6.2 head bolt torque statement / question.

[tourus]

so I am now in the middle of putting the heads back on my truck m1010 6.2 diesel 1985. so put all new bolts and sealed them as per T/m's torque them as stated 20lbs then 50lbs the go a quarter turn. well being that there is not a lot of room in the engine bay. and tough to get a good 1/4 turn and be accurate . here is what I did tell me what you all might think. I did the first two steps all bolts at 50lbs. then went the full 1/4 turn on the first. then took my torque wrench and started at 80lbs found it clicked right off so went to 100lbs move the bolt slightly. back the torque wrench off to 90lbs it clicked right off. went to 95lbs slight movement the click. 1/16or so turn click.at 95lbs. torque all the rest to 95lbs. all most all went to just the 1/4 turn and a few went to just beyond but they all the same torque now. what do you guys all think.

here is a good the good side of things. if you were to go to just a 1/4 turn the last 5/6 I found to go a little more to about 1/2 or so. I would think that if it were only a 1/4 turn I would be under torque value due to the gasket being compressed to some degree at this point. so the quarter turn would be off and not the same as the first one.


this may the bad the whole head is over torqued..

but I do know that all the blots are the same torque value.

do this job with the engine in the truck the last bolts on the left head is very tough to get to so a quarter turn is very tough to judge so with a torque wrench I knew it was good.

so tell me all of your thoughts good bad and ugly. lets talk about it.

 

[cucvrus]

You should be good to go. I am not as technical as that. i do the 1/4 turn . Button it up and fire it up. No worries. Did you have the heads taken to a machine shop to be checked. I think that is more important then the exactness of the 1/4 turn. My opinion. Been there it is tough to get precise with the engine under the hood.

 

[Keith_J]

I would not reuse such head bolts. Why? They have yielded due to that 1/4 turn past 50 foot pounds. The relationship between torque and clamping force is only accurate and reproducible for low torque values. Hence the two step process with a torque wrench, the 1/4 turn now is far more accurate as it is a measure of bolt elongation, according to Hookes Law, elongation is equal to the force multiplied by length divided by bolt sectional area multiplied by modulus of elasticity...

I have not replaced a head on a 6.2 DD but I have done a few on other diesels, all with the same torque to yield bolting installation.

 

[cucvrus]

He put new bolts on it. Don't scare him.

 

[tourus]

oh yea all new bolts and sealed the heads machined .010 the new gaskets were .010 it is almost all button up waiting on new radiator should be in on mon. pick it up get it in . all new hoses water pump glow plugs. all that stuff was replaced .

 

[Keith_J]

Ok, new bolts. But still you could be off on clamping load since friction comes into play at higher torque values and friction makes bolt load all crazy. The thing the gasket needs is clamping force, the sum of all bolt loads. And they should be uniform in load.

In in really sensitive applications, bolts are heated to a specified temperature and this causes elongation, when the bolts cool, shrinkage causes load. This is normally done on high pressure flanges with metal gaskets.

 

[cucvrus]

Run it. It will go fine.

 

[Westech]

Bla Bla Bla.... You will be fine at 95 Foot pounds.
I do the same thing on all the heads I have replaced.
Some heads state a torque value and some state a low value and then 1/4 turn or 1/2 ect.
why? who the **** knows... maybe it is ezer to torque to a low value then just turn the bolt till she is tight.
People tend to jerk the wrench at high torque values. that will REALLY toss the real torque value right out then window and make it just about pointless as it can be to even state a value.
So that may be one reason.....
anyway.... your good to roll.