I have had two others, 250HP that had road draft tubes. This car was built for the CA market; maybe that is why.
I have two cars with '57 283 engines. I made adapters from the draft tube hole at the rear of the blocks to a AC Delco pcv valve to the rear base of the carburetors. One has a WCFB the other is an Edelbrock 500 cfm AFB type. The valve part number is AC Delco #214-2295. Available at parts stores or even Amazon. Both cars have been on the road for years and it's great to eliminate the draft tube mess.
I looked in my 62 factory assemble manual. They refer to PCV systems as "special crankcase ventilation systems". The elbow in the crankcase vent port is 5645835. Road draft tubes are 3790735. Getting a bit OT here but I had to check it out.
@Fogger , do your 283s have stock oil fill tubes at the front of their intake manifold to bring fresh air into the engine? Do either of them have additional valve cover breathers? Your solution might work on my Chrysler Hemi, which has a road draft tube and I'd prefer to not add breathers into the virgin valve covers.
Had an orig 62 340HP Corvette-it had the road draft tube adapter and an in line PVC valve to the back of the carb.
Gary, Both engines have GM intake manifolds, #3844461, and fill tubes with open breather caps. No valve cover breathers.
I just installed a system on a GMC 6 and used the screw in 283 valve under the center carb with a hose to the 68-69 front style oil fill with the sealed cap tube put in the original side crankcase breather/draft tube. That oil fill tube has a 3/8” pipe thread fitting you can use for the hose barb fitting. The rocker cover has the vent/breather where the suction air comes from... works great.
I have given this a some thought; and it came to me why they don’t want you to use the rear port. The idea is to have the oily fumes drawn in as central to the manifold as possible so the fumes will be distributed evenly to all cylinders. By having it at the rear those cylinders will be “rich” so to speak and may be more likely to foul plugs. It would be even worse on a dual quad setup. That being said, I’m putting it in the back of the rear carb to keep things tidy. And with a completely rebuilt engine I’m not too worried about a lot of oily blowby. Thanks for the input everyone
It should be fine to connect it to the place you asked about, as long as that port ‘sees’ Both sides of the primary bores. That is, you want the unburned gasses to distribute to all cylinders, as was mentioned earlier. I just did the same thing on a chevy 3x2 setup, though it’s not on the road just yet. The carb base on the right shows the passage for the port that ‘sees’ both bores in this case. I think the rear port on your 4 bbl will do the same thing, but check it of course. The other photo shows a modified draft tube for PCV. I ran hard lines from there to the rear large port of the center carb and also from the brake booster (tube on the left). I used a brass T (not the elbow in the photo) at the rear port of the center carb.
I put a freeze plug in the draft tube hole that was drilled it for the pvc rubber grommet, then routed to carb.