or .060.

    Overhead should not be nessesary if it is already good to go.
     
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  6. SmokinCAT

    SmokinCAT Road Train Member

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    You wont see any real gains until you get a set of injectors built for it that flow more than stock, the reason small cams are hard on cams is that the injector flow is pitiful so it doesn't take much to really push the pressure up.

    I install all my probes in the manifold, this is the most accurate way of reading exhaust temps.
     
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