Cylinder Head Torque

[300sflyer]

I am in the process of trying to torque down all the cylinder head bolts, on a 98 Vortec 4.3 Chevy/Merc engine. The manual [#25] says to tighten all the bolts to 22 ft pounds, and then turn them an additional amount. [short bolts 55 degrees, medium ones 65 degrees, and the long ones 75 degrees] To me, this seems like a very inaccurate and inconsistent way of tightening them, as one must make your best guess at the angles for each bolt while doing it.

Would anyone happen to have the actual equivalent torque numbers for this?

Thank you

 

[RogersJetboat454]

Re: Cylinder Head Torque

I am in the process of trying to torque down all the cylinder head bolts, on a 98 Vortec 4.3 Chevy/Merc engine. The manual [#25] says to tighten all the bolts to 22 ft pounds, and then turn them an additional amount. [short bolts 55 degrees, medium ones 65 degrees, and the long ones 75 degrees] To me, this seems like a very inaccurate and inconsistent way of tightening them, as one must make your best guess at the angles for each bolt while doing it.

Would anyone happen to have the actual equivalent torque numbers for this?

Thank you

Sounds like you have torque-to-yield bolts, and no, there is no equivalent torque spec to degrees. The different length bolts need to be turned at different degrees in order for them to stretch correctly.

No need to guess the angles either, you can get one of these that will show you the angle;
http://www.autozone.com/autozone/accessories/Great-Neck-Torque-angle-meter?itemIdentifier=141510

BTW, you are using new head bolts, right? Torque-to-yield are one time use only.

 

[Don S]

Re: Cylinder Head Torque

Sounds like you have torque-to-yield bolts, and no, there is no equivalent torque spec to degrees. The different length bolts need to be turned at different degrees in order for them to stretch correctly.

The Chevy 4.3 does not use torque to yield bolts, they are just angle torqued because it's more accurate. New head bolts are not required or needed unless the old bolts are damaged.

 

[tpenfield]

Re: Cylinder Head Torque

Deleted

 

[Don S]

Re: Cylinder Head Torque

Best thing to do is start a new thread with your question, and not hijack 300sflyers thread with your question.

 

[300sflyer]

Re: Cylinder Head Torque

Thanks for the info guys!

I made up a cardboard protractor, and did a bit of an experiment. I torqued one head down as the manual describes, and then went back and checked the torque on each bolt. That is to say, how many foot pounds did it take to turn the bolts just a whisker more. [1 or 2 degrees] I am amazed at how close 55 degrees is to 55 FP, 65 degrees is to 65FP and 75 degrees is to 75FP!

 

[Bondo]

Re: Cylinder Head Torque

Thanks for the info guys!

I made up a cardboard protractor, and did a bit of an experiment. I torqued one head down as the manual describes, and then went back and checked the torque on each bolt. That is to say, how many foot pounds did it take to turn the bolts just a whisker more. [1 or 2 degrees] I am amazed at how close 55 degrees is to 55 FP, 65 degrees is to 65FP and 75 degrees is to 75FP!

Ayuh,.... They make a very accurate Tool fer that...

An Angle Torque gauge...