Can I "borrow" rocker arms from my '65 273 for my '71 340?

RustyRatRod said
Really? I have seen adjustable rockers with hydraulic lifters take anywhere between a 7.05" to an over 7.5" pushrod. No way in the world I would try it without measuring first. Just too many variables, not the least of which was Chrysler's absolute terrible deck height finishing. Most were way too high.

Then, throw the engine's history in the mix.......you're talkin about up to a 50 year history. No telling what machine work has been done previously, what thickness head gaskets, what lifters you're using......and on and on.

The optimum adjustment is to have between 1-3 threads protruding through the rocker arm on the pushrod side. With too long a pushrod, there is the chance that the top of the pushrod cup will contact the rocker and result in broken parts.

With too short a pushrod, there is a chance the adjuster ball will break off from too much length with the pushrod having too much angle on it.

No sir. The best thing to do is measure, measure, measure. And get it RIGHT.

The actual measurement for adjuster protrusion (taking into account the rockers have the factory oil hole timing) is 9/32" +/- .020 and the more agressive the lobe the more important this is.

Pushrod length does NOT affect rocker arm geometry per se, as the only thing that controls geometry on a shaft is the relationship of the valve to the height of the stand, and the rocker itself. Lift factors in, but en talking about correcting geometry, you either raise or lower the shaft, or make the valve longer or shorter. The push rod length just affects how far out the adjuster is.

That said, some rockers have the adjuster at a different angle than OE, so as you screw the adjuster up and down it SLIGHTLY changes the rocker arm ratio.