Question About Difference In Pulley Diameter?
 

I have a couple of 402's and both have power steering pulleys. The one in my truck now (original '72 engine) has a power steering pulley that is the same diameter as the other crank pullys. The one I am putting in (1971 engine) has a pulley that is about 1" in diameter smaller. Could this possibly be one for a higher revving engine? The pushrods in the '71 engine are 3/8" dia. and has valve springs that have inner damper coils. My orig. engine has 5/16" pushrods and single coil springs. I am curious about this. I will put my original P/S pulley on the engine I am putting in my truck and will figure out what to do with the other.

btt

If you have dual springs, there is an aftermarket (or a huge stock) cam in it. Not typical stationwagon/truck motor. The pully is probably G.M.'s way of cutting costs and using a 'universal" pully that fits 5 models instead of one part number per model.
Just a guess on the pully, but it makes sence.

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Both of the 454s that I had for my truck came stock with dual springs. Granted, they weren't stock motors for the truck, but I don't think it was uncommon for big block GMs to have dual springs. Both had 5/16 hardened pushrods and guideplates.