"Single plenum" 8ba intake
 

So I was watching Mad Fabricators the other day. Bob was working with the new big 97s which have the carb barrels kind of notched in between the barrels. He opened up the intake in between the two barrel openings to match the carbs. He said in turn it would allow the cylinders that needed the fuel more to be able to get it as opposed to being restricted. That almost turns it into a single plenum opening. Anybody ever try this on a factory 8ba manifold? Seems like it should work but I'm not super familiar with how the 8ba works. I may pick up a spare manifold and get down to business

Re: "Single plenum" 8ba intake
 

In 34, Ford went with their newly designed over and under (dual plane) manifold and a Stromberg two barrel. This is was done to stop starving the end cylinders of fuel, by having each throat of the two barrel carb "only" supply fuel to one bank of cylinders.

Was Mad Fab working with a multi-carb manifold? If he was, then the notching may make sense, but if working with a single carb manifold, then that would be defeating what Ford was trying to accomplish.

Re: "Single plenum" 8ba intake
 

Always thought that each throat supplied two cylinders on one side and two on opposite bank?

Re: "Single plenum" 8ba intake
 

It was a multi carb manifold, yeah. So did Fords new design actually make it better or was it a case of it's done let's just leave it alone?

Re: "Single plenum" 8ba intake
 

In order to know the actual effects of such mods you need an oxygen sensor on each exhaust port to monitor A/F ratios through the RPM range of the engine. Otherwise it's a pure guess.

Re: "Single plenum" 8ba intake
 

If I am not mistaken the notches in the "barrels" were to clear the nozzles in the EE-1 base for the improved idle circuit. Ask Max Musgrove about this.

Re: "Single plenum" 8ba intake
 

I agree with 34PKUP, that dual plan manifolds supply fuel to both banks. However, in doing research on the flathead manifold, all I could find was that the manifold was called an "over and under" and each throat only supplied one bank of cylinders. That is what my research found and it does make sense. Of course, the info I found could be wrong.

Re: "Single plenum" 8ba intake
 

Each plenum feeds half the cylinders but it is not left bank vs right bank. A single plane manifold pushes the torque peak up in rpm a little, is my understanding.

Re: "Single plenum" 8ba intake
 

The firing order for a Ford flathead is 1-5-4-8-6-3-7-2. If you look a regular flathead manifold over, you will see that one side feeds cylinders 1, 4, 6 and 7, while the other side feeds cylinders 5, 8, 3, and 2. This just makes common sense. If you take into consideration the unique cylinder numbering convention for flathead Fords, you will see that the cylinders fire on alternate sides of the engine and alternate sides of the manifold.

Clever, those Ford engineers.

Re: "Single plenum" 8ba intake
 

Before getting carried away with hacking up the manifold, remember that the 1932 V8 was 65 HP and had a single plane manifold. With the dual plane manifold in 1934, HP went to 85. Backyard engineering sometimes (oftentimes?) ends up with a worse result.

Re: "Single plenum" 8ba intake
 

Flow pattern of an 8BA manifold.
https://www.fordbarn.com/forum/attac...0&d=1642997907

Re: "Single plenum" 8ba intake
 

Cutting the divided section below the carb is terrible for normal street driving just as adding an open spacer is.

Re: "Single plenum" 8ba intake
 

I rebuild both 94's and Rochester 2G's. I like to test them on my test engine. Instead of changing manifolds, I use a 3-bolt to 4-bolt adapter from Speedway. To get it to run right, I added a divider to the adapter.

Re: "Single plenum" 8ba intake
 

Denny, I'm a fan of Rochester 2G's, too, but have never tried one on a flathead. How do they perform on your test engine with your divided adapter vs. the 94's?

Re: "Single plenum" 8ba intake
 

Not answering for Denny here, as he is plenty qualified & capable on his own, but he runs a 2G on his '51 full time, and has always spoken positively about it's performance. I can speak first-hand to the fact that 2Gs are one of the simplest, yet most reliable 2 bbls out there, and quite a few flatheads are running them these days. In fact, the word must be out, 'cuz they're getting a little hard to find, especially affordably! DD
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