zrxdean
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posted January 16, 2007 09:15 PM
cylinder head torque
This applies to my ZRX, but it's a general question. When disassembling a topend, have you guys ever checked to see how much torque was required to break loose the bolts/nuts? Recently I started using an 11mm ARP stud, which specified 70lbs at install. Half took 60-65 to loosen, a few less than 55. This is below the stretch point, and I wonder what's going on if anything. I used the specifed moly lube, and tightened in 10lb steps, according to OEM pattern. As suggested by ARP, I torqued and loosened all nuts 4 times before final, as a means to smooth mating surfaces. I am going to call them tomorrow, but I wonder what you guys typically find.
Dean
  
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entropy
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posted January 17, 2007 01:35 PM
 Edited By: entropy on 17 Jan 2007 15:32
Dean,
as a matter of fact...
Last weekend I bolted down the head to a new set of cases and 2 of the head bolts just felt "a little odd" as they neared the click. So I un-torqued all, and retorqued. I didn't write down the "un-tq", but i believe they all clicked before loosening.
I'm guessing it was the new cases which generated the "odd" feeling when i first torqued 'em.
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zrxdean
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posted January 17, 2007 02:24 PM
The tech at ARP suggested I heat cycle and retorque - but one nut at a time. Thus loosen just one nut, tighten to spec, loosen and tighten the next, according to OEM pattern. So as not to allow the stack to shift. Seems reasonable. PITA, but reasonable.
Thanks Karl.
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Y2KZX12R
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posted January 17, 2007 04:55 PM
Dean, I've never really checked the loostening torque. But on many engines i've noticed the same thing. Like karl said it might be the newness of the threads.
Are the threads on the ARP studs you have rolled or cut? I'd imagine there rolled in which case they shouldnt have any burs per say.
I use Moroso moly paste very sparingly (so as not to contaminate the oil) on the threads, and also on the friction surfaces of the washers and nuts.
Be carefull thou, It can effect the measured torqu reading to bolt stretch ratio quite a lot, and increases the bolt stretch for a given torque reading on a torque wrench.
I'd torque them in 3 steps. 15 ft lbs then say like 35-45 and then to 70 if thats what they recomend for proper stretch. Then loosten them one at a time like they said and retorque in one swift motion without stopping at all. Try and be consistant with the speed at which you bring each one quickly to torque.
It will be as equal in stretch as you can get.
I'll be taking my eigine apart to play with it again in a week or so. I'll check the breaking torque just to see. But i'm using oem bolts.
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zrxdean
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posted January 17, 2007 10:22 PM
They are rolled threads, very nice studs. I'll try your 2-step method next time. I'd be curious to know what your breaking torque is, even on your stock bolts. Thanks Jim.
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dougmeyer
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posted January 18, 2007 08:19 PM
In my experience, breakaway torque is almost always greater then tightening torque.
Be very careful using moly on threads. I would never do it unless the fastener manufacturer specifies it. My experience with SPS, Carillo, ARP, and others is that they recommend "oil" on the threads. When torqueing SPS bolts in Carillos we always put a little moly to prevent galling on the bottom of the bolt flange and oil on the threads. Moly on the threads can (unless you are measuring stretch) lead to overtightening due to the lower friction on the threads. We learned that when putting moly on the threads, stretch was excessive at the recommended torque. The way I do head nuts is to smear some moly on the washers but squirt the threads with oil. The best method is to lubricate as above, tighten to the recommended torque. Once you've verified the procedure then be consistent in your lubrication practice.
D.
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VincentHill
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posted January 19, 2007 10:48 AM
I always found the Nuts on the KZ1000 Motor needed to be re-Torqued after a few Heat Cycles. I figured that the Base and Head Gaskets all had to resize themselves and after that Re-Torque no problem.
When I took the 12 apart (Ape Studs) EVERYTHING Was still very tight. I Used Silver Antiseize (Small amount mixed with Oil) and used Cheap Oil to run in the engine to clear out the Silver in the Oil. Everything (Until I got inside) looked Good.
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