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Old 07-12-2008, 09:49 AM
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Vacuum wipers hook-up help?

I have 1951 Stude pick-up and my vacuum wiper motor has 2 fittings on it, I am thinking this is where each hose goes for ea. wiper, but not sure! Iv'e heard best place to run for vacuum is off the intake, where or what fitting or how is this done? I have a 350 chevy stock and 350 carb. any advise would be great, thanks, Dana (I don't care how it has to be run, just want it right)

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Old 07-12-2008, 10:08 AM
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The vacuum source needs to be FULL manifold vacuum. This can come from a fitting that is in the intake manifold or from the base of the carb. Many carbs have two different vacuum fittings on or near the base. One will be 'ported' source and should NOT be used for your windshield wipers. The second will be a full vacuum source and can be used for your windshield wipers.

Many times these fittings are already being used for the modulator valve on some transmissions, the vacuum advance cannister on some distributors, etc. Try not to 'T' into any existing lines. It is best to add another source in the intake. This is easily done (with the intake removed from the engine to prevent any metal chips getting into the engine) by drilling and tapping the intake in the appropriate position with the correct size tap for the fitting being used. Another easier method is to use a spacer between the intake and the carb that is drilled and tapped (or can be) for an additional fitting to be added.

You are probably already aware that when using vacuum wipers that they will stop or at a minimum slow way down when accelerating. They will also speed up when decelerating.
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Old 07-12-2008, 11:20 AM
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My truck has vacuum wipers. The wiper part worked fine and as stated they would slow down or stop going up hill (rain-X works well!). Mine was hooked directly to the intake. There was a factory "plug" that screwed into it in front of the carb.

I now have hidden power brakes as well. No where near enough vacuum for all that with the Y-block (I assume a 350 would be different). I got a vacuum canister from summit and hooked that directly to the intake and from there I went to the wipers and booster.

Seems to work a lot better that way.

Yes..it is all hidden under the cab. Don't need the extra garbage under the hood.

As far as your two fittings...I really have no idea. My wiper motor only had one where the hose goes.
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Old 07-12-2008, 11:31 AM
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Thanks Frisco, and Brian, Frisco would you know why I have 2 hose fittings in my wiper motor? If it needs both to work I guess I would have to tee them together then connect to intake or carb? NOT SURE, Dana
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Old 07-12-2008, 11:49 AM
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I have been thinking about the 2 ports. Is it possible one of them lets air back into the "wiper motor" for some reason?

I don't have a good close up pic of mine...but I can see a smaller "port" on the bottom of mine that is not hooked to anything. I had never thought about it before.

This is the only pic I can see the wiper motor in (before vacuum canister and everything):

http://i64.photobucket.com/albums/h1...n/DSCF0737.jpg

Hopefully, you can sort of see the second port in the middle of the motor toward the bottom of the square block.
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Old 07-12-2008, 12:14 PM
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I was going to suggest a vacuum canister , but someone brought that up. It does help. I would venture a guess about the 2 ports, but just from recollections of older cars( including a Stude) I've owned. Some had a vacuum side on the fuel pump, with a line going up. I never really analyzed how they were plumbed, but I'm sure it was to lessen the loss of wiper action when accelerating. Most of the vacuum wipers I've worked with lately only have one port, so that is my only guess. Although it could be a vent as was suggest, most times there is a small felt "filter" that serves that purpose. A pic of the wiper unit could help. I will break out my late 40s or early 50s shop manuals and see if I can find anything to add.
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Old 07-12-2008, 12:29 PM
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Brian, nice pic, mine looks like yours but where the port is pointing down on yours, I have 2 identical but mine ore 3 oclock and 9 oclock on each side of my motor. ALSO, I have a 3/8 port at the bottom of my carb, right directly in the center, would this be a full vacuum source to use? Thanks again, Dana
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Old 07-12-2008, 12:37 PM
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According to the early shop manuals I looked at, the 2 ports should be different diameters. They both ran to the original control valve, which has 3 ports with one being the vacuum source. The larger one is the vaccum for operation and the smaller one for parking the blades. I am just guessing, again, since the wipers I've worked on lately have a lever that controls the wiper with park function internal to the wiper motor. But it would seem that the vacuum control unit opens for the operation, through the larger port, and when shut off opens the smaller port line to close and park the wipers. I hope this helps.
Since I am not familiar with that exact system, I would have to think that you could run (if you don't have the original control valve/switch) the larger line only and get operation. However you would have to manually back(using the control valve) the wipers to park when done operating them.
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Old 07-12-2008, 01:14 PM
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Hmm...interesting thread. I never really thought about how they worked.
Mine parks on its own when I turn the switch "off". Maybe there is a line to the valve too, hidden somewhere? The cool thing with vacuum is that they are infinite speed. Just keep turning the switch and they get faster.

As far as I know...mine is now plumbed (plus the vacuum canister) the way the factory had mine. I am aware of the fuel pump/vacuum pump ones being available. I can get one from a Ford FE block (390 and such) that will bolt onto mine and work. As long as the vacuum reservoir works, I will stick with my glass bowl fuel pump.

I have not had mine in the real hills (in the rain) since I installed the vacuum canister, but it definitely improved the brakes a whole lot.

The only rain I have had it in recently was on flat roads. In town and out on rural highway. I had zero issues with the wipers slowing down on that drive, even idling at lights.

Please keep us updated as you get them worked out. I really find this interesting.
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Old 07-12-2008, 01:47 PM
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To me, the best set up for vacuum wipers is a carb/manifold source hooked to a good vacuum canister (check valve in the line and a fuel pump driven vacuum pump hooked to the same canister (check valve installed). You then have a good vacuum reserve when demand is high and supply is low (accleration, the fuel pump vacuum is high and manifold is low: deceleration, the fuel pump vacuum is low and manifold is high) and the canister tends to even out the highs and lows.

My buds 56 Tbird has this set up and it works great.

Trees
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