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Help me understand, or does anyone really know...

Posted By: sycboi

Help me understand, or does anyone really know... - 03/14/18 08:19 PM

I keep reading conflicting information all over the internet about 3G Hemi rocker shaft torque specs. I’ve read a variety of numbers between 16 ft lbs to 25 ft lbs. most of the “factory torque specs” that I see copy and pasted in forums show 195 in lbs. Now here is what really confuses me. All the other M8x1.25 bolts on the engine are approximately 21 ft lbs for torque. Why are the ultra critical rocker shaft bolts only 16.25 ft lbs for the same exact bolt thread? I’ve given myself a headache just thinking about it!
Posted By: Jerry

Re: Help me understand, or does anyone really know... - 03/14/18 11:47 PM

the rocker stands are soft and can crack. probably supposed to use Loctite with the rocker shaft bolts as well. this is just a guess based on engineering knowledge and witnessing cracked rocker stands on g3 hemi heads
Posted By: GoodysGotaCuda

Re: Help me understand, or does anyone really know... - 03/15/18 01:28 AM

This is what I did, engine hasn't grenaded yet. Pay attention to whatever units you are reading...ft-lb, in-lb, Nm.

I screen-shot this just for your post directly from the manual .pdf I have on my computer. It's about as good as it gets.

Engine torque specs typically have less to do with the yield strength of the bolt and more revolved about the necessary clamping force and the material they are threading into. M8 bolts like the ones at the top of the heads are threaded into the cast iron block. The rocker bolts are threading into an aluminum head. The cast and al also have different thermal expansion rates.

That being said, follow the manual unless you have a remarkably good reason to stray from it. 195in-lbs. twocents

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Posted By: sycboi

Re: Help me understand, or does anyone really know... - 03/15/18 06:21 AM

Thank you gentlemen. That’s a bit more clear. I didn’t realize the rocker stands were that prone to issues. Maybe the rocker stand tie bars are a much better idea than I previously thought. It would help brace everything up and minimize flex...
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