'56 Olds Intake Manifold question

[Guest]

I am in the process of rebuilding a '56 Olds Holiday. While cleaning up the engine, 324 4bbl, I noticed a hole/port in the bottom of the intake manifold. It looks as if there was some type of line that may have been connected.

Since the hole/port in the intake is right above the valley cover, I have doubts about a vaccum line connecting here. Can anyone tell me what this hole (port) was for or where it should connect. All advice will be greatly appreciated. :

[rocketraider]

I think what you're seeing is the lower end of the choke hot air tube. Try blowing air thru it and see if the air blows out the tube at top of intake manifold, where the choke tube connects to it.

If it's rusted out (many are), one can probably be fabricated from steel tubing. If there's no tube in there, you'll have an exhaust leak.

[Guest imported_pete324rock]

The only other thing I can think of is -I recall there might have been a threaded plug at the very underneath of the manifold which is sometimes removed when hot tanking to boil out rust.If you still don't know I have one I can take a look at-just gotta dig it out a bit -no real problem-Imade a new steel tube and it was a peice of work with the different taper to it but hopefully will ensure a smoother running car-every piece is important!

[Guest]

Thanks. Here's a little more information. The hole/port I'm referring to is on the driver's side, the bottom of the center cross-over and has what appears to be an insert tube similar to the choke heat riser tube.

I plan to insert a metal tube and route it out of the bottom of the intake so I don't have to pull the manifold off later. Do you know if this is necessary or should I just plug it off?

Thanks in advance.

[Guest imported_pete324rock]

Sorry for the late reply but usually I get a notice in my email that someone has responded-perhaps you didn't reply to me personally.Anyways I just went in the basement to look at a spare 4 barrel that I have which surprisingly has the tube in perfect shape-so this is how it goes......that piece of casting that you are talking about on the drivers side is the end of the tube that starts open to the outside air and follows thru the middle exhaust ports all the way to the other side where it comes up to attach to the choke tube.If that tube is missing The exhaust will pass thru that hole that you intend to block off.The idea is to warm the air up but not be exposed to the exhaust gasses.If you have the manifold off,I would fix it right-yesterday I saw tube kits on ebay for a couple of bucks-check application though-enter 56 oldsmobile in search but be sure to check box under search.."all descriptions" you'll get 14 pages but lots of stuff slip thru because of selective headings....or just make your own like I did--make sure heat riser is working as well--they all work together for ecomomy as the book says...pete