Rocker Arm R&R - The 1947 - Present Chevrolet & GMC Truck Message Board Network

farmerfred · 11-16-2006, 07:55 PM

I'm hoping that the precipitation will stop soon so that I can remove the rocker arms and push rods on my 1972 C-20 to see whether they're the cause of the ticking sound. The shop manual is straightforward on this. The online manual at AutoZone adds this:

Install the rocker arms for each cylinder only when the lifters are off the cam lobe and both valves are closed.

Does anyone know whether I need to do this? I don't see why, and would like to know if that's what I need to do.

Thanks in advance,

Jayss109 · 11-16-2006, 08:06 PM

this is to set the proper preload on the lifters
________
ZX14 VS HAYABUSA

farmerfred · 11-16-2006, 08:17 PM

Thanks, Jayss109. I was hoping I it was easy. Should've known. Well, how do I know when the lifters are off the cam lobe and both valves are closed?

stllookn · 11-16-2006, 08:27 PM

YUP...it is important. Tolerance on your lifter adjustment is critical. The only time the lifters are free of the cam is when the particular cylinder is at TDC. Even mild cams have overlap between exhaust and intake so 360 out from will TDC (ignition) will still have some cam contact with the lifters. Hydraulic lifters are .021 in. - .042 in. Solids are quite a bit tighter. Overlap on my cam at 360 out from TDC is about .048 on exhaust and .030 on intake. That would be way loose on both and would result in noisy hydraulic lifters at TDC.

bullwinkle · 11-16-2006, 09:48 PM

Before I figured out how to adjust them right, I bent a few pushrods.

Here's a good link on valve adjustment.

http://www.centuryperformance.com/valveadjustment.asp

11-16-2006, 07:55 PM	#1
farmerfred Registered User Join Date: Mar 2006 Location: ohio Posts: 66	Rocker Arm R&R I'm hoping that the precipitation will stop soon so that I can remove the rocker arms and push rods on my 1972 C-20 to see whether they're the cause of the ticking sound. The shop manual is straightforward on this. The online manual at AutoZone adds this: Install the rocker arms for each cylinder only when the lifters are off the cam lobe and both valves are closed. Does anyone know whether I need to do this? I don't see why, and would like to know if that's what I need to do. Thanks in advance,

11-16-2006, 08:06 PM	#2
Jayss109 Active Member Join Date: May 2005 Location: San Jose, CA Posts: 235	Re: Rocker Arm R&R this is to set the proper preload on the lifters ________ ZX14 VS HAYABUSA Last edited by Jayss109; 04-27-2011 at 11:42 PM.

11-16-2006, 08:17 PM	#3
farmerfred Registered User Join Date: Mar 2006 Location: ohio Posts: 66	Re: Rocker Arm R&R Thanks, Jayss109. I was hoping I it was easy. Should've known. Well, how do I know when the lifters are off the cam lobe and both valves are closed?

11-16-2006, 08:27 PM	#4
stllookn Saving 1 truck at a time! Join Date: Aug 2001 Location: Kent, WA Posts: 6,465	Re: Rocker Arm R&R YUP...it is important. Tolerance on your lifter adjustment is critical. The only time the lifters are free of the cam is when the particular cylinder is at TDC. Even mild cams have overlap between exhaust and intake so 360 out from will TDC (ignition) will still have some cam contact with the lifters. Hydraulic lifters are .021 in. - .042 in. Solids are quite a bit tighter. Overlap on my cam at 360 out from TDC is about .048 on exhaust and .030 on intake. That would be way loose on both and would result in noisy hydraulic lifters at TDC. __________________ '68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary)

11-16-2006, 09:48 PM	#5
bullwinkle New Member Join Date: Jun 2006 Location: Regina,Sk, Canada Posts: 30	Re: Rocker Arm R&R Before I figured out how to adjust them right, I bent a few pushrods. Here's a good link on valve adjustment. http://www.centuryperformance.com/valveadjustment.asp



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