cummins 350 big cam safe rpm

far from the best might be the cheapest no where near a 3406b

 

the formula engines were first governed at 1900 rpm they ran between 1200 to 1900rpm. Around 1981 or so the big cam 2 then the big cam 3 then the big cam 4 mostly ran between 1200 to 1800 from the factory. The NTC engines were all 2100 rpm engines as far as I know. They were good engines.they do not have the torque that todays engines do but will still get the job done. Some of the older ones would break head bolts and the accessory drive seals would go out sometimes maybe an injector would stick from time to time but that is about all the trouble they had.you could also turn a thumbscrew on the pump and run them on manual if you had to limp in.The big cam 4 went to low flow cooling and step timing if I remember right or the 365 horse and 444 had the step timing that could torture you at times.They even had a twin turbo 475 horse engine that was mostly a disaster do not know if any are still around

 

One thing you had to be careful with especially going down hill was not to over speed the engine or you would twist the shaft off in the fuel pump. If that happened it was put a pump on along side the road or get a tow truck
afriend of mine just got a 350 in a cabover peterbilt and he is very hot headed. It did not want to run right so he held it to the floor and twisted the shaft off in the pump

 

In your opinion,the best was the kta 600 cummins followed by the big cam 3406b was good but not the best.

 

Years ago we put a stinger in a 350 Cummins pump, would easily turn 2400 rpm's and more if you let it....on the flatground, those rpm's are pushing it for the motor, 2100 is ample. In 5 weeks we put 2 turbo's on that 350, motor had no problem keeping up in the low ground, but the turbo would'nt. Gosh, that has been over 20 yrs ago.....where has time gone??


Jim

 

Valve train issues start at around 2700 with the big cams due to valve float.

 

the old 335s' had crank problems I can not remember if it was the flat nosed crank or the taper nose but one of them would tend to break and I think heat was what caused that if I remember correctly