1942 dual carb manifold with or without vacuum?

[Trackless]

Hi there again from Australia.
I'm no expert, lets get that straight first.
The difference in ported (less) vacuum and full manifold vacuum (more) is the amount of advance at idle or thereabouts. Again there are very good threads re this around--try HAMB.
The fuel pump stuff is that the original early vacuum wipers were very poor performers at hi throttle openings (low vacuum avbl).
The fuel pump assembly was actually two units on top of each other (?). The unit held and operated a fuel pump and a vacuum pump to assist the wipers during acceleration, hi-speed cruise or just going up a steep hill in the rain.
As an aside I'm restoring a '47 Super from the ground up. Chassis is done, discs on the front, power booster to the front only with a Toyota (sorry) twin master cylinder.
I bought a Edmunds twin carby manifold from the States and am awaiting my second carby from overhaul. It will look pretty bloody good I feel, all on a fully rebuilt engine.
The car has been in my family since 1949.

Regards

Trackless

[raycow]

I don't recall posting a pic of my engine, but you are right about the line from the intake manifold to the pump.

Buick used two types of fuel pumps, single action and double action. The single action has only a fuel section and has no vacuum lines connected to it. The double has both a fuel and a vacuum section. A line runs from the manifold to the "out" port of the vacuum section and another line runs from the "in" port to the wiper motor. This was done to get better wiper performance when you open the throttle - the wipers don't slow down quite so much (but they still slow down).

If you have a single action pump (no vacuum section), just connect your wiper motor directly to the manifold.

Ray

[bruno]

You always come through Ray. My car is a rat rod. I have dual Stromberg 97's for carbs, a Buick 1942 compound manifold, a freshly rebuilt Straight 8 engine with pistons bored on a 53 Buick Special. I run straight linkage, stock distributor, with no windshield wipers.

What brought this post on, I'm in the middle of installing my intake and exhaust manifold gaskets. In the process of installing my vacuum line on the intake manifold I sheared the vacuum line. Hence my curiosity to poke around the forums and do some research on vacuum or no vacuum.


Just so I'm correct here, in my particular car, I can cap the vacuum port on my Buick 1942 compound manifold and connect the very same vacuum line from my stock distributor to my Stromberg 97?

I do not believe any of the Stromberg 97s have vacuum ports.

[Brooklyn53]

Just a quick update on this topic. I purchased a 1 inch carb spacer with a vacuum port to resolve getting vacuum from my Stromberg. The problem I encountered, with the 1 inch spacer, both gaskets and the carb base, a 2 inch carb stud is a tad too short for the nut to get onto the stud and a 3 inch carb stud is too tall and strikes the side of the carb body. Ideally, the 3 inch carb stud will need to be cut to 2 1/4 inches to allow the nut to thread onto the stud.

[raycow]

Just a quick update on this topic. I purchased a 1 inch carb spacer with a vacuum port to resolve getting vacuum from my Stromberg. The problem I encountered, with the 1 inch spacer, both gaskets and the carb base, a 2 inch carb stud is a tad too short for the nut to get onto the stud and a 3 inch carb stud is too tall and strikes the side of the carb body. Ideally, the 3 inch carb stud will need to be cut to 2 1/4 inches to allow the nut to thread onto the stud.

Would you like the bad news first or the good news?

Ok, the bad news: If you connect your vacuum line to a spacer below the carb, you will get full-time vacuum, not ported.

The good news: If the stock carbs don't have a distributor vacuum port on them, this would have to mean that the distributor is happy with full-time vacuum.

If you still want to run the spacer anyway, it would probably be easier just to cut the length stud you need from a piece of allthread. Studs made this way won't have a shoulder to stop on, so you might want to locktite them in place.

Ray

[telekenfun]

I do not believe any of the Stromberg 97s have vacuum ports.

I just came from my stash of Buick carbs.I have a complete compound setup. The factory Strombergs for the 248 compound intake are Aerotype AAV 16 (primary) and AA 1 (secondary).The Aerotype carbs are a Stromberg refinement of the EE type carbs of the 81/84 97 family .Areotype carbs utilize knowledge Stromberg gained developing carbs for the WWII aircraft. They utilize many of the same parts as the EE/97s including jets, powervalves, emulsion tubes, etc. The qreatest difference is the balanced float chambers that reduce flooding, vapor lock, etc.Aerotypes have refined intermediate nozzles and circuits for smoother transition to the main jet circuits which the EE/ 97 carbs lack. I removed the entire setup with all the lines intact so I'm confident in this information. The primary carb has vacuum ports, the secondary does not. A more detailed description of the AAV 16 will benefit our understanding of how the factory vacuum advance was intended to operate. The "V" indicates a vacuum feature which the AA 1 lacks. The vacuum port is located upstream approximately3/32" from the intermediate emulsified fuel ports. Both these ports are above the throttle plate when throttle is closed or at idle. Resulting in no port vacuum. As the throttle is slightly opened air rushes past these ports creating a venturi action (siphon) on both the intermediate ports and the vacuum port. The siphon action is no different than the action of an old siphon pot spray gun drawing paint up to the spray nozzle. This occurs with air as well as liquids. The vacuum generated is velocity dependent and not volume dependent as the vacuum the pumping action pistons generate. As the throttle is opened more, the venturi effect diminishes and results in reduced intermediate emulsified fuel and vacuum to the distributor vacuum canister. So we can deduce that Buick intended to have little to no vacuum at idle or closed throttle which wouldn't be possible with manifold vacuum. However when an engine is in an open throttle and high volume condition (winding it up) it is possible the velocity past the vacuum port could cause distributor advance while manifold vacuum is quite reduced. This could cause the onset of pre-ignition and pinging. Utilizing manifold vacuum to the distributor would avoid this. If pinging occurs with ported vacuum upon acceleration a switch to manifold vacuum will reduce it. However, manifold vacuum can generate enough distributor advance while cranking to make for hard starting. If you need ported vacuum switch to Aerotypes instead of 97s, they are way better and you can use them either way. While the AAV 16 & AA 1 are approximately the same size as 97s, Stromberg made many larger throttle based Aerotypes for other Buick applications. I use a matched pair of AAUVB-267 from I think the big Roadmaster on our Buick. I have switched to manifold vacuum after I studied all this and it improved the pinging during part throttle acceleration but it's only part of the timing solution. Hope this helps somebody. KB

[39CENT]

I agree [I think?] with this post. we have to remember that at some point as the butterflys open the ported vacuum and manifold vac merg and also all vacuum decreases to zero quickly with throttle opening, manifold vac isnt always 'full time' and the mechanical advance takes over. anyway thats my 2 cents worth for now gggg.