would an A carb on a B manifold have less power than A on A?

[philosofriend]

Would an A carb on a B manifold have less power than an A carb on an A manifold?

I have to take my old manifold off and I'm thinking about getting a B carb. I want to put it back together (with a new Burtz block) but I won't have a B carb for a while. Seems like I might as well use Snyders manifold that is bored out for a B carb now and save having to change the manifold later.

The B manifold won't make the A carb run rough or anything, will it?

[BRENT in 10-uh-C]

Originally Posted by philosofriend

Would an A carb on a B manifold have less power than an A carb on an A manifold?

I have to take my old manifold off and I'm thinking about getting a B carb. I want to put it back together (with a new Burtz block) but I won't have a B carb for a while. Seems like I might as well use Snyders manifold that is bored out for a B carb now and save having to change the manifold later.

The B manifold won't make the A carb run rough or anything, will it?

Yes, it could but not enough for you to notice by the seat of your pants. The reason would be where the transition at the flanges is about a 0.120" per side that would momentarily cause a low pressure area which could cause the fuel to fall out of suspension. Again, you likely will never notice unless the engine was being run on a dyno.

The one thing you likely won't like about using a 'B' manifold is the carburetor will not sit at the same angle as what it did on the 'A' manifold. This affects connecting the choke rod. Elongating the carburetor mounting holes in the flange will let you twist it somewhat but it is not a 100% fix.

[Synchro909]

Originally Posted by BRENT in 10-uh-C

Yes, it could but not enough for you to notice by the seat of your pants. The reason would be where the transition at the flanges is about a 0.120" per side that would momentarily cause a low pressure area which could cause the fuel to fall out of suspension. Again, you likely will never notice unless the engine was being run on a dyno.

The one thing you likely won't like about using a 'B' manifold is the carburetor will not sit at the same angle as what it did on the 'A' manifold. This affects connecting the choke rod. Elongating the carburetor mounting holes in the flange will let you twist it somewhat but it is not a 100% fix.

When I fitted a B carburettor on my Ute, I bought a small universal joint made for 1/4 (from memory) inch shaft (the choke rod). I installed it in the rod just on the inside of the firewall so that the angle was pretty darned close when it reached the carby. It has worked well like that for years.
PS Doing any of this sort of work is more complicated on a RHD car because he steering box is right beside the carby.

[Y-Blockhead]

Originally Posted by BRENT in 10-uh-C

The one thing you likely won't like about using a 'B' manifold is the carburetor will not sit at the same angle as what it did on the 'A' manifold. This affects connecting the choke rod. Elongating the carburetor mounting holes in the flange will let you twist it somewhat but it is not a 100% fix.

Renner's Corner has a kit that allows you to align the choke rod. https://rennerscorner.com/carburetor.html I have never used it tho.

[Benson]

1. About the Renner's kit: In the early 1960s we turned down the bolts to realign both A and B carburetors when used on B manifolds.

2. The manifold from Snyder's mentioned in post #1 does not have this alignment problem because Snyder's takes a repro Model A manifold and bores it out to B size.

I have used this bored out manifold on my B block since they started to make this part and recently installed it on the Burtz engine.

I did not notice any performance difference when using the larger manifold. but the B carb does run better on either the A or B manifold.

[Bruce of MN]

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Manifold reaming from Barner Dave Gerold:

http://www.durableperformance.net/In...nt_7.20.17.pdf

[nkaminar]

The original poster talked about using a Model A manifold that was bored out for a Model B carburetor. In that case I don't see any issues with hooking up the controls. Aside from the dead flow area that Brent talked about, the bored out manifold should allow better breathing and thus performance, especially at higher rpm.

[37 Coupe]

Is the Zenith choke lever on the carburetor the same A and B? They look exactly alike to me but both A and B prefixes are used in some parts I have seen. Bottom line I need a B choke lever and only places I have seen repro are Model A and they only show 1928-1931. Sometimes if it fits B vendors show 1928-1934 4 cylinder.

[philosofriend]

I did not notice any performance difference when using the larger manifold. but the B carb does run better on either the A or B manifold.[/QUOTE]

In other words, you used a B carb on the same engine with both the A and the B manifold, and the manifold didn't seem to make much difference?

[Benson]

Originally Posted by philosofriend

I did not notice any performance difference when using the larger manifold. but the B carb does run better on either the A or B manifold.

In other words, you used a B carb on the same engine with both the A and the B manifold, and the manifold didn't seem to make much difference?[/QUOTE]B]



True, I could not feel any difference but I did not put it on a dyno to see if the dyno could measure any difference.
[/B]


[B]The manifold by itself may make a difference but I suspect it is too small to be noticed.

The 10 horsepower increase with the B engine has more to do with the 4.2 to 4.6 compression increase, the B carb and the better breathing camshaft.

The Model B head is the "One with the large C". 4.6 to 1.


Additional info:

Of all the things that I have tried to get more performance the thing which made the most difference by far was when I installed the 5.2 to 1 Police head (The head with the large B ) in 1963.

The difference is very noticeable -- more power and more torque when climbing hills.

1963 was many years before all of the higher compression heads appeared in such large numbers as today.

[Benson]

Originally Posted by 37 Coupe

Is the Zenith choke lever on the carburetor the same A and B? They look exactly alike to me but both A and B prefixes are used in some parts I have seen. Bottom line I need a B choke lever and only places I have seen repro are Model A and they only show 1928-1931. Sometimes if it fits B vendors show 1928-1934 4 cylinder.

Yes choke lever is the same

[37 Coupe]

Originally Posted by Benson

Yes choke lever is the same

Thank You Benson.

[philosofriend]

Thanks, that is helpful!

When I switched from an A head to a model B 28 years ago it gave a satisfying increase in torque at all speeds. Now I'm building a Burtz with the Burtz cam, a Snyder 5.5 head, and thanks to your information I will probably eventually put a B carb on my A manifold.

First I will get the Burtz running with my dependable A carb. One less issue to sort out with the new motor.

[Y-Blockhead]

Originally Posted by 37 Coupe

Is the Zenith choke lever on the carburetor the same A and B? They look exactly alike to me but both A and B prefixes are used in some parts I have seen. Bottom line I need a B choke lever and only places I have seen repro are Model A and they only show 1928-1931. Sometimes if it fits B vendors show 1928-1934 4 cylinder.

David at Renner's Corner https://rennerscorner.com/index.html has used parts in addition to new replacement parts.

[nkaminar]

The A carburetor restricts air flow. The B is a little better. To really get good flow to the engine a downdraft carburetor with two throats, like the Weber is needed. However you will not notice the difference at lower rpm where there is not a lot of air flow anyway, up to about 1,500 rpm. The higher compression head will help a lot with the torque but the higher flow Weber carburetor and manifold will make a big difference beyond 1,500 rpm.