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Re: bent pushrod

To: Arnie Sugar <asugar@hwageo.com>, "Tiger's" <tigers@autox.team.net>
Subject: Re: bent pushrod
From: Craig Wright <cwright@pdghightower.com>
Date: Mon, 24 Jun 2002 15:13:31 -0700
Early 260, and 289 (pre '68, I think.) used a ball and socket type
rocker arm and the arm was prevented from moving by narrow push rod
holes in the head. These holes act as sort of a guide plate. Later heads
had larger push rod holes and used what is called rail rocker arms to
prevent rotation of the rocker arm. These arms have small ridges on the
side of the rocker arm that comes in contact with the valve stem. These
ridges extend down the side of the valve stem .040" or so and prevent
the arm from twisting. A problem occurs if you mix up these two systems.
I had a 289 rebuilt years ago with that problem. It went about 3000
miles before a rocker arm became askew and bent a push rod. 

Craig Wright
 


Arnie Sugar wrote:
> 
> Oddly enough, I had the same power loss/rough engine thing just happen,
> and it was the fuel filter.  However, that was just a warmup for things
> to come...
> Last week I heard a loud top end knock, which upon removing the valve
> cover turned out to be a bent pushrod and rocker arm askew on the valve.
> Of course its on the #8 intake, the farthest one back, the only one that
> can't be installed with the heads/motor in place? or are there any
> tricks for this?  Small comfort, I could get the bent rod out.
> Any ideas on what would cause this, what to look for, how far to tear
> down, etc?  I'd like to know what caused it before just replacing the
> pushrod, no? Should I pull the head off ?  I inspected all the other
> pushrods on that side, #7 intake was also bent, but the rocker was still
> aligned.  Details - it's a 289, with only 3000 miles on it, albeit
> rebuilt around 15 years ago, with a Crane cam, hydraulic lifters, chrome
> moly TRW pushrods, and it burns some oil (I always suspected the engine
> didn't break-in properly - not sure if this could be related).  I'm a
> bit rusty, as I haven't opened up a V-8 in over a decade.
> Arnie

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