Model B zenith carburetor vs model A zenith.

[old31]

Is a model B zenith carburetor that much better than a zenith model a carburetor?

Do they produce more power because of the larger diameter air intake? And do they have any other advantages over and model A zenith?

I just got a hold of one and I am not sure I want to install it on a perfectly running other car that I have that was rebuilt By Bert’s.

[MAG]

Yes, Yes, and Yes. ????? If you install, bore out the intake\to match the B carb. to take advantage of the additional power.

[Dave in MN]

Originally Posted by MAG

Yes, Yes, and Yes. ????? If you install, bore out the intake\to match the B carb. to take advantage of the additional power.

If you decide to enlarge the intake manifold, I have some info on my website.
Look on the DYI Help page for a download of how I do it.
Good Day!

www.durableperformance.net

[Charlie Stephens]

Originally Posted by MAG

Yes, Yes, and Yes. ????? If you install, bore out the intake\to match the B carb. to take advantage of the additional power.

Is there any reason to bore out the Model A manifold instead of running a Model B manifold?

Charlie Stephens

[Jim/GA]

Originally Posted by Charlie Stephens

Is there any reason to bore out the Model A manifold instead of running a Model B manifold?

Charlie Stephens

The Model B intake manifold has the carburetor installed at a slight angle, compared to a Model A intake manifold. If you use the B manifold, the choke rod on the A will not line up properly with the driver on the B carburetor.

A pair of modified carburetor mounting bolts are sold to allow you to twist the B carburetor when you install it on the B manifold so that the choke rod lines up.

Or you use the A manifold and bore it out to a slightly larger diameter on the main runner, up from the carb mounting flange. This matches the throttle bore of the Model B carb with the bore of the A manifold, for maximum horsepower at wide open throttle (does not really matter for partial throttle operation -- the throttle is a greater resistance than the small intake manifold runner).

.

[old31]

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Interesting stuff, thanks.

So Jim, are you saying for everyday driving, not racing, I really wont notice too much difference unless its floored?

My engine has a 6.1 Snyders head, larger intake valves, balanced crank, V8 clutch, lightend flywheel, touring cam, 4 speed syncro.

[Ernie Vitucci]

Good Afternoon...I have used a B Carburetor for a bit over 10 years on my 1931 Tudor with a 5.9 head and a B cam in the distributor. I has a bit more power coming off stop lights and it runs nice and doesn't have as much of a tendency to stall at a quick stop. The float is positioned sideways rather than front to back. It does let in more air and it has an extra 'Power Jet' that the A Carburetor does not have. Renner's Corner 734-428-8424. Dave has flow tested Jets for the B and they are adjusted for the use of an Air Cleaner if you choose to use one. Ernie in Arizona

[Jim/GA]

Originally Posted by old31

Interesting stuff, thanks.

So Jim, are you saying for everyday driving, not racing, I really wont notice too much difference unless its floored?

My engine has a 6.1 Snyders head, larger intake valves, balanced crank, V8 clutch, lightend flywheel, touring cam, 4 speed syncro.

With the head and valves and cam you have listed above, I think you will really like the added performance of the B carb with an enlarged A intake manifold, even of not racing. Your modifications help the engine breather better and the larger intake manifold and carb throttle bore will compliment them well.

.

[Ernie Vitucci]

Good afternoon...I have used a 'B' Carburetor on my 31 Tudor for better than 10 years. I really like it as it does produce a bit more power with more air and also an extra 'Power Jet' that the A carburetor does not have. Dave Renner at Renner's corner has flow tested jets, and the brass fittings to connect the Model A Gas Line to the Model B Carburetor. The gas line of the A goes in on the side and the gas line on the B goes in on the front. If you are going to use a B Intake Manifold, he also has the modified bolts to keep the B Carburetor lined up properly for your choke rod. I think you will like the B Carburetor...Ernie in Arizona

[Terry, NJ]

[/B]There are three main differences in the B carb. Since it was an evolution, these could be called improvements.
First, The float's direction of travel. The A carb float has a fore and aft movement while the B carb is mounted sideways. What this means is the B carb float is less likely to stall out in a sudden stop.
#Two The B carb has a power jet (And early form of accelerator pump) that gives a little more gas when needed. Don't ever try to unstick a stuck carb by twisting the two halves. It will damage the power tube
#three, The bore is 1.250. The Mod A bore is 1.125 and the throat is larger. This means that it will process more air than the A carb. The Mod A engine needs to breath. Those larger intake valves need more gas and air supplying the runners to make any difference.
To bore the A manifold, you need a Bridgeport or similar machine. One needs to pretty precisely locate the manifold vertically and the travel of the drill or your drill will go out the side of the manifold. You've got a four inch hole to drill and several things can go wrong and you don't have much margin. I also flycut /skim the carburetor gasket surface. When you're done drilling, it must be polished and this is the tedious part. It's never enough, or so it seems. Then there's the current argument about whether you want a high polish or finish or maybe one with small scratches/ridges that are supposed to break up the unvaporized microscopic globules of gasoline. Who actually knows? I've seen both.
Terry

[31a]

I use a B carb and manifold on one of my pickups and it improved the power more fun to drive Bob

[old31]

OK, thats it. B carb for me.

[Bob Bidonde]

If it is power and smooth running you desire, go with a downdraft Holley 94.

[Gene F]

Ernie, do you know the float level, or perhaps the fuel level with the engine ideling? I have the spped parts, including the big bore intake. My B carb feels like it is surging on the top end. The fuel line from the firewall to the carb was new, so it's not that. Drives me crazy. Thinking about putting my double venture Zenith back on.