Engine/Transmission (1998.5 - 2002) Re-torque 24 valve head bolts at valve adjust?

[Gary - K7GLD]

Has anyone checked or re-torqued the 24 valve head bolts as part of a valve adjustment? There are occasional reports of leaking head gaskets, or outright failures when trucks are modded - so wonder if a routine re-torquing might be advisable.

 

[Allnew2Me]

Gary, I asked my local diesel guru the same thing because I am getting ready to change injectors. He told me that the bolts are "stretched" at the factory and they should be left alone to insure the same settings. I think that any torque value is to do just that, stretch the fastener the proper amount for its size and purpose. My manual goes through a procedure to torque them properly but that is in the context of changing the gasket. Unless there is a leak I guess they are assumed to be properly torqued. My truck only has 60K and that may also be a factor, with a lot more maybe they are more likely to need it.

 

[obert]

Ive seen plenty of fasteners "back off", or become loose, over time. So I could see a guy feeling like that would be somthing you'd want to do.



BUT... . the head bolts are "torque to yield". Tightened with a torque wrench to take up play in the threads, the turned by degrees to a point that the bolt should be streached just about as far as it can before it breaks. The only way, really, to re-torque would be to loosen and start over. However, TTY head bolts shouldnt be trusted to use a second time, professionally, although they will last through a few if not several cycles. The last top gasket kit (for a 4BT) I got from cummins had a bolt gauge included, which measured the bolt and had a mark indicating a bolt that had been streatched too far to re- use.



I like the idea, Gary, but I dont think its practical. Periodicaly loosening the head bolts might even cause head gasket problems where they may not have ever developed in the first place.

 

[jwilliams3]

Gary,

As long as you back off and torque the bolts one by one you will be ok.

Re-torquing the bolts actually works as long as you use the Cummins specified method.

 

[Joe Mc]

Gary - I'm with the majority of the guys. Re-torquing is not mentioned in the service manual because torguing bolts isn't a "service", it's a step in part of a "repair". I also agree that if you re-torque them you could snap one or create a leak somewhere. They are already stretched out and probably locked in place as far as the threaded part. Ever have to "break" a bolt loose? If you try to re-torque you will have to overcome the force of the locked threads, which may require enough force to "pop" (snap) that bolt off in the block. I guess it's justification for a new head gasket, or fire ring and studding the head fasteners. But, if you're just looking to take care of your truck through regular maintenance then "don't do it", adjust them valves and put that cover back on. Don't loosen and retorque those head bolts - stay away. MHO

 

[blacksheepdiesel]

I re-torqued the original head bolts on the original head gasket on BlackSheep at 490,000 mi. A few of the bolts turned 1/4 to 1/2 revolution to proper torque. I had two new bolts on hand in case any of the bolts felt "soft", indicating they were stretching or about to break; still have those two extra bolts. Several friends have re-torqued both 12 & 24 valves with nary a problem; again, they all found the bolts turned when proper torque was applied to them, especially after running a few miles following a head gasket job. There is a rumor that a certain sled pulling truck on its original head gasket regularly hits 80lb boost. The head bolts are re-torqued frequently on that truck.



Godspeed,



Trent

 

[Gary - K7GLD]

HMMmmm - I appreciate the comments - looks like a fairly even split with good points on both sides - sorta simmers out to personal preference. Might check with a Cummins rep if I can corner one.



I would hope and assume that these engines are "run in" as part of the manufacturing procedure, and that after a decent heat/cool cycle, the head re-torqued - that was certainly a common and recommended procedure I did on all the engines I rebuilt over past years.



I just was curious as to how much/whether the bolts on these Cummins might loosen over time - a couple posts here suggest it DOES happen - question is, how potentially significant is that, especially on a modded engine?

 

[blacksheepdiesel]

Gary,



If the bolt is not at the proper torque then the force holding the head to the block is not at spec, right? To me that creates more of an opportunity for the gasket to fail, especially the more the engine is modded.



Godspeed,

Trent

 

[Gary - K7GLD]

Gary,



If the bolt is not at the proper torque then the force holding the head to the block is not at spec, right? To me that creates more of an opportunity for the gasket to fail, especially the more the engine is modded.



Godspeed,

Trent

That's my view as well...

 

[Jed]

At 120,000 miles we installed cam and studs when I broke loose the original studs they averaged about 25lbs less than factory torque. My mechanic said that this was due to head gasket compression over time. He has a 12 valve that runs 11s in 1/4 mile and is on stock head bolts and he checks torque every 15 to 20 passes. He says that initially they tightened up a bit but now they are solid. I do believe that there is something to the head gasket compression.

 

[obert]

Am I in the dark here? Ive only played with off-hyway 12v's that use a degree measurement for torque. I thought on hyway and 24v's used the same sequence. Is there a lb-ft spec for 24v's? The bolts turning an extra 1/4 -1/2 turn doesnt add up on the torque to degree spec.



If there is a lb-ft spec (or newton meters for those up north ) a re-torque may not be a bad idea.