Re: Use of guide plates on older 462 SBC Heads
James you can pin them, I've run them this way. I've also had several sets modified and having access to a mill cut a set myself. If you go the route of screw in studs you also have the option of using the old style without the hex base, but in that case you can't use guide plates and you can't open up the pushrod holes in the head for 1.6 or larger ratio rockers.
I would certainly have the pushrod holes opened to allow you to change rocker ratios at a later date while the heads are off. Yes once the heads are back on you'll need to measure for the correct pushrod length to buy to have the correct geometry and rocker tip to valve stem contact point. Block decking, gasket thickness, milling heads, cutting rocker stud bosses for screw in studs and guide plates all have affects on what length the push rod should be.
Also don't trust what some of the "How To" books will tell you for how much of the stud boss to cut. I followed one of these the first time and it wasn't enough. As a result the stud sat too high and the rocker ended up too far down on the rocker stud. This is how I came to learn and measure all the differences in the various screw in rocker studs available. GM, ARP, Dorman, Summit, they are all veery different in length, hex base height, base to stud radius fillet radius, and how far down the stud the threads extend. GM is the absolute worst and I'd avoid it. ARP has the thinnest hex base of the 4 mentioned at .211" which is actually a good thing if your rocker is sitting lock on the stud. The others are .219 for Summit, .231 for GM and .296 for Dorman, which makes Dorman a poor choice in my book. GM has the shortest dimension from hex base bottom to the start of the threads on the shaft at .806" but it is by far the shortest stud and because of that I'd never suggest using it, amoung other things that I think make it a poor choice. Dorman and ARP are second to the GM in this dimension at .949" and .952". Overall length from bottom of hex base to top of stud the ARP and Dorman again are top at 1.75", Summit is 1.74", GM is 1.59".
But for strength look at the radius at the stud to hex base and GM only extends .050", while ARP is .185". I'd use ARP for strength, the length, the shorter hex base and they are ready to run with poly-locks right out of the box, unlike GM which needs maching the top flat.
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