Hole "A" is for the road draft tube since 283's were made in the pre-PCV days. Hole B is for a vent canister that prevents liquid oil from being splashed out of the draft tube. It's about 2" in diameter and 6" long, with baffles, similar to the vent tube on the side of a stovebolt six. Instead of a road draft tube, there was an adapter made to convert to a PCV valve. The PCV attached inline with a couple of 3/8" diameter vacuum hoses, one to the adapter, and the other to the intake or the base of the carburetor. You can probably find a vent canister on Ebay.

Edit: The canister is available, GM part number 3728502, but it's pricey. Here's a link:

https://enginbearin.com/3728502

There's also a couple on Ebay today. With a little bit of fabrication skill and some exhaust tubing, it would be possible to make one- - - -it's VERY low-tech!


If you can post a photo of the end of one of the 283 cylinder heads, we can probably make an educated guess about the compression ratio, valve sizes, and the type of carburetor it's supposed to have.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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