I am in the middle of rebuilding the engine of the T/A and starting to put the parts together.
Every part has his own torque specs ,but the connectingrod nut should be torqued to 20 ft-lbs and then tighten an additional 55 degrees further with a angle gauge.
Why is that en what is the benefit of it ?

 

Its a gauge that you attach to your wrench, just like an extension. It measures the angle after pre-torque in torque-angle applications. Its used with torque to yield fasteners.

 

I'm assuming you're asking "why an angle gauge and not just a simple tq specification"...

My "basic" understanding is if you torque using an angle gauge you will more accurately stretch the bolt; i.e. you will be closer to the desired bolt stretch and clamping pressure than if had purely used torque specs.

Torque specifications are subject to variables that can be different from application to application. Example: It may take 55 ft lbs of torque to stretch a clean lubricated bolt into clean threads .1 inches. However, 55 ft lbs of torque may only stretch a dirty non-lubricated bolt into rusty threads .005 inches. Same torque specs, entirely different amounts of bolt stretch, and vastly different clamping pressures.

One way around this is to use Angle Gauges, or to actually measure the real bolt stretch where applicable. Or, you can use quality bolts like ARP that will give you torque specs based on what lubricant you use on the threads. These will get you plenty accurate results, especially if you torque cycle each bolt a few times.

 

Here is a pic.

 

what bolts/nuts are you using. stock? aftermarket?

if stock they should be new, never re-use torque to yeild bolts

if aftermarket follow the directions that came with them not the service manual

 

O.K. thanks for the reply's ,next thing on the shoppinglist.
Now i have to figure out the "Dutch" word for torque angle meter

 

If you are using the stock rod bolts don't be shy about reusing them. They are not torque to yield.

I have a stock bottom 350 that has been reassembled about 4 times and the same rods and rod bolts have been used and retorqed. The motor spins to 6800rpm shift points. Those little stock rod bolts are great!
I torque mine to 20ft:lb and eyball the angle.

Karl

 

you are contradicting yourself there, you should never reuse a bolt that is torque to yeild, ask anyone

 

I am stating that the stock rod bolts are not torque to yeild. They are not.
Let me make it clear. They are NOT. That does not mean, They ARE. They are NOT.

Karl

 

If they are not torque to yeild, what angle are you eye-balling?

 

obviously you do not know what you are talking about so maybe it would be best if you were not to give people advice.

if there is an angle after the torque than that bolt is a torque to yeild bolt and therefor it should not be reused, and eyeballing a torque angle is some of the worst advice you could give

 

tq em to 35# with oil. sounds good to me

 

surprised no one brought up the DIY cam degree wheel angle finder.

most bolts just recommend a dry and and an oiled spec assuming new hardware.

 

It is my understanding that the TA (torque-angle) method is merely a way to more accurately get a uniform clamping force from a fastener (eliminating the error for friction). Using the TA method does not necessarily mean that you are stretching a bolt to the yield point (TTY). I think one method is often mistaken for the other, when they in fact are not synonymous.

The TA method is used on TTY fasteners for accuracy in reaching the yield point. I have also read that when you tighten a bolt to the yield point, that you will actually feel it change in resistance. Using the TA method on my last rebuild, I never felt that. Once a bolt is tightened to it's yield point, it cannot be reused.

It also may be interesting to note that the GM LT1 rod bolts are the same part number for 93-97, but the manual switches from the simple 47 lb. ft. of torque to the TA method (20# + 55°) in 1995. I don't believe this makes the bolts TTY.

 

I torque mine to 45 ft lbs.