The 1947 - Present Chevrolet & GMC Truck Message Board Network

The 1947 - Present Chevrolet & GMC Truck Message Board Network (http://67-72chevytrucks.com/vboard/index.php)
-   Engine & Drivetrain (http://67-72chevytrucks.com/vboard/forumdisplay.php?f=24)
-   -   Loose Rocker Arm (http://67-72chevytrucks.com/vboard/showthread.php?t=623471)

CB1987 04-02-2014 09:07 PM

Loose Rocker Arm
 
I've been hearing a tapping in my engine at certain RPMs since my 350 had a full rebuild from acertified mechanic . Brought it to him and he said it was just something loose but not involving the engine. After checking every nut and bolt I did some research. Came up with the valves needing to be adjusted. I popped off the valve cover to see if it is something I could do. Going through and wiggling the rocker arms, about 50% of them were able to move with little force. Since I have a warranty I figured I would leave it to my mechanic. Sorry for the long breakdown but they should all be equally tight regardless of the position of the pistons right? Thanks for the help!

cableguy0 04-02-2014 09:15 PM

Re: Loose Rocker Arm
 
Yes they should all be tight. If you have that many rocker arms loose I would bet on a cam that's wiping out. I would be especially concerned about the cam If this problem has gotten worse over time. Was the engine broke in properly with the proper oil for a flat tappet cam? Was a zinc additive or the proper high zinc oil been used in the engine? You can also check to make sure the studs aren't pulling out of the heads.

siggyfreud 04-02-2014 09:58 PM

Re: Loose Rocker Arm
 
Do your rocker arms have posilocks? When I first installed aftermarket rockers I didn't properly understand how the posilocks worked, and thus my rockers all started to chatter and become loose until I read about how to adjust and lock them down.

They look like this: http://img.auctiva.com/imgdata/5/0/7...0350277_tp.jpg

If memory serves, you adjust the rockers to their proper tightness, then crank down on the inner lock, and then do 1/4 or 1/2 turn on the outer nut. This locks them into the proper tightness.

68post 04-03-2014 11:09 AM

Re: Loose Rocker Arm
 
Quote:

Originally Posted by siggyfreud (Post 6608957)
Do your rocker arms have posilocks? When I first installed aftermarket rockers I didn't properly understand how the posilocks worked, and thus my rockers all started to chatter and become loose until I read about how to adjust and lock them down.

They look like this: http://img.auctiva.com/imgdata/5/0/7...0350277_tp.jpg

If memory serves, you adjust the rockers to their proper tightness, then crank down on the inner lock, and then do 1/4 or 1/2 turn on the outer nut. This locks them into the proper tightness.

NO, sorry but you set the outer nut with the wrench and hold it still and then (while holding the outer nut still), set the inner set screw tight the hold the setting.

Marv D 04-03-2014 02:23 PM

Re: Loose Rocker Arm
 
Quote:

Originally Posted by siggyfreud (Post 6608957)
....., you adjust the rockers to their proper tightness, then crank down on the inner lock, and then do 1/4 or 1/2 turn on the outer nut. This locks them into the proper tightness.

That's a receipie for a broken rocker stud. DON'T DO THAT!!! The stress it puts on the threads, along with the hammering of the cam on a stiff valve spring.... The stud will snap right at the bottom of the nut..

Like 68post suggests,,, set the preload and set the polylock with a allen wrench WITHOUT TURNING THE ADJUSTMENT.

And I agree, cut your oil filter open and see if it's loaded with cam debris. If so,, just get yourself a hoist and get started plling the motor. Bearings are trashed, oil annuluis are all full of debris.. If you just change the cam, you just eat it up wit hthe ground metal in the engine. Bearings are soon to follow.


All times are GMT -4. The time now is 07:41 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com