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Re: [FOT] TR-4 pushrods

To: "Tim Murphy" <>,
Subject: Re: [FOT] TR-4 pushrods
From: "Jack W. Drews" <>
Date: Mon, 10 Jul 2006 12:06:21 -0500
I don't know if anyone else has contributed their wisdom on pushrod 
length, but here is my understanding of it.

Theoretically, at half lift, the valve tip, the center line of the 
rocker shaft, and the pushrod end should be in a straight line.

So looking at the rocker position, one end at a time............

The alignment of the valve stem and the rocker shaft are determined 
by the valve stem length, the depth of machining for the valve seat, 
and the height of the rocker stands. The alignment is achieved by 
making the rocker stands taller or shorter. (Note -- with roller 
rockers, it is proper to have the centerline of the roller horizontal 
to the rocker shaft centerline, rather than having the contact line 
of the roller in line with it).

At the pushrod end of the rocker, this means that the centerline of 
the ball should be aligned with the centerline of the rocker shaft.

Pushrod length has no effect on alignment on the valve side of the 
rocker. The length of the pushrod depends on how much has been taken 
off the head and how much has been taken off the cam base circle by 
the regrinding. To make it theoretically correct, you must assemble 
the engine, position the valve halfway down, and measure the length 
required for the pushrod. This is done with an adjustable pushrod. At 
the valve end, the spring is replaced by a very light one to make the 
operation easy.

In real life, some builders go to all this trouble to measure the 
pushrod length, but many do not. Many just look at whether or not the 
adjusting screw is reasonably centered in the rocker, so that there 
is enough for the adjusting nut on the top and no interference of the 
pushrod on the bottom. Interestingly, it is often the case that about 
the same amount is milled off the head and is ground off the camshaft 
base circle, in which case, a stock length pushrod is just fine.

At 10:26 AM 7/8/2006, you wrote:
>Question on pushrods.  etc........................................
>===  Help keep Team.Net on the air

uncle jack 

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