Quote Originally Posted by Mempho
I have 56 Ford with a 1972 429...69 heads....some Comp Cams Magnum Roller Rockers and know I will need guideplates and studs. I am not sure which size pushrods to use 5/16 or 3/8. Did Ford switch sizes during a certain year? Why are some 3/8 and others 5/16? HELP!!!!!
All Ford production 429s & 460s came with 5/16" pushrods from the factory. There are all kinds of pushrod diameters, lengths and even wall thicknesses available for engine building because these options/choices are dependent on the final engine application(s).

Whether you need the factory length 8.55" pushrod or not depends on which rocker arms you run. Most all aftermarket rocker arms will require a pushrod length that is different than stock and/or applicable only to that brand roller rocker, in order to establish correct rocker arm geomtery, so if you run the Comp Pro-Magnums as you intend, you will first need to figure out your rocker arm geometry and then order the correct length pushrods.

With roller rockers, you will need to run hardened pushrods with the guideplates, because standard pushrods will be chewed up by the guideplates.

Paul