Fox T-Bird/Cougar Forums

this is something I have wondered as well.  How can you be sure that you get them all torqued properly if you are adding that extra 90* turn?  the 90* is just a guess since there is no torque wrench that I've seen that has a degree setting.

Ok just about once a month i have to use my angle torque wrench. So here is my question??? I just did those heads on the 3.4 and the GENERAL wants a 44 FT/LB initial torque followed up by 95* in sequence. So i did that and then i tested the actual torque. By twisting the bolts to 90* in stead of 95* Then used a beam torque wrench to add the final 5*. This way i could get a torque reading. So if i know the actual torque reading of the final bolt torque was 85 FT/LBS. So here is the question can i torque the head down in 3 steps to 85 Ft/Lbs and be dun with it. Comments on this any one!!

I can't imagine TTY bolts supplied by different manufacturers are exact replications of one another so therefore I can't find torque angle to be relevant anymore

This is my problem at hand. I have 2 TTY torque wrenches and they work great. BUT!!!! When i use an aftermarket head bolt arrangement or studs from ARP for example they do not recommend TTY!!!. So as i am finishing up the new engine for the Midnighter i used studs. Now studs as mentioned above never use TTY????. So as i know the engineers want the bolt on or near it's yield point how critical is it??

EXAMPLE. Some ford 3.8 V6 engines require to torque the heads down then back them off then torque them back down. Now Fel Pro says that is not necessary???????????????  So another scenario. Just something that is bothering me  is it really necessary. My research on this seems to stem from inaccurate torque wrenches or not properly prepared bolt. LUBE ETC!!  When turning a bolt a certain number of degreese torque values are not in the equation. So another thing that is rattling around in my BRAIN. Is it really necessary??????

Yeah, I'm not sure why TTY is needed. I didn't like having to do TTY on the Subaru that I replaced the head gaskets on some months ago. The entire process of working on that car, and all the things that completely fail on that vehicle at around 100k miles, make fox body repairs seem like nothing.

I'd think a properly torqued stud would still be way better than a TTY bolt. Perhaps TTY works better for aluminum parts due to the completely different rate of expansion? I could never make sense of the need for TTY other than what you found - it MAY prevent the bolt's torque from being off so much at the final torque value. Why should this even matter though? The manufacturing line and repair shops should already be using the right tools and parts, and have the education/experience to properly torque a bolt.

I just do what the manufacturer requires. I don't work on many vehicles though, so I can deal with the occasional TTY requirements.

@JeremiB 
Exactly what you said is what i understand is FACT. But check this out. Here is another wrench in the works!!! Studs for example naturally have the pitch and size of the engine they are designed for. But the nut side is normally a fine thread. This makes the clamping load more consistent. So normally they reduce the torque specks on that type of arrangement. You know something we remove and install  bolts and dont really know much about there design and function. I remove Bolts every day from brake calipers to head bolts. But do we really think about them other than what size socket we need to remove them or tighten them up???? Silly but true!! Thanks great discussion!!

Why are these 70-100ft/lb bolts so sensitive in the first place? With thick enough surfaces, it shouldn't matter at all if it's +/- 10ft/lbs. I don't think the bolts on our heavy, thick-enough fox body motors are too sensitive to the torque values compared to newer vehicles. Get it in the general vicinity and they last beyond the point where freshening up is needed. Is it due to thinner castings and aluminum being used instead of iron? That should be much more sensitive to torque values.

Pieces clamping down bearings I can see being a little more sensitive to torque. I just don't understand TTY for heads, especially when it appears to do nothing for extending the life of head gaskets or head straightness when poor choices were made elsewhere by the engineers (Subaru notably).

I don't even believe specific torque values are needed to be exact. I've always assumed that the torque was more to make sure all the bolts were the same so you do not hurt the housings or strip out threads.

Head bolt torquing involved considerable development, the difficulty being the differential expansion of the aluminum heads and steel bolts, augmented by different clamping loads resulting from two bolt lengths. Variations in bolt thread friction and bolt head to cylinder head contact friction, due to small  part-to-part manufacturing variations, resulted in significant axial bolt load variation for a specific applied bolt torque. The objective was to tighten the bolts with automatic torquing machines to provide an axial load of 10,000 to 12,000 lbs. without initiating yield, which occurs at approximately 13,500 lbs. with the 11 mm bolts used. It had been assumed that steel washers would be required to protect the aluminum head from being scored by the bolt during torquing, however, this added interface contributed to the friction variation. A "UBS" bolt, with a washer-like surface formed into the head, was evaluated and did not mar the head surface even after repeated retorquing. The automatic torquing sequence that was developed consists of:

• Install UBS head bolts and torque to 72 to 87 Nm to equalize the thread friction and set the gasket.
• Back the bolts out 2 turns.
• Retorque the bolts to 72 to 87 Nm.

The production automatic torquing machines have torque sensors and recorders. If a bolt is not torque within the specified range the operator is signaled and the suspect bolt is replaced. If a problem is encountered during hot test, or quality control durability testing, the torque applied to each head bolt on that engine can be obtained from the records. A mattress type head gasket with a solid steel core and stainless steel fire ring was developed to match the requirements of the less rigid aluminum head with its differential bolt expansion.

I remember that procedure as i was doing a tun of those head gaskets. But Fel Pro said it was not necessary with there gaskets. The perma torque gaskets did not take a set. Now back to studs. The Midnighter is fitted with studs as well as my TYPHOON. I am coming to the conclusion that studs are a waste of time. As TTY bolts are the best thing at this point. But ARP tells a different story. They claim there studs are better by a long run. So once again i am getting a HEADACHE!!!

I question how we've managed to have combustion engines for over a century. Again, I don't see the point. I only come back to the manufacturer saving money somewhere, and that's why the change. I don't think there are too many engines failing on cars, under warranty, that are due to fasteners not being TTY or too much inconsistency across bolts.

Until recently, internal combustion engines didn't care about weight savings, CAFE, use aluminum heads with iron block, etc. All these advances require more forethought for bolted joints. Reducing casting thickness and number of fasteners could very well require TTYs in order to meet reliability requirements.
The Ford case very well could be "saving money" since they added TTY somewhat late in the design process. (The head bolts weren't TTY in the 1982 paper). Maybe they needed the ~20% more clamping force a TTY gets for the same size. An upsize of the head bolt would require re-qualification at a minimum, block/head redesign at worst.

I guess we'll agree to disagree.

I was in a training course with a Dodge engineer whose job it was to minimize the length of A/C hoses to decrease weight. Etc, Etc.

I've got some aquantances I know from Honda R&D I'll see this summer. Will ask them how they are directed design-wise - performance, weight, cost.