what are you talking about adding more air?

 

ok, using less water, to leave more air in the system, to allow for expansion.

 

I like the cap idea, what does Kurt say?

 

I did the same just tonight when putting mine back together.

I torqued teh heads up to 80lbft yesterday in 2 stages, ARP Moly, ARP studs, GM MLS.

Then left for circa 24hours, and tonight I decided to undo each nut 180degress in turn, and re-torque.

Id say most of them went an additional 45degrees over where they had been previously.

Im only doing it once though.

 

OK, I actually wrote a book on this topic (Threaded Fastner / Threaded Joint Design and Usage) with two other engineers back in 2004 while working for one of the Big Two.

Here it is in a nut-shell:

The use of studs (vs. bolts) allows a significant increase in the torque used to be applied as a clamping force vs. a force used to rotate the fastener into the material.

(Ever notice when a bolt brakes, it almost always brakes flush with the surface, this is because of the amount of force being used to twist the bolt into the material; that percentage used is about 45% of the total torque.)

With bolts, typically only 5% of the torque applied actually gets used to create the clamping force (Yeah, I know sounds VERY low, but every SAE document available confirmed this!); however, when using studs about 50% of the torque is used for clamping! That is a 1000% increase - reason enough to change from bolts to studs - if you (like MM) are pushing 96 PSI!!!

Oh, the guy who mentioned the accuracy of the typical torque wrench - Right on the Money! (Even directly after calibration, the design is simply flawed, that's why the big money guys measure bolt strech not torque when dealing with connecting rod bolts - much more accurate!)

Torque in stages??? Yep! It help equalize the torque across the material.

Heat cycles / retorque??? Sure! But it is just as effective to torque the nut to the correct amount / wait 30 minutes then retorque - the reason? "Stress relaxation" and microscopic ridges in the "flat / smooth" surfaces of the stud and nut.

Oh, the final word on how much torque is enough? In six words I can sum up EVERY paper on this topic ever published; ALL SAE docs, and even the 200+ page German Holy Grail on this topic:

"If in doubt, tighten it more!"

Oh, I don't know if these things ever became available in the US, but a company called "Nord-Lock" makes some amazing matched-pair washer products which ensure a nut / bolt will NEVER loosen. They are very cool indeed.

MIKE

OK, let the flaming from un-informed know-it-alls (who are faster than me and therefore more knowledgable in ALL automotive areas) begin!

 

it was funny that i have some nordlock washers within arms reach while reading this.. wont fit my studs tho..

and i dont think we are having stuff unscrew, just relaxing or compressing etc.

 

I torque my heads in stages, 15-30-45-60-75- and the final 85 ft-lb stages. and I let it sit overnight, recheck in the morning at 85, usually a fwe of them will torque more.

Never had head lifting problems yet.

 

So with a lack of facilities to measure bolt stretch, would using a lower initial torque, and then angular tightening be better ? as many OE seem to do now.

Or for the more DIY based people, what is the best way to go about it ?

You say, if in doubt, tighten it more !!

For our typical M11 studs on an alloy LSx motor, at what point should we fear ripping the threads from the block ?
Again, assuming our torque wrenches or torquing methods are accurate enough to use here ?

Any reccomendations as to the best torque wrench out there ( within sensible price limits )

Any thoughts on ARP Moly, different thread lubes ?

 

there is a practical limitation on this before someone tries to put 150-200 ftlbs of tq on their heads.

At some point thread shear comes into play, and the stud material yield strength comes into play as well, past that, you're just in plastic deformation and you loose all the clamping force.

 

i got an old ls1 block and old arp stud (hex hole in top is worn)...want me to see what it takes to break the stud or threads with arp moly lube?

 

You just plan on bottoming out the nut on the stud? The head thickenss, gasket, deformation of both under the nut.... all have an effect on catastrophic yield.

 

it doesnt matter to me, 90 is about all i got to give these days

getting those last kicks are like kicking to get that last pull up in gym class

 

This would be a fun experiment but you do need something to simulate the head deck thickness to make it relatable.

 

how bout......put a head on there and i have an old mls gasket!! I may do this tomorrow

 

excellent

 

I TRIPLE DOG DARE YOU !!!!!!

Seriously, it will be interesting to see the results.
If this is done on a production head, I would bet that the head will
deform WAY before the stud or threads let go.
There is not a realistic way to measure the head deforming without
running an engine hard and examining the head gasket afterwards.

Keep us posted Cablebandit!

 

I'll try to address each topic / question below:

It depends on the materials used to create the actual fastener. The harder / stronger the material, the less the fastener needs to ‘twist’ to achieve the same clamping force. Because that material specification is a known, specified quantity with OEMs, they can use angular measurements vs. torque.

Another issue to consider is percentage error; which is why the specs for angular tightening procedures are somewhat complex (e.g. - t1, t2, t3, wait 30 minutes, twist fastener X degrees, wait 30 minutes, twist another Y degrees). If a wrench is only 80% accurate, then 80% of a lower # is still (with respect to the actual amount of error, not % error) better than 80% of a higher torque value; that’s the logic anyway of T2Y fastener tightening specs.

Use a calibrated torque wrench and use the best quality fasteners you can afford!

I simply quoted all the engineer papers on the topic, but if the fasteners can accept a higher torque value, and that value is still in their elastic deformation range, then SURE!

With Aluminum, you need a depth of 4X the diameter of the fastener is avoid that issue, with Steel 2X. This is one reason I like studs – You just bottom them out! That (almost) always gives lots of extra thread depth.

In this area, price does indeed strongly correlate to quality / accuracy. Whatever you can afford, German, English, US, Swiss – all good; China / Taiwan – well, you already know… junk. Don’t buy precision tools from Harbor Freight!

Clean, lightly lubricated treads are fine, the oil will prevent the damage to the treads / block / fastener / nut. Of the research I did, no fastener manufacturers recommended anything other than a very light weight oil though.

 

Just curious, how many of you guys running 20+ psi are doing a re-tq after heat cycling them?

 

am i the only one who has broken a stud?
i was once putting the heads back on cranking down for the final pass on a bolt, cranking, cranking, cranking, the torque wrench wasnt clicking, i thought i was getting weak from all that cranking, when snap------------- broke one of the big studs.
thankfully reckless helped me out and extracted the broken stud.

 

Crap man, that'd be a nightmare. Fortunately you got it out. Were able to drill/easy out that sucker? I'd be curious too at what torque the heads deformed... I also agree before a stud breaks or threads get yanked, the stock heads would distort. The fact that they're pulling so much from such a small area I would think they would. Keep us posted!