283 2 bbl line from carb to back of block?

[canadian_diesel1964]

I just removed a large vacuum type line from the back of the 2 bbl carb on my 63 283. The line went to a rubber grommet at the back of the block just aft of the manifold. Is this a vacuum line? Or a vent line? It had a huge crack and hole in it the size of a dime so I think it wasn't doing anything...thanx guys I don't know the 283 that well at all.

[markeb01]

When the engine first designed, there would have had a "Road draft tube" in the hole behind the intake manifold. Here's an example:

http://www.lategreatchevy.com/chevy-...1958-1962.html

As the vehicle traveled down the road, a "draft" (low pressure area) was created at the bottom of the tube which drew fumes out of the crankcase.

With the development of positive crankcase ventilation (PCV), the road draft tube was eliminated. Initially an adapter was bolted in the draft tube hole in the block, and a hose ran to a PCV valve and on to the base of the carburetor.



As these adapters are now very hard to find, many owners stick a valve cover grommet in the block hole, insert a compatible smog valve, and run a hose to the carb base. Any of these arrangements will work, provided there is either a breather cap on the oil fill pipe, or one (or both) of the valve covers.

[Captainfab]

Here is another current thread regarding the crankcase venting of the '67 and earlier small blocks.

http://www.67-72chevytrucks.com/vboa...d.php?t=666223

[canadian_diesel1964]

Thank you gentlemen!