I have a 085 dizzy in like new condition (tight shaft bushings). Been playing around with it to see how it works. Hooked up the vacuum advance to my 240 to see if the advance was working.

Looking at the vacuum unit, seems to function correctly with vacuum infront of the throttle (moves with the throttle position). After the throttle (engine side) seems to be activated (pulling the points plate) all the time. Is it correct that vacuum needs to come from infront of the throttle?

If so, on the SUs, I don't see a vacuum port infront of the throttle, but there is bung on the front SU that seems to go infront of the throttle. Can that bung be drilled and tapped for a vacuum port?

What about the vacuum retard dizzies? Before or after the throttle?

Paul

BTW-are the points still available for 0231170085 distributor?

What do you have for a motor?

B20A distributors have too much advance for a high compression B18B, B20B or B20E. Might be OK for a low comp B20B or B20F.

What about the vacuum retard dizzies? Before or after the throttle?

Before.

are the points still available for 0231170085 distributor?

Here they are found in 70's Valiant/Dodge Sixes.

--
Three 164's, Two 144's, One 142 & a partridge in a pear tree.

Stock B18D (I assume it based on the VIN tag, but who knows after 40+ years). The previous owner said the head got harden seats, but who knows about that too.

I'm just playing around with a cheap electronic ignition setup possibility somebody posted elsewhere that keeps the points as a tiggering mechanism. I have a '75 Bosch setup, a Crane XR700 in a 002 dizzy, and I have this dizzy laying around that I want to hook up a HEI 4-pin module to. I like the idea about having the points still available in case the module fails.

I thought I would try each one to see which one I liked better. It's just an exercise for fun. Looks like I can run about 9 different combinations with the 4 setups (including the one that's in it).

Paul

Really makes no difference at all once the throttle is opened 1/10th of the way. Hooking up to the manifold will tend to give you a smoother idle, which really helps if you have an aggressive cam.

Obviously, if you hook to the manifold you need to set initial timing with the vacuum disconnected. I have an advance dizzy hooked up that way on our Amazon with a stock B20E (not an aggressive cam), and it idles fine at ~20BTDC with the vacuum full on. Once the throttle opens, it retards -- and it should -- and then you're on the same curve as if you'd hooked it outboard of the throttle.

I don't know what a 085 distributor is. I do know that if you have a B20B distributor the vacuum unit acts to retard ignition timing. The B20E and F did that as well, and it serves to reduce peak combustion temperature, at the expense of fuel mileage.
There are two sources of vacuum - intake manifold and "ported". Intake manifold will be highest (lowest pressure) at idle and decel. Ported provides vacuum just off idle during part throttle cruise, and a bit at idle. It's source is the region at the edge of the throttle plate when nearly closed.
If yours is a retard unit, don't hook it up at all.
Many Canadian market 240's with single SU's had a dual diaphragm which had advance and retard in the same unit. The retard side was hooked to the intake manifold in those cases, advance to ported.

I have hooked the advance side of my dual-action distributors directly to the manifold
with the following rationale:
I want it advanced as far as will do any good under high speed operation.
Sometimes tend to get knocking (pinking) under hard throttle at low speeds, which
amounts to a low vacuum condition. Therefore less advance at those points helps
without sacrificing the advance under high speed operation.

This is an advance dizzy. So, ported is the answer I thought it would be.

Thanks-

Paul