Maybe torque ain't so bad after all, IF ....................

[Tmoose]

My boss is a car enthusiast and recently bought a used SnapOn angle/torque wrench off ebay to work on the assortment of LS1/2/3 engines he is preparing for his Mazda RX7.

The OEM head bolt tightening spec is :
First pass 22 ft.-lbs. Second pass 90 degrees Final pass either 50 or 90 degrees, depending on bolt size.

My boss reported that when installing the heads on the most recent engine the final 90 degrees ended up within 1 ft-lb on each head.
One bank was about 2 ft-lbs higher than the other.

I guess the late, great Joe Mondello (Cr Oldsmobile) was onto something when he insisted on "torque cycling" critical fasteners a few times before that final assembly torquing.

I think The charts for ARP UltraTorque show something similar.

https://arp-bolts.com/i/t/PreloadGraph.gif

 

[kingnero]

If I read that correctly, there is no final torquing (to a specified value in Nm or ft-lbs), but the last (sometimes two) stage(s) are turn-of-the-head.
This has been around for decades, and proved itself much more accurate than torquing alone (even if several stages).

How did he measure the final torque value?

Kudos to your boss for wanting an RX7 though. I had one as a kid (low weight, turbo'd, and abused by the previous owners), sold it because I couldn't maintain/revise it like a normal suck/squeeze/bang/blow engine. I'd be interesting in owning another one now, if it weren't that my taste for cars has "improved" now...