In a message dated 2/6/2006 10:58:50 AM Eastern Standard Time, keltro@att.net writes:
Lynn,
Do I read this right ? You suggest going to the maximum torque in one step
instead of using two or three steps to get a more accurate torque figure ??
Could you do this with a new assembly after torqueing all fasteners to say a mid range figure then backing them off one at a time to retorque to maximum in
this single step ?? Sounds good to me !
--
Kelly Troyer
Dyke Delta/13B/RD1C/EC2
NO........................
Use the manufactures steps/torque and sequence.
When arriving at each torque value, do not stop moving the wrench until it clicks.
If you stop short of the value, and relax the torque wrench and then try to move the bolt again, the wrench will click (in most cases) seeming to indicate that the proper torque has been attained, when you know for a fact it has not.
So, for example, the first torque value may be 10 pounds. And then two more 10 pound steps to finish. Total torque is 30 pounds.
You would not even torque the first bolt to 10 pounds until all of the bolts have some amount of torque on them. Even if you do it with wrist twist to get a few pounds, just to draw things up flat. Then in sequence to 10 pounds. Then all around to 10 pounds again.
Now you will be surprised to find that many of the bolts are found to be below the 10 pound value you just torqued then too.
The rotary is worse than any cylinder head you have torqued up. It acts like a pile of goop between two steel plates. Go again at 10 pounds, and again, a few bolts will move, as though you had missed doing them. Let it sit a while and you will find a few more.
Then the 4th time around, it may feel good with no bolts moving at 10 pounds
. So, you go to 20 pounds.
And it starts all over again. So after 3 trips around the sequence at 20 pounds...................
And so on. Up to 25 or 29 pounds or whatever.
When you install the bolts do the silicone spiral, and a solid ring under the washer and around the taper in the top of the hole.
If a bolt does break (I lost one since 1980) the coolant will be retained, or most of it anyway.
The bolt head ............MAY........ not slide out and get involved with the counterweight.
If you have the sheetmetal keeper installed, it is even less likely to loose all of the coolant.
NOW.............this part is for aluminum cylinder heads on iron blocks, in piston engines.
This works just fine and saves a lot of head gaskets.
After cooldown. In the factory sequence, break the first bolt loose, and back it off one full turn.
(so some of the lube can get back in) and torque it back to the max value in one motion.
If you pay attention to the angle of the wrench before you start, and when you finish, you will notice that the bolt did screw into the block a bit further than it started out. This is all of the forces and rules involved including the bolt pedigree and the head gasket compressing a bit further.
Do the whole sequence this way, and forget about blown head gaskets. On Fiats and Cosworths anyway.
Lynn E. Hanover