1racerdude

Also from ARP site



The Torque Angle Method

Since the amount that a bolt or nut advances per degree of rotation is determined by the thread pitch, it would appear that the amount of stretch in a given bolt or stud can be accurately predicted by measuring the degrees of turn from the point where the underside of the bolt head or nut face contacts the work surface. Termed the “torque angle” method, this procedure has long been the standard of civil engineering. It has been suggested that torque angle is a relatively simple and valid procedure to use in our “blind” installations – where it is not possible to physically measure the actual bolt stretch.

ARP has conducted extensive evaluations of the torque angle method. We have concluded that, for our purposes, it is suitable only when individually calibrated for each installation.

Simple calculation of bolt stretch based on thread pitch is not accurate. No material is incompressible. When a bolt or a stud is preloaded or stretched, the components being clamped compress to some small extent. When we are looking for bolt stretch of only a few thousandths of an inch, the amount of clamped material compression becomes a very real factor.

Our investigation has proven that installed stretch is dependent, not only on the pitch of the thread and the degree of rotation, but also on the amount of compression of the clamped components, the length of the male fastener, the amount of engaged thread, the type of lubrication and the number of times that the fastener has been cycled.

For example, for the same degree of rotation, the actual amount of bolt stretch will be critically different between an aluminum cylinder head and a cast iron cylinder head – or a steel main cap on an aluminum block and a steel main cap on a cast iron block.

Further, there is a significant difference between the long and short cylinder head bolts or studs on the same head. The torque angle method can be accurate – but only if each individual installation has been previously calibrated by direct measurement of bolt stretch. When using the torque angle method, it is best to begin rotation from some small measured torque – no more than ten lb./ft. – rather than the first point of contact with the work face. To achieve accuracy it is also best to cycle the fasteners five times before either calibrating or installing.

1racerdude

Again from ARP,

Friction

Friction is an extremely challenging problem because it is so variable and difficult to control. The best way to avoid the pitfalls of friction is by using the stretch method. This way preload is controlled and independent of friction. Each time the bolt is torqued and loosened, the friction factor gets smaller. Eventually the friction levels out and becomes constant for all following repetitions. Therefore, when installing a new bolt where the stretch method cannot be used, the bolt should be tightened and loosened several times before final torque. The number of cycles depends on the lubricant. For ARP recommended lubes, five loosening and tightening cycles is sufficient.

bowtiepwr

>are they refering to actually torqing the fastener then loosening it back up 4
times before a final torque is applied between cooling cycles ?

And they are also talking about exercising the torque wrench prior to using it right?

When we use our torque wrench at work (Military) we have to actuate the torque wrench 3 time to lubricate it (torque wrench) prior to use.
Not that I am saying that our torque wrenches are totally acturate

1racerdude

They are talking about burnishing the threads(lap) for greater contact and less friction.5 times with there lube.
My TQ wrench is presumed to be good since the last time and if it had not been dropped. They get recerted every 6 month if used enough. Mack man has cal. tool at his house. I also have an electronic torque meter with audible and visual alerts I can check against.

snakeatinZ

Part number & cost????
Steve

bowtiepwr

>from Summit http://store.summitracing.com/partde...5&autoview=sku
about $60.00 and get the 12 point

bowtiepwr

>and don't forget http://store.summitracing.com/egnsea...00094&D=300094

1racerdude

The five times is on the stand before final assy. I don't retorque after a heat cycle 'cause the gaskets I use Fel Pro and Cometic don't require it.
On the final TQ on the stand I will pull down in stages and go over them a couple of times at the final TQ spec to make sure I didn't miss one and they all are tight. That's mains too. Rods are done by stretch and marked so I don't miss one. Miss one and it's blow up city out of MY pocket.

METALBEAST

Its not necessary to use BOTH the ARP thread sealer and the ARP moly lube on the head bolts. Just use the ARP thread sealer.

bowtiepwr

>the "Thread Sealer" is for the threads going through the water jacket and the "Moly Lube" is used for the "wet torque"... I just coated both sides of the washer and then did my 3 step torque sequence.

METALBEAST

I talked to two different ARP techs to confirm my thoughts, but they said the moly lube was absolutely not necessary. The thread sealer reduces the friction on the threads of the bolt and the head which is the purpose of ,moly lube. Just my $0.02 but why spend the extra money on the moly lube when the thread sealer serves a dual purpose

bowtiepwr

>so you will use the thread sealer under the head bolt "head side"?
and ARP did say that was OK for the torque proceedure?
they do a different job from one another... one seals and the other lubricates.

RE AND CHERYL

One question that was never fully answered is; Are the ARP head bolts of the Tourque To Yield type. I've looked into getting a set and they don't appear to have a seperate part number of the later model Gen I and Gen IIs that had TTY bolts from the factory. It appears the ARP bolts are just touqued to a final torque of 65ft lbs.

Am I right or wrong???

bowtiepwr

>I thought they were, but I have the head studs instead. Definately get the 12 point other wise you may not be able to fit the socket over some of the nuts/bolts.
I still can't see using thread sealer for a wet torque proceedure, the bolt heads need to tighten with little friction where if you don't use lube the torque will be off.

I lube the mating surfaces.

1racerdude

They are NOT TTY bolts.
They can be reused a bunch without buying new every time.