Correct me if I'm wrong but I haven't seen any detailed threads on re-torquing the 12 valve head bolts down to handle more boost which I'm looking into as I build up the engine a little.

Here's a good article I read online from diesel power mags you can read here on torquing the bolts down. They give 2 methods of doing it and warn the reader of torquing the bolts down more than 120 ft-lbs.

The article states the Factory Cummins torque spec is around 115 ft-lbs.
However - my Chilton manual gives the stock torque spec as
66 ft-lbs +1/4 turn for the short head bolts and 90 ft-lbs +1/4 for the long head bolts.
So....


My Question: Does anyone else have experience with this? What's the true factory specs and what specs can you push the stock bolts too?

Thanks

 

I've always replaced the head bolts cause all ur gunna wind up doing is streaching them or break them. I just pulled the head off mine cause of to much boost. I'm going back with head studs and a better head gasket. Stock bolts and gasket are designed for no more than 42psi I think

 

i would pull one and measure it to make sure it is not stretched already. then i would re torque them to 150 if there not stretched.... or just get some studs

 

How much timing and boost do you want to run?

 

@ Pyro690

40 psi

 

diesel power mag a few months back there is a truck built maximum diesel thats rund 600hp on twins and runs 11's with re-torqued stock head bolts torqued to 150 lbs. not saying i recommend this. just couldnt believe it when i was reading it.

 

...and it probably blew the headgasket the next time they started it.. haha.

 

The 98 FSM says to torque all bolts to 66, then torque only the long ones to 89, and then an additional 90* on all.

 

I would re torque to 130 if they will hold and if you can get more, go for it.

 

i use fel-pro head gasket print-o-seal
set torque at 100
run 35 lbs boost
in 5yrs i have blown 1 gasket
i dont see how you can run studs in the back of motor due to room the only way i can get pushrods in on #6 is to remove crossmember and let tranny hit the ground
still have to fight to get them in