Tapping Under Valve Cover
01-20-2003, 11:53 AM
#1
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Car: 1978 Chevrolet C10
Engine: 350
Transmission: Turbo 350
Tapping Under Valve Cover
well i have had a tapping noise for the life of my engine which just turned over 1k. it has always had a tapping in the passengerside valve cover. i think that the lash was never set properly on a rocker or something of that sort, so i was wondering if anyone could dig out some TQ numbers i am soposted to TQ the nuts to, and what degrees for the feeler gauges. thanks for any info.
01-20-2003, 12:00 PM
#2
If it is a rocker arm I can't tell you the presise torque amount. What I can tell you is that most people do it by ear. That I know of.
Open the valve cover and reinstall the gasket. (So oil doesn't go all over the place to much.) While the car is running find the offending rocker arm and tighten it down until you can not hear it anymore. Then give it one more quarter turn to lock it down.
This proceedure was given to me when I had this same problem.
Although on my car this turned out to not be the problem. It turned out to be a lifter. Hope this helps.
Open the valve cover and reinstall the gasket. (So oil doesn't go all over the place to much.) While the car is running find the offending rocker arm and tighten it down until you can not hear it anymore. Then give it one more quarter turn to lock it down.
This proceedure was given to me when I had this same problem.
Although on my car this turned out to not be the problem. It turned out to be a lifter. Hope this helps.
01-20-2003, 02:23 PM
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Car: 84 Z28
Engine: 355
Transmission: 700R4 with corvette servo
I had the same sound, only it turned out that my header bolts were loose and I blew a small hole in the header gasket. Replaced the gasket and tightned the headers down, now no more noise.
01-21-2003, 08:18 AM
#4
Squeeks,
The procedure all depends on which engine you have.
Pontiac V-8 engines used a torque specification and allowed the lifters to compensate for valve lash. Chevrolet V-8 engines use a "turns after zero lash" setting instead of a torque specification. You need to get the engine to operating temperature, remove the rocker cover, restart the engine, back off the rocker adjusting nut until you get obvious lash (tapping), then tighten the nut slowly until the lash is gone. Tighten an additional 1/4-1/2 turn beyond that point, and it's all set.
The procedure all depends on which engine you have.
Pontiac V-8 engines used a torque specification and allowed the lifters to compensate for valve lash. Chevrolet V-8 engines use a "turns after zero lash" setting instead of a torque specification. You need to get the engine to operating temperature, remove the rocker cover, restart the engine, back off the rocker adjusting nut until you get obvious lash (tapping), then tighten the nut slowly until the lash is gone. Tighten an additional 1/4-1/2 turn beyond that point, and it's all set.
01-21-2003, 06:47 PM
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Another way I was taught to do this, is when a valve is closed, back off the rocker arm nut until there is clearence between its tip and the valve stem, start turning the pushrod with your hand, while tightening the nut, then as soon as the pushrod hesitates by touching the rocker arm, tighten the rocker nut 3/4 of a turn more, and your set, then turn the engine over and do the other 8. Hope that makes sense.
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