Packard Forum Index » V-8 (1955-56)

Thanks, HH. You're great! I'll do the fix manana and post back.

FYI, 180 strokes/min.? Laughable! Try 20 or maybe 30.

No problem - hope all works out. Great looking car by the way.

It might not be a bad idea to replace all your vacuum hoses while you're at it. If one was brittle and broke apart, others might be cracked or loose and causing your low or loss of vacuum. IIRC, the amount some others mentioned having was around 14-15" of vacuum on that engine.

I had noted earlier in a post on my 56 Caribbean that I was only observing about 14-15 inches of vacuum at idle. But subsequently, rebuilt carburetors and a very thorough tuneup got that up to about 19.5 inches. This a 90,000 mile engine. On high speed (not the reduced arc) my vacuum wipers are at least as fast as the electrics on my new Lincoln, and faster than you would almost ever need except in a monsoon rainstorm. Yes, they slow down but almost inperceptibly when you give it the throttle but are still quite fast. I used Mobil Vaccum Pump oil to lubricate the motor.

Thanks for the extra replies. How are you meassuring inches of vacuum? As of this morning, my wipers are dreadfully slow again.

Also, I don't want to ask too much, but if anyone is inclined to lay-out this vacuum theory and how it works in practice in detail, I'd be most grateful. I'd like to know how it all works, so that when you talk about tune-ups and carburetors improving vacuum, I will know why. I have no clue.

Vacuum is measured with a vacuum gage and taking the reading from any convenient port on the intake system, manifold or carburetor base, but since on the V8 Packards there is a secondary vacuum source, the mechanical vacuum pump, you want to eliminate this as a source first. You can mount the gauge to the vacuum line that exits the base of carburetor and goes to the junction block near the wiper motor; just pull off the hose to the block and slip the gauge over the metal tube. Or you can remove the vacuum brake booster check valve and measure it there.

The wiper motor is a simple vacuum motor comprising a pivoting paddle; vacuum will draw the paddle to one end of it's travel which trips a valve which then admits the vacuum to the other side and draws it back. Pretty basic. If you need your wiper motor rebuilt, no one is better than Ficken out on Long Island. About $60 lsst time I looked.

Perhaps someone will recommend a good primer book on general automotive principles and repair for you to read. I grew up with Glenn's Auto Repair which is nothing short of superb, from basic principles to detailed overhaul. But it's been out of print for a long time. Motor's Manuals of the era can be useful but don't give much on principles and theory.

I see what you are saying and pretty much understood that was the idea. What I was looking for was sort of a step by step detail. Kind of like:

1. When you turn the knob at the dash, it moves the motor to engage the wiper control device. Even, though it is a vacuum system, the motor is necessary because it does X or Y.

2. The reason there are vacuum hoses from the control knob at the dash is because when you turn the knob, bla, bla, bla....

3. A vacuum is pulled through the manifold because when the car is running, such and such does such and such, and as a result, a vacuum is created.

If I sort of got how you get from Point A to Point Z, then, I could use that knowledge to help me deal with my other cars, like the '53 Buick I have. I am sure they are pretty much the same. They might be slightly different, but if I knew the purpose and operation of each component in the chain, I would have it pretty much down.

You're really asking for a lot here! I'll try but keep it brief, maybe others will come along and elaborate. When you turn the dash knob, you're not turning the motor, you're opening a valve on the vacuum motor which admits vacuum to the motor to allow it to operate (oscillate) the motor paddle back and forth. The blades are moved by a cable and pulley arrangement attached under the dash to the motor output shaft. The dash knob operates the valve on the wiper motor via a small bowden-style cable.

The vacuum comes from the downward stroke of piston with both engine valves closed. The vacuum is required to pull gasoline from the carburetor. The openings in the carbs are small compared to the piston diameter and thus you create a vacuum, each piston in turn doing the same thing to maintain a more or less constant vacuum. Think of pulling the plunger down on a syringe; it creates a vacuum to permit liquid to be drawn in via the needle tip. . That manifold vacuum powers your wiper motor, the washer, the power brake booster, and regulates the distributor ignition timing at certain power situations.

I didnt happen to notice, but have you taken a careful look at the vacuum block (where the vacuum lines from the vacuum pump and carburator hook up? mine is cracked, and it took me awhile to find it. my wipers barely moved some days, and other days, they worked about 30%.

Owen

that was a good primer, but i believe, the vacuum occurs with the intake valve open. the vacuum is created beneath the throttle plates, which is why vacuum drops when the throttle is opened.

A fine point, thanks for noting, and perhaps i should be been more detailed. I believe the intake valve opens after the piston has begun it's down stroke, but of course the inlet valve is what permits the vacuum, which can only be created by the downward movement of the piston in a semi-closed enviroment, to move from the cylinder to the intake manifold and then the inrushing air to fill the vacuum lifts the gasoline from the carb jet within the venturi(s) if the throttle plate is open.

The vacuum is partially trapped within the intake manifold and cylinder by the closed throttle plates, which is why (1) carburetors need an idle circuit, and (2) why the vacuum drops when you open the throttle.

I think we're saying the same thing, but differently.