[dataway]

I recently bought a digital torque adapter as kind of a lark to test a few of my wrenches .... and I noticed some pricey Torque Angle Gauges ... what exactly are they and and what is their use?

They measure applied torque .... and some angle, I'm not really clear on what. Are they for fasteners that specify a certain amount of rotation after seating, or something to that effect?

[AG]

They are for newer vehicles with torque to yield hardware, I had to use one on my 2000 Durango for the 4.7L head bolts. You torque to a spec and then rotate an additional amount using the angle gauge.

[1968GTO421]

Originally Posted by AG

They are for newer vehicles with torque to yield hardware, I had to use one on my 2000 Durango for the 4.7L head bolts. You torque to a spec and then rotate an additional amount using the angle gauge.

What AG said. I know guys who went with LS engines and they all require the angle gauge for building the engine. Except the few who went with ARP fasteners and then it was follow ARP's torque specs with no angle gauge involved. This is why I prefer older engines.

[Sirrotica]

FWIW, GM engines have been using TTY bolts longer than the introduction of the LS series engines. The 6.2 GM diesel was using TTY head bolts since 1984. 1982 was the year that GM started using the 1.8 Brazilian built OHC engine in the FWD J cars that also used TTY head bolts.

[dataway]

Thank you gentlemen. I have learned something new.

[lust4speed]

Which begs the question why are bolts with a one-time use better than standard bolts installed with a torque wrench? There is obviously another approach on these engines since they seem to function fine (or better?) using replacement ARP bolts? Probably a solid reason, but I just haven't heard it.

[jonmachota78]

I did head bolts on a taurus last year. The torque angle was 90 deg after torquing to a specific lbs spec. I just eyeballed 90 degrees w/o the tool. Runs great

[Schurkey]

1. Torque-Angle does not equal Torque-To-Yield. GM has reusable head bolts but still specifies torque-angle tightening. Example: '92--'93 DOHC Lumina VIN X 3.4L V6. Service manual calls for inspection of head bolts for obvious defects, but says if they look good, they can be re-used. For the record, the head bolts are the metric equivalent of 7/16; and by the time you torque-angle them into position, you've put approx. 65 ft/lbs on them. About the same as the 7/16 head bolts on a SBC.

2. Torque-Angle is a more-accurate method of getting proper clamping IF (big IF) there is proper validation of the amount of "angle" required. The concept is, most "torque" is taken up in thread friction. Small changes in thread friction make for big changes in clamping load. So you torque to some low torque value (which also means low-friction) to achieve at least some gasket crush, then add a certain amount of spin (angle) which is not dependent on friction at all. IF (big IF) the gasket crushes the correct amount, and IF the metal pieces don't excessively deform, and IF the engineering was good to begin with, you've removed a huge amount of the friction-variable from the clamp load.

3. Torque-to-Yield (TTY) goes one step further, but is often used in conjunction with Torque-Angle. The idea is that the bolt is DELIBERATELY deformed (stretched) a minimal amount in order to absolutely assure that every bit of clamp load the bolt is capable of is utilized. I think this is a wasteful, non-ecologically-sound method of crutching poor engineering. You can re-use TTY bolts, but it's not at all recommended, because every time you yield the bolt, it gets weaker. So you might get by with a second usage, but a third will be more risky, and a fourth even more risky. At some point you'll have stretched the bolt so that it's noticeably necked-down. If you're lucky, it'll break as you're tightening it. If not, it'll break later, in use. God bless ARP and "real" bolts.

[Region Warrior]

Originally Posted by lust4speed

Which begs the question why are bolts with a one-time use better than standard bolts installed with a torque wrench? There is obviously another approach on these engines since they seem to function fine (or better?) using replacement ARP bolts? Probably a solid reason, but I just haven't heard it.

Thier not.
Made of softer/smaller size to save wieght and made with less expensive materials.
They stretch and lose ability to clamp.

[mgarblik]

Schurkey has provided a "text book" explanation of the process and difference. I had to teach this stuff for decades, and his post is dead on. A little more detail for those interested. The torque to yield, and torque angle method has been around in automotive applications nearly 40 years now. Critical fasteners, like flywheel bolts, front crankshaft bolts, connecting rod bolts and sometimes main cap bolts are often taken right to the end of the elastic zone and into the yield zone where they won't go to back to their original length. (ONE TIME USE ONLY) As Shurkey mentioned, often head bolts are only taken to the elastic zone and even though an angle is specified, they can be re-used a couple times if inspected. (not a great idea IMO). The true reason they are so popular now was sort of touched on in a few other posts. Modern engines are thin/flimsy/soft materials, clamped together with smaller and fewer fasteners. A torque wrench is a dangerous tool in the hands of someone who doesn't use it properly or the wrench is junk to begin with. In the old days of iron Pontiac engines, the fasteners were so way, way over-designed and the fasteners were so big, you could have rusty, dirty threads, nicked-up bolts, a torque wrench +- 25% and the engine would be fine because the castings were so rigid. I hate to say this, but you could put an old iron engine together with impact gun and not torque anything other than the rods and it would likely stay together. It wouldn't be right, but it would run. Try that with a newer engine and it would probably not turn over and leak everywhere. Torque to yield/angle fasteners virtually eliminate rusty threads, improper lubrication of the fasteners, and lousy torque wrenches. You set a minimum preload with your torque wrench and the rest is rotational degrees. More accurate, more even clamp load.

[track73]

" I hate to say this, but you could put an old iron engine together with impact gun and not torque anything other than the rods and it would likely stay together. It wouldn't be right, but it would run."

My first job in New Mexico a student told me that's how they nailed their tractor motors together at the local IH shop. I don't know if there was any truth to that, but That's what he said.

[Sirrotica]

I've seen more than one older engine put together with an impact wrench and a breaker bar, and it ran just fine. I've also seen them so tight when first assembled that the only way to get it started was to tow it and dump the clutch to get it to turn over and when it finally started all the parts bedded in to each other. Yeah, not ideal by any means.

Also consider this, no production line engine is assembled with one man using a torque wrench and checking dimensions on each part before assembly. they are all assembled and the bolts are run in by some torque limiting/sensing powered wrench. Hundreds of thousands of these mass assembled engines live to a ripe old age trouble free.

Having worked in all types of dealerships over the years there are some that don't make the grade over the long hauls, but I would guess that 99.9% are just fine for customer commuter usage. When you're looking for maximum power and longevity is where the measurements matter and then building an engine in a week as opposed to one popping off the line every minute makes a measurable difference.

I think we can all recall where there were freaks of a certain brand that ran much better than another comparable factory built engine of the same lineage. That's where everything was spot on by chance, not by design.

Extra care in assembly of an engine has it's place for certain, but it's not in the budget for the major car makers to fit each part precisely. If it happens you get the freak that runs better than other engines of the same makeup. If it's not a stellar performer it's within factory tolerances, and closeenuff for the manufacturer to pass it on to the dealers. If it fails, that's what warranty repairs in the field are for.