Re: ZZ4 Distributor
NO, NO, NO, NO......NO, NO on the curve kit, they do not work.
The 41 weights and 375 center plate are what the ZZ4 wants, they are fine, do not change them.
Those curve kits are NOT for street use, they are designed to eliminate the vacuum advance, and add excessive INITIAL degrees for DRAG RACING ONLY, NOT FOR STREET USE. The springs are fine, but not the weights/center.
The shims in the first selection on the link are fine for the large HEI.
As far as the upper shim I use, hardware store, and take th shaft and reluctor with you. I use a very thin diameter red fiber washer that fits all the way up into the under side of the reluctor to help alleviate the excessive end play, then complete the end play setting with the steel shims on the bottom of the shaft. End play, between .015 and .019. DO NOT STACK SHIMS SO THICK THAT THE ROTOR DOES NOT SPRING BACK FREELY. This is why we still want .015 plus end play, so the "stack" doesn't lock up the mechanical advance.
There is another reason as well, in the distance the gear is set by adding the steel shims, and the fiber washer. Most large HEI have upwards of .090 end play. Setting the end play distance with shims only on the bottom of the shaft, sets the gear, and OIL PUMP DRIVE SHAFT END FURTHER DOWNWARDS into the engine, moving both closer to the oil pump drive shaft. Too much shimming downward can possibly stack the distributor shaft, intermediater shaft and oil pump gear solid, and holding the distributor body too high to let the stack be loose. In that case, you'd need the second set of shims shown on the link, to raise the distributor body up to allow no stack on the oil pump drive setting.
Now, to those that tell me I am a moron for using a fiber washer under the reluctor, UH-HUH, Yup, OK, tell me why. Well, I KNOW why, Chevy, some Cadillac and AMC, and Buick Delco-Remy distributors rotate clockwise, and THRUST UPWARDS, so, there is no tension, nor wear stack on the fiber washer under the reluctor. Olds, Pontiac, and some Cadillac rotate COUNTER CLOCK WISE, and thrust DOWNWARDS, putting rotating tension on the fiber washer.
So, hardware store, thin wall red fiber washer, .030 or so thick, then set the end play to what I said before, and always check the shaft stack when installing the distributor, to make sure the oil pump drive isn't hard stacked, either.