Working Distributor Unit

[grey beard]

I have seen several different distributors in the past few weeks. Seems like there are at least three different body styles with different openings for the vacuum advance arm, different vacuum advances and different breaker plate assemblies, all of which require different contact points. Without exception, every one I have found already has the vacuum advance unit either toasted or blown out - they all seem to leak.

Does anyone have a complete distributor for sale that has an operational vacuum advance unit with it? I seem to be striking out here with all the logical sources and solutions. With all he different applications for flathead engines, can these things be this scarce?

Do all of you have working vacuum advance units on your drivers? Do you know how to check them out? What do the rest of you do when you need one of these things? Pray a lot?

[Reg Evans]

I'll have a look down in my little bone yard. I have a 52 1/2 ton that was running on about 3 cylinders when I parked it. Can you post a photo of that AIR knob and cable for motivation ?

[Young Ed]

Dave when the vac advance went out in my 48 I tried to find a new one. Never did find one. I finally put a used one in that worked at the time. That was a couple years ago haven't verified that its still working.

[billwillard]

I have one with no vac adv from a powerwagon if anyone needs.

[Merle Coggins]

Doggone you Dave. All this talk about failed vac advance units made me get out my vaccum pump tonight and test mine. It pumps up, then bleeds the vaccum off again. I guess mine is bad too. I say it's all Dave's fault. Before all this fuss I was blissfully unaware. :D

I didn't pull the cap to see if it works, even with the vaccum leak, but either way I should probably just disconnect it. I don't need to be driving around with a vaccum leak. I'd probably be better off just driving it without the added advance.

I'm sure I tested it when I built the engine, but either way it's bad now, so I'm in the same boat as you Dave.

Merle

[grey beard]

Yupper, Merle. It's all my fault. Mebby you'all'd a'been happier not knowing you got problems, what?

Can an ostritch drive a pilothouse with his head up his sand mound? Can it be that iggorance really is all that blissful.? Here I tell you'all that i can't find a vacuum advance, and looks now like I started a stempede to find every one incapivity. Go figger . . .

[greg g]

I have a small stash of distributors, and they are all different. I did have two checked on an old distributor machine. Both had working vacuum pots. Both are different numbers, taking different caps point sets etc. I am using the one with that had the least variance from the factory speced advance curve.

It happens to be from a 54 Truck engine, but seems to work very nicely in my 56 plymouth 230 block.

If I had one more, I woudl sed you one, but for know, I will be keeping them as backups. Hope you are able to find one, bu in the meantime, cap off tha vacuum line and drive it.

Good luck in your search.

[Don Coatney]

but either way I should probably just disconnect it. I don't need to be driving around with a vaccum leak.

Is it really a vacuum leak if it is connected ported to the throttle plate on the carburetor, not manifold vacuum? You only lose ported vacuum when the throttle is opened and you also lose manifold vacuum when the throttle is opened. When the throttle plate is closed full vacuum is restored.

[greg g]

not necessarily a vacuum leak but a hole that size would likely lean out the mixture.

[Merle Coggins]

Well, last night I checked the vacuum advance on my parts truck and it checked out OK. But during the test I noticed a slight drop on the vacuum gauge. I found that I had a loose connection. Once I tightened it up it all worked good and held vacuum. So, now I know I have a good spare, but I wonder...

It seemed odd that I could pump up a vacuum and then it would bleed off. If the diaphram was torn I probably wouldn't be able to pump up vacuum. So I went back to the one on my truck and rechecked it. I had a similar issue with a leaky connection at the end of the vacuum advance unit. I removed the plug at the end, cleaned up the surfaces, added a little pipe dope to the plug and reinstalled it. Now it holds vacuum and works perfectly.

So it was all a false alarm and all is well again.

Merle

[Reg Evans]

I discovered the same leak on my 52 last week. Just a loose connection at the VA.

[grey beard]

For now, I am running with the vacuum line capped and no working vacuum advance. Seems to run just fine, but I am sure economy will suffer, etc.

I now have TWO working vacuum advance units but unfortunately both fit another distrihutor type than the one I am using. Most likely I will do my best to find cap and rotor, pts. etc. for this distributor and use it since I now have a usable advance unit for it.

Looking at various distributors, I see some have a ball bearing braker plate that pivots with the vacuum advance signal, while others have a simple pivot point that allows the plate to move with the advance but not on the same center as the distributor cam. I also have three different type of caps - one with the big notch - an inch long - that fits into the corresponding dist. body notch, a second with a very small notch and a third with a halfr inch notch that fits into a pair of ears on one or the cap clamp retainers. Two different rotors - small and large, three different caps, and at least three different body types. Some standardizatio. No wonder those MoPar parts counter men were all a little squirly. Just getting tune up parts was a real homework job, compared to some other brands we all know and love. Go figure.

At present, I have tinkered up a small cap type distributor with a working vacuum advance unit. It tests fine electrically on the bench, and has fine spark at the coil secondary wire, but I cannot get spark to the plug wires for the life of me. Gotta be a cap-rotor issue, but haven't been able to get it working right yet. I'm not going to put it in the engine till I can get it to make spark at the plug wires on the bench.

Any suggestions on this one? Points, coil and entire system work just fine. Hot spark from the coil wire, but nothing OUT of the cap to the plugs.

Bummmmmerrrrrrrrrrrr . . . . . .

[Don Coatney]

Any suggestions on this one? Points, coil and entire system work just fine. Hot spark from the coil wire, but nothing OUT of the cap to the plugs.

Bummmmmerrrrrrrrrrrr . . . . . .

Dave;

Check the spring loaded button inside the distributor cap. Make sure it is moving freely and that it is making contact with the rotor tang. I found that there was a difference in rotors. Some fit further down on the distributor shaft and do not make good contact with the spring loaded button. You can bend the tang up or shim the rotor with a small washer. There should be a shiney spot on the tang where the button rubs it as the rotor spins. If there is no shiney spot but carbon tracing that may be where your problem is.

When I was setting up my new vacuum advance for the correct curve I connected a vacuum gauge to the venturi port on the carburetor. With the engine at idle there the gauge read zero. As I opened the throttle the gauge showed increasing vacuum up to about 17 inches of mercury at around 2000 RPM's. The manifold vacuum reads just the opposite around 19 inches of mercury at idle and zero when the engine is accelerating. When the engine is decellerating the manifold vacuum is over 20 inches of mercury. I set my vacuum advance to full open at 11 inches of mercury. As you know this is done by adding/deleting shims above the vacuum advance spring.

[MBF]

GB-try another rotor and/or another cap. I spent the better part of a morning once trying to figure out why a 4 cyl Evinrude didn't have spark after a tuneup. The problem ended up being the brand new rotor that I bought was defective. Put the old one back in and it fired right off. We looked under a magnifying glass to see what the problem was and couldn't find a thing wrong with it-but it was the culprit. Its the simple ones that get ya. Mike

[grey beard]

My Pilothouse distributor is an IAP-4101, which is the correct unit for my 1948 B1B. I very badly need a vacuum advance unit with its bracket to fit this distributor. I now have another distributor in the engine, and it runs okay, but it is made for a clockwise rotation engine - likely a marine or industrial engine application, and I know the centrifugal advance is not working.

Can anyone suggest a vendor source for this part? The Autolite part number is VC-3147. Don't have the part number for the small attaching bracket. ALl my local parts houses just look at me and shuug their shoulders. Surely to goodness somewhere there must be a viable source for these parts.

Thanks for your time.

[Merle Coggins]

Dave,

Have you checked with Antique Auto Parts Cellar?

http://www.maritimedragracing.com/then_and_now_automotive.htm