Torquing main and rod bolts - 93 Regal 3.8

[RVANC]

The factory manual says the main bolts require 26 ft.lb plus an additional 45 degrees. The rod bearings require 20 ft.lb plus an addition 50 degrees. I want to do what the manual says but am unsure of how accurate I can be with the additional twist. Does it matter that much? Is there a equivalent total torque that could be used instead?

Thanks.

RVC

[gmtech1]

You may check with one of the parts stores and see if they have an angle gauge that you can rent. There is no conversion that I am aware of for Lbs.Ft. You can mark a socket at 90deg intervals and use that if you need to. I would try and find a angle meter though.

[RVANC]

Thank you. It has been a long time since I've built an engine and so this is the first time I have encountered the torque plus twist approach. Have you any idea what the purpose is that a standard "torque it up to a value in increments" approach wouldn't achieve?

RVC

[gmtech1]

http://www.acl.co.nz/Tech/Torque%20T...0Headbolts.pdf

Here is some good info on "Torque to yield" bolts. The artical uses head bolts as an example, but the theory applies to them all. The bolts that use angles are "torque to yield" bolts.

[RVANC]

Thanks for the article. I have a background in engineering and what was written makes sense. If I recall correctly, back in the day they had rod bolts with spherical recesses machined in each end and the bolt was tightened until it reached a specified length determined by a micrometer measurement of the distance between two machined balls placed in the recesses. Sounds like that, a certain amount of stretch, is what is the goal with these TTY bolts is.

The article brought up a question, however. Should my rod and main bearing bolts be replaced? This will have been the second time I had the rod bearings out, this time for a new crank kit. My technique today held as closely to the torque/angle approach as I could but I probably erred on the side of overtightening them.

Thanks again.

RVC

[maxwedge]

All TTY bolts are one time use, but, to replace the rod bolts would require resizing the big end. You must have a torque angle gage as Tech11 says I would under tighten the rods and mains about 5 degrees or you will have overstretched these used bolts.

[RVANC]

I may have already overstretched the bolts considering what you guys have been saying. But I'll back them off your recommended 5 degrees (or as close as I can come to it) before I button the engine up. Perhaps that plus my well below redline driving will overcome what ever problem I may have caused.

Thanks to both of you for some great info I didn't know.

RVC