KRB

FINALLY, after being down for over a year, I got the truck back together.

Milled the head, new water pump, belt, hoses and thermostat. Boiled out, cleaned & repaired radiator. Studs for the manifold. Killed the KDP which was fine, and tightened all the case bolts. New thermocoupler for the pyro. While the 190s were out I had them cleaned and popped. Painted all the parts and after just a little bleeding she fired right up. Runs fine so far but I've not pushed it yet and haven't hauled or towed either.

Now the FSM says nothing about retorquing but it seems to me the logical thing to do after a few heat/cool cycles. Generally I like to follow the FSM but I also realize its 20+ years old and things change. I also reused the original bolts as they measured within spec and one reason it took so long was buying the parts (as well as finding the time).

Thoughts?

Rick 12v CTD

what torque method did you use when doing the head bolts?

JQmile

Bolt are more forgiving than studs, but I would at least check em after a few miles.

93-12Smoke

If you torqued them per Cummins fsm then they will be difficult to check. I'm thinking that 90° rotation at the end sets it good. Bet they aren't rechecked from the factory and it lasted how many miles? I just replaced mine and the days later was pulling 20,000lbs. It held fine.

93-12Smoke

I did however let mine sit for several hours and rechecked all bolts before the 90° turn.

KRB

I did exactly per FSM.

Since it was after work between coldness, farming & family etc It was days or even weeks between each torquing sequence.

I cleaned the bolts well and used lube.

Weird part is (as mentioned in a different post) for the final 90* turn I used the torque wrench and just cranked it all the way to 150ftlbs to act as a strong arm. A few of the bolts clicked while doing the last 90*...

Good point about them not getting it from the factory or even from a shop probably. But a lot of things don't get done perfectly correctly or the "best" way becasue of cost or convenience. Just "good enough" which I'm plenty guilty of. Still, for this I don't mind to take a few minutes and check torque but I sure as heck don't want to snap a bolt off in my new head either.

Interesting about bolts being more forgiving than studs, didn't know that.

93-12Smoke

I used moly lube too. I also set my torque wrench to 150 and noticed some popped too. The purpose of the 90 is just to take the "stretch" out of the bolt. Guess some stretch way less than other.

KRB

Ah, good to know mine wasn't an anomoly.

How many miles ago was that? And I reckon you didn't retorque?

93-12Smoke

I didn't retorque mine because i didn't have a number to go off of. I put about 300 miles on the engine before the injector pump went out. But 200 of that was pulling about 20000 lbs with no issues.

93-12Smoke

The first 100 or so miles had several heat cycles tho as my drive to work is only about 3 miles

93-12Smoke

I would think if you reused your old bolts they have already been stretched from the original install. Then you torqued and stretched them more when you reinstalled them. I can't help but think they have gotta be as good as they are gonna get without risking breaking one or more. They can only be stretched so much before they break. Mine were so close to max stretch i replaced all of them.

KRB

I'll leave 'er be for now then.
Thanks,

9812vram

WATCH OUT.... ARTICLE COMING.... NOOOOOOO.....

The purpose of the last 90* is not to "take the stretch out of the bolt", but rather to put the stretch INTO the bolt. Think of long skinny elastics holding the head on - that's the point of the head bolts. Too little stretch - bad. Too much stretch - bad. The head actually moves on the head gasket with every combustion cycle which shows the importance of proper torque.

I put ARP studs in mine and torqued them all to 130ft/lbs in stages. I have the Digital TechWrenches that show Torque and Breaking Torque. I ran the truck nice and easy for 2 weeks staying under 15psi Boost, then re-torqued. Every stud's breaking torque was between 108-112 ft/lbs and breaking torque is always more than Actual Torque. This shows how much the head gasket settled after installation and heat up / cool down cycles. Each stud lost an average of 20ft/lbs of torque in those two weeks - this is over 16% loss in holding power.

Granted head studs don't have the same stretch as head bolts, but this shows how much "settling" the bolts have taken up after a fresh HG install, reducing the amount of stretch or holding power.

My buddy just re-torqued the factory head bolts on his 12 valve - 272,000 kms from factory. Breaking torque after all those miles and years was only 90ft/lbs - and like I said, breaking torque is always more than actual torque - especially 15 years after installation. He lubed and re-torqued to 130ft/lbs (over-torqued) - only two bolts couldn't handle it. Others here post the ft/lbs hitting 150ft/lbs on the 90* install method (seems way to high to me, but it get's the point across). If you knew the 90* method yielded 150ft/lbs (for argument's sake) you'd NEVER be satisfied to only torque your head bolts to 90 ft/lbs - where the original head's been sitting at since probably a year after it was built...

Is a re-torque an absolute necessity? Probably not, unless you're running high boost ie 30psi. Some of this is likely taken into account during the designing faze. They are not re-torqued from the factory, true, however lots of guys blow a HG for apparently "no reason" after a couple hundred thousand mines. A re-torque will most certainly help keep that from happening, especially if you're somewhat hotroded.

93-12Smoke

I understand your article but as far as head gaskets blowing for "no reason" is someone not knowing what they are looking for. I know after taking mine apart why it blew. Like i said above my head bolts were stretched right to the maximum limit per Cummins specs. Why after 260,000+ miles did this happen for no apparent reason? I hadn't recently pulled anything or really been hard on the truck but for four years I've been putting up to 42lbs of boost to it. The commission definitely stretches them over time and lower boosted motors should go longer unless you're hitting your max boost more often.

My problem with check torque again is you have no definite number to start with. The longest bolts got the most torque and due to them being longer i would bet the have more stretch than the shorter bolts. So where do you start when checking them? Just turn them all 1/4 turn? How do you know you're not over torqued then? You stated over torque can be as bad as under torque.

9812vram

You said basically exactly what I said... When I mentioned guys blowing HG's for "no apparent reason", I don't mean they didn't know what was leaking or where, I meant exactly what you said - no excessive boost, hard towing etc. and yet all of a sudden the HG went. It didn't blow when it was new so the question is "What changed?" Whether your HG goes due to a compression, coolant or oil leak, all these can be eradicated almost completely by maintaining a correct head torque over the life of the engine. Knowing what the failure was does not dictate the cause. Over time bolts and gasket fatigue and the head/deck warp - causing failures. Keep the sandwich tight, and it won't fatigue the same. If you had tried to "re-torque" your head bolts before the gasket blew, you likely would have found they were stretched too much. You would have installed new bolts (or studs) and torqued it up and your head gasket would still be OEM today, saving a head job etc! A re-torque could have been a good thing, even as maintenance.

As for the re-torque, the number to start with is 0. Yes, you're right, if you just tighten them up some more, you have no idea where you were and you're at, but it's not "ad-a-torque", its "re-torque". Meaning you loosen off to finger loose, then torque it back up - one bolt at a time in the correct sequence. As for the torque difference between short and long bolts - the Torque step for the shorter bolts is less than the Torque step for the longer bolts, so after they get the final 90* they should end up with the same "Stretch".

The method my buddy used with no 90* results in each bolt having the same torque - the short one's just get there quicker, but in the end, the stretch between short and long bolts is very close - just as in the factory 90* method. If you use a TechWrench when doing the 90* method it shows all bolts - regardless of length - to be generally no more than 8ft/lbs difference. That's ok though, because it's correct bolt stretch that they're really after.