The Forestry Forum

Howdy everyone.  I just installed a 290 small cam Cummins into a gmc 9500.  (Boy that was a bigger job than I ever imagined)  it seems to me like it's sluggish.  The rpms are slow and driving it it seems like I'm loaded when I'm not.  And while driving... anytime the fuel pedal is mashed, it's smoking... a lot.  It's black gray smoke but it never clears.  On a straight stretch I can hold it down till it hits the gov and it spews smoke the whole time.  I know the turbo is spinning at idle.  I've got a boost gauge on the way.  What are your thoughts?

turbo seals. i just went thru it on a 400bc. pull your air intake off the turbo and check for oil.

Is the smoke black or blue ? restricked intake ? A 290 used more of a smoke turbo and didn't make a lot of boost .

 Could be fuel filters. That will make them smoke and be real slugish. Maybe air filter to but I would think fuel filter.

I just drove it down the road after working on it some more.  The exaust pipe blew off right after the 5in to 4 in reducer and the truck gained noticeable power and it quit smoking so bad.  So I guess my muffler is stopped up

That's good old Cummings motors sound better straight piped anyway lol

Did you replace a detroit with the 290. I don't remember the cummins haveing a 4 inch muffler, but crs could be kicking in.

Quote from: starmac on January 30, 2017, 01:13:19 AM
Did you replace a detroit with the 290. I don't remember the cummins haveing a 4 inch muffler, but crs could be kicking in.  the l10 in my ih is 4" into the muffler and 5" out

Yes the truck had a 671 Detroit in it.  It was gutless as could be but after seeing the power increase the Cummins running straight pipe.... maybe the ole Detroit wasn't as bad as I thought lol

As much smoke thar was coming thru the muffler... I never would've thought it was restricting the motor that much.   So I guess I'm gonna put straight duels on it.  It should look pretty mean. Those ole gmc 9500 look pretty mean already imo