6.2 Civi Vs. Military

[nyoffroad]

I believe the sound differance that I've encountered was from the IP timeing, if the pump timing is advance a bit you get more power but go to far and it sounds like the engine is coming apart add in the cold advance and it gets REAL loud! Try unplugging the cold advance and see if that quiets it down some if so then you know where to go.

 

[Garagefull]

I read an article years ago that stated the pre combustion chamber cups were designed in the military heads to allow them to run a broader range of fuels.I have a 1028,and 1031. Both engines are extremely loud compared to civilian. Just installed a civvy pump and injectors on a friend's 1028. It's still very loud.I have been contemplating adding a turbo, and just rounded everything up except a crossover. Maybe that will muffle it down.My pump timing is line to line. I realize that mark is just for general reference.

 

[porkysplace]

I read an article years ago that stated the pre combustion chamber cups were designed in the military heads to allow them to run a broader range of fuels.I have a 1028,and 1031. Both engines are extremely loud compared to civilian. Just installed a civvy pump and injectors on a friend's 1028. It's still very loud.I have been contemplating adding a turbo, and just rounded everything up except a crossover. Maybe that will muffle it down.My pump timing is line to line. I realize that mark is just for general reference.

Compare the casting number of the head from a military motor and civvy motor . that will tell you . I bet they are the same Gm used off the shelf parts everywhere they could on CUCV's . They also came down the same assembly line at Flint Truck and Bus as civvy trucks. The GM V.I.N. decoder and motor ID from the parts manual only list 1 J code motor . If the heads were different they would have more listed.

 

[nyoffroad]

Cool pic porky! Heads or pre cups could be different but I really doubt it.
Garagefull, try adjusting the timeing, if nothing else do it by ear and if now better then you know I'm wrong. In the past I've loosened the IP bolts useing a long 3/8 extention slid all the way from the back under the manifold.

 

[porkysplace]

Cool pic porky! Heads or pre cups could be different but I really doubt it.
Garagefull, try adjusting the timeing, if nothing else do it by ear and if now better then you know I'm wrong. In the past I've loosened the IP bolts useing a long 3/8 extention slid all the way from the back under the manifold.

GM would have different part numbers for the heads along with a different listing other than just C code and a single J code engine itself and they don't.