Torque of Injector Hold-Down Bolts

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I just installed my DD Stage 3's this past Saturday, and while tightening the forward bolts for the injector hold-down straps, noticed something that left me wondering if I'd done it right.
I used a 1/4 inch drive Snap-On torque wrench and set it to 89 in. /lbs. as called for in the instructions. BUT... after tightening them to that point, I was still able to turn them, not too easily, but still able to, with a regular box end 8mm wrench...
Are these bolts liable to back out on me?
No, I didn't use an extension, or universal, which would have changed the torque. And the wrench is brand new, and definitely in calibration. I know I'm not the only one to observe this phenomenon. Educated answers from experienced mechanics would be much appreciated !

[This message has been edited by Briar Hopper (edited 08-21-2000). ]

 

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I have found 89 to be too tight and the bolts are stretching. The factory doesn't tighten them this much--more like 50 in lb. I heard they wanted to raise the spec to seal the washer better, or some such. I use a 1/4" drive ratchet and tighten them by feel to around 65-75 in lb. Pull out the ones that seemed to "need" more than 89 and see if they are stretching. If one breaks now or in service, it will ruin your day.

 

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Popped the valve cover off, took out 4 of the bolts, and measured them with my Brown & Sharpe digital calipers. All the same, all on the money. Checked the thread with a pitch gauge, no visible distortion, bending or misalignment of threads...
The "loose" feeling has to be something else... . Most experts I talked to the past few days disagreed that a 5mm (8mm hex head) grade 5 bolt would stretch that easily at 89 INCH LBS. ! I took a few bolts at work, and threaded them into a scrapped broken machine part that just happened to take 5mm bolts, and couldn't begin to stretch them even after setting the wrench on 120 inch lbs... .
Opinions differ, obviously, but thanks for your input... .

 

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Hello Briar,
We have installed 70+ sets of injectors in 24 valve engines and Use the 89 in lb. torque value, these straps have alot of leverage on the injectors and the crush washers are made of dead soft copper to get a good seal.
In one case we had to increase torque to 100 in. lb. because of a bad machine job on the seat in the head.
89 in. lb. is less than 8 ft. lb. very easy to turn with a wrench.

Ted Jannetty

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Ted Jannetty, Owner President Jannetty Racing Enterprises Inc.
97 3500 4x4 club cab 5spd. RED, JRE stage 3 power kit, JRE 4" exhaust
JRE 1/2 inch fuel system, Cummins 370 hp injectors, Prime loc,
Cummins chrome kit, US Gear 20% over drive, 3. 54 posi, Autometer
gauges, boost, and Pyrometer, BD exhaust brake.
97 Ski-Doo 670 turbocharged
99 Honda Forman 450 ES

 

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The bolts are M6 x 1. 0 thread, and the generic spec for grades 10. 9 and 12. 9 in cast iron is 9 ft-lb = 108 in-lb. So, I agree they should not be stretching at 89 in-lb. When using the torque wrench on several sets, however, the wrench kept turning while the torque would not go up noticeably, and was a little below 89 in-lb (beam type wrench). I just assumed this was due to stretch but continued crush of the copper washer or deflection of the bridge could be occurring. Either due to initial torque or "set" of the copper washer, factory bolts I have checked were not that tight.
Hope this helps,
Joe

 

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Ted, Joe,
My sincere thanks for your valuable input, I feel better now, knowing the details you just gave me, and know that I did it right...
Maybe this information will benefit others that are doing their own injector installations, I hope more than a few people read it... .
I can see it is critical not to overtighten the bolts !!!!