Rocker arm rotates when torqued down
Thread Starter
Racer
Joined: Feb 2005
Posts: 280
Likes: 2
From: Houston TX
Rocker arm rotates when torqued down
When torquing down my rocker arms, a few of them rotate a little bit when I get them tight and close to 22 ft*lbs, so the tip of the rocker arm is no longer centered over the tip of the valve. This doesn't happen on all of them and I can't figure out how to keep them straight. It doesn't work if I hold them by hand and a wrench didn't work either. I assume that this is something that needs to be addressed - is that right or is it ok to leave those few as-is?
They are stock rockers with the Comp Cams trunion upgrade and new bolts that were included. TSP Torquer V3 cam and 7.4 pushrods, PRC .650 springs. I used a tiny bit of blue Loctite on the threads and oil on the bolt head flange, trunion face, and tip of the rocker.
They are stock rockers with the Comp Cams trunion upgrade and new bolts that were included. TSP Torquer V3 cam and 7.4 pushrods, PRC .650 springs. I used a tiny bit of blue Loctite on the threads and oil on the bolt head flange, trunion face, and tip of the rocker.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Most probably as a result of a little lifter oil bleed back--so when the rockers are torqued- it pushes the oil out of the lifter making the rockers "jiggle" a little and allowing the pushrods to spin----- I won't be worroed this is quite common---Just listen for a rapping valve when running to indicate a lifter that won't re-fill with oil to bring the lash to "0"
Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
I am thinking it is clearance between the aluminum saddle and the rocker shaft that sits in it. Have you tried moving two rockers, one that twists and one that doesn't to see if the issue follows the rocker or stays with the origina location?
If it is the saddle, LPE makes a steel version that may be more precisely machined but you would need to contact them to verify. Otherwise, new GM version may be cheaper.
If it is the saddle, LPE makes a steel version that may be more precisely machined but you would need to contact them to verify. Otherwise, new GM version may be cheaper.
Thread Starter
Racer
Joined: Feb 2005
Posts: 280
Likes: 2
From: Houston TX
Well the rockers did go together pretty easily and it looked like everything was straight, but I will double-check the ones that are rotating.
If a lifter won't re-fill with oil when the engine is running, isn't that a big problem? As you said I'd expect it to be noisy but won't that also cause excessive wear and early failure due to the slack in the valvetrain? And the valve wouldn't open fully either, right? Is this a sign of bad lifters?
I haven't tried moving two rockers but I definitely will give that a shot.
If a lifter won't re-fill with oil when the engine is running, isn't that a big problem? As you said I'd expect it to be noisy but won't that also cause excessive wear and early failure due to the slack in the valvetrain? And the valve wouldn't open fully either, right? Is this a sign of bad lifters?
I haven't tried moving two rockers but I definitely will give that a shot.
Last edited by NewFoundPower; Nov 19, 2012 at 12:42 PM.
Le Mans Master
Joined: Sep 2003
Posts: 6,276
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From: Farmington CT
Cruise-In VII Veteran
are you tq'ing them down when the lifter is on the base of the cam? or are they compressing the spring as you tighten them down?
this is a common issue if your on the lobe of the cam when tightening
this is a common issue if your on the lobe of the cam when tightening
Thread Starter
Racer
Joined: Feb 2005
Posts: 280
Likes: 2
From: Houston TX
Yes, but I had to use the TDC method because I put the timing cover on before I did the rockers (obviously wasn't planning ahead). I stick a thin rod in through the spark plug hole and can feel the top of the piston, then I tighten and torque the rockers.
Team Owner
Joined: Mar 2002
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Most probably as a result of a little lifter oil bleed back--so when the rockers are torqued- it pushes the oil out of the lifter making the rockers "jiggle" a little and allowing the pushrods to spin----- I won't be worroed this is quite common---Just listen for a rapping valve when running to indicate a lifter that won't re-fill with oil to bring the lash to "0"
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
This may or may not put you on the TDC of the firing cycle. The intake should have just closed when the piston comes up vice the exhaust closing.
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Thread Starter
Racer
Joined: Feb 2005
Posts: 280
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From: Houston TX
So I want the piston to be at the top of the bore after the intake valve has closed but before the exhaust valve opens, right? And to confirm this, I should be able to keep rotating the engine without either valve opening, which would be the combustion stroke. That should give me a window of rotation with base circle contact on at least two cylinders, right?
Team Owner
Joined: Mar 2002
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So I want the piston to be at the top of the bore after the intake valve has closed but before the exhaust valve opens, right? And to confirm this, I should be able to keep rotating the engine without either valve opening, which would be the combustion stroke. That should give me a window of rotation with base circle contact on at least two cylinders, right?
1. Intake (Down)
2. Compression (Up)
3. Power (Down)
4. Exhaust (Up)
Hence the common mnemonic "suck, squeeze, bang, blow"
You can be Top Dead Center at the transition from 2-3 or 4-1. To ensure you're off cam lobes, you want the prior (2-3) or in other words the end of the compression stroke. You can verify that's where you are by watching both your stick in the plug hole and the pushrods. Stick comes out (up), pushrods don't move ... that's compression stroke.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Originally Posted by tblu92
Most probably as a result of a little lifter oil bleed back--so when the rockers are torqued- it pushes the oil out of the lifter making the rockers "jiggle" a little and allowing the pushrods to spin----- I won't be worroed this is quite common---Just listen for a rapping valve when running to indicate a lifter that won't re-fill with oil to bring the lash to "0"
No
NO What ????????
Most probably as a result of a little lifter oil bleed back--so when the rockers are torqued- it pushes the oil out of the lifter making the rockers "jiggle" a little and allowing the pushrods to spin----- I won't be worroed this is quite common---Just listen for a rapping valve when running to indicate a lifter that won't re-fill with oil to bring the lash to "0"
No
NO What ????????
Team Owner
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No, the loss of oil in a lifter will not cause the rocker arm to rotate out of place when the nut is tightened. Lifters will start to bleed down the second oil pressure is gone. When you torque that nut to 22 ft-lbs, you're preloading against the spring in the lifter and not hydraulic pressure. His issue is most likely as Steve noted, in that he's trying to tighten a rocker while the lifter is riding on a cam lobe. When you try to do that, the rocker won't seat properly on that big aluminum bar/saddle because of the pressure exerted on it by the pushrod. Hence it twists out of place when the rocker nut is torqued.
So no, pretty much everything you said was incorrect and inapplicable.
So no, pretty much everything you said was incorrect and inapplicable.
Team Owner
Joined: Mar 1999
Posts: 22,025
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From: At the beach in little Rhody
No, the loss of oil in a lifter will not cause the rocker arm to rotate out of place when the nut is tightened. Lifters will start to bleed down the second oil pressure is gone. When you torque that nut to 22 ft-lbs, you're preloading against the spring in the lifter and not hydraulic pressure. His issue is most likely as Steve noted, in that he's trying to tighten a rocker while the lifter is riding on a cam lobe. When you try to do that, the rocker won't seat properly on that big aluminum bar/saddle because of the pressure exerted on it by the pushrod. Hence it twists out of place when the rocker nut is torqued.
So no, pretty much everything you said was incorrect and inapplicable.
So no, pretty much everything you said was incorrect and inapplicable.
Le Mans Master
Joined: Sep 2003
Posts: 6,276
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From: Farmington CT
Cruise-In VII Veteran
if your tightening down on a cam lobe for the given valve..............the rocker is going to walk to the left or right...............it's that simple.
lifter bleed down??? again........tighten down on the 'base' of the cam lobe or 'no lift'
you may also notice that an 11mm wrench holds the rocker from moving
lifter bleed down??? again........tighten down on the 'base' of the cam lobe or 'no lift'
you may also notice that an 11mm wrench holds the rocker from moving
Team Owner
Joined: Mar 2002
Posts: 24,160
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If the rocker doesn't "seat" and the torque value is reached, then the rocker will loosen as soon as the motor starts since you are effectively stating there is no preload in the bolted joint. Since the OP hasn't stated that he has issues with the rockers loosening the rocker must be fully seated within the aluminum saddle.
Last edited by wcsinx; Nov 21, 2012 at 11:06 AM.
Team Owner
Joined: Mar 2002
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If you're tightening against the valve spring, how do you know when you've got the right torque on the nut?
Thread Starter
Racer
Joined: Feb 2005
Posts: 280
Likes: 2
From: Houston TX
I haven't tried to start the car yet, so I'll loosen the rockers that rotated and will try to be absolutely sure that I'm on the base circle of the cam when I re-tighten them. I suppose it would be a good idea to double-check the ones that didn't rotate too so I'll do that as well before I start it. It'll be a few days before I can work on it again because of Thanksgiving but hopefully I can finish this up this weekend.
Melting Slicks
Joined: Nov 2009
Posts: 2,922
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From: West Branch, MI
If you simply tighten down all the rockers to the correct torque with the heads removed, you would not have any of these issues... correct? I do realize that the original question was dealing with the heads while they were on the motor. Also, this is not any sort of inflammatory remark..I'm simply trying to learn more and more about engine assembly and wanting a more workable knowledge... Thanks for making me think and learn.