Re: 51Packard's....51 Packard

Posted by Mike On 2011/6/20 20:15:01

I can speak to the tube, the choke tube pokes into the top of that inner choke tube. When the air is drawn through the hole you asked about up through the top where the choke tube pokes in, it is heated before it gets to the choke tube piece that connects to the carb. That's the choke air inlet, if that makes sense.

The choke doesn't suck in exhaust air directly, it would clog the choke up mighty quick. Rather, exhaust gas heats that tube up and when air is passed through the center, it gets hot. The choke is pulling clean engine compartment air in slightly and it gets passed into the carb after going through the choke housing. No exhaust air should be touching any fresh air or choke parts unless that inner tube that's pressed into your exhaust manifold is rusted through, and then it needs replaced as you'll have an exhaust leak AND overheat the choke and clog it with soot.

Not sure about your 51 as i have a 50, the only vacuum connections were one on the carb for the dist timing advance, and one fitting near the front for wipers. I read a TSB that they moved the wipers one to the base of the carb to solve some rough idling when the wipers were on, i'm assuming it would over-lean the one cylinder the port is over if the wipers were active, and moving it distributed the extra incoming air over all cylinders.

The 4bbl manifold (53) i just put on has no fitting in the front, but a big one out of the intake manifold beneath the carb base out the rear, and again, one out the base of the carb.

Edit: where your petcock is, that's where the wiper pump "outlet" goes, it pumps air from the wipers and into the manifold, and the pump is a pass through at low rpms, the manifold draws the air in itself. It was a little brass-ish elbow on my manifold, and looks original.

You should be able to run a pipe cleaner through the choke stove tube, or see through it. If you plug one end and blow in the other, you shouldn't have any leakage or hear it leaking into the exhaust manifold.

I highly recommend:


Separating the manifolds

Having them both blasted with somewhat normal or gentle media

Coating the exhaust with something like POR-15 manifold grey

Painting the intake with something like dupont black engine enamel

new hot spot gasket with copper gasket spray

Bolt them together loose, square them up, and tighten them together tight.

Check the block face with a straight edge and have them milled together so they're flat.

No leaks, and will look great! Just did 2 sets of manifolds like that and they came out awesome.