B carb on A manifold .

john charlton

john charlton

Well-known member
I know it is said the B carb gives just under 4 BHP extra . This is on a dyno with wide throttle openings the kind of driving us sedentary old geezers would not do . As in a previous post Henry never bored out an inlet manifold to match carb to manifold throat dimensions . The KAYCE carb which is the same as a Zenith 1 was factory fitted to the narrow bore AF inlet manifold this gives a 1/8" step in the inlet tract Ford engineers were quite happy with that the AF car runs just fine . The thinking must be the throttle plate gives more obstruction . Pics to follow so you can see clearly the factory mismatch . This is double the mismatch in the English AA truck application where Henry put a B carb on an A manifold .

John cloudy warm summer evening Suffolk County England .
 
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Hey you old phart :-), who are you calling a sedentary old geezer? I'm 85 and going to run my banger at Bonneville in August, aim to better my best time of 167.450.
 
But Jim you are a Legend !!! I am only 83 and am for sure a sedentary old geezer as I suspect a lot on The Barn are too !!! . ( no disrespect of course )

John in same place same weather .
 
John,
I'm 85 and I know for a fact Jim is 1 month younger than me.That "whipper snapper" deserves all the disrespect we can give him. We all qualify for the old farts club. but we are younger than our cars.

I run a B carb on an A manifold without boring it bigger. There is a good seat of the pants improvement.

Richard
Anaheim CA
 
Yeah, you can do all that! I mean run B carbs on unbored A manifolds. It will sort of work. But, when you think about the actual reasons for cleaning up a manifold (Model A or otherwise) You realize it requires more than a hole connection from the top of the carb to the block. Think about the actual function! Moving the air gas mix to the cylinder from the carb, and as quickly as possible. This results in increased volumetric efficiency or as a mechanic might say " You get more gas in the cylinder to make a bigger explosion!" Look up "Porting and Polishing" on youtube. There are people claiming as much as a 15 HP increase by P&P on modern engines. The whole idea id to prevent choke points and turbulence. Both create turbulence and slow down the passage of fuel/air to the cylinder.
Terry
 
I have a B manifold because I am afraid to have mine (A intake) bored on a vertical mill because it might weaken it. If the thing busts on the highway I'd be on a tow truck. You know, seems like every time I try to hire some work out it's; A) not as promised - time, materials used, etc, B) costs about 3 times what I think it should have, C) I have to do it again, or do it again myself.
 
I am running a modern universal Zenith model for the A right now on my car. The carb to manifold bores are just the opposite but it runs real well.
 
Gene F said:
I have a B manifold because I am afraid to have mine (A intake) bored on a vertical mill because it might weaken it. If the thing busts on the highway I'd be on a tow truck. You know, seems like every time I try to hire some work out it's; A) not as promised - time, materials used, etc, B) costs about 3 times what I think it should have, C) I have to do it again, or do it again myself.
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You are correct to be careful! This why I use a pin to locate it. The pin will run from top to bottom of the runner and my drill does not break out of the side of the runner. You are also correct about the walls of the runner being very thin after drilling. Yet, I've never had one break or a drill come out the side. The pin I use is an old sector shaft that I cut the two teeth off of. The drill is an old carbide masonry drill. It mikes about 1.280. That could be lowered down to1.250.
Terry
 
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Terry said:
You are correct to be careful! This why I use a pin to locate it. The pin will run from top to bottom of the runner and my drill does not break out of the side of the runner. You are also correct about the walls of the runner being very thin after drilling. Yet, I've never had one break or a drill come out the side. The pin I use is an old sector shaft that I cut the two teeth off of. The drill is an old carbide masonry drill. It mikes about 1.280. That could be lowered down to1.250.
Terry
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Yep, the runner is not 90 deg. to the flange.
 
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