Flathead 4 barrel intake port help please

[Kilohertz]

Hi guys,

I'm working my way through tuning the GM TBI fuel injection system on my '49 F-47 8BA and I am working on splitting the left/right injector drive and need to know what intake ports are fed by the left and right sides of the intake. I really don't want to remove the intake to confirm this, but based on pictures I have, I think it is as drawn below. Does anyone know if most, or all 4 barrel intakes would follow the same pattern or is it manufacturer specific? I know the left and right holes, i.e. bank 1 and bank 2, have a common plenum under each, separated by a divider. I have used a vintage Fenton intake.

Could someone please confirm if I have this correct?

Thank you.

Cheers

 

[38 coupe]

The front and back two on each side share the passages with the inner two from the opposite side. The carb flange holes are shared with the inner intake ports on their respective sides.
To clarify:
carb holes you have labeled 1,6 and 4,7 are for ports 1, 6, 7, 4
carb holes you have labeled 5,2 and 8,3 are for ports 5, 2, 3, 8

 

[petehoovie]

Hi guys,

I'm working my way through tuning the GM TBI fuel injection system on my '49 F-47 8BA and I am working on splitting the left/right injector drive and need to know what intake ports are fed by the left and right sides of the intake. I really don't want to remove the intake to confirm this, but based on pictures I have, I think it is as drawn below. Does anyone know if most, or all 4 barrel intakes would follow the same pattern or is it manufacturer specific? I know the left and right holes, i.e. bank 1 and bank 2, have a common plenum under each, separated by a divider. I have used a vintage Fenton intake.

Could someone please confirm if I have this correct?

Thank you.

Cheers

 

[51 MERC-CT]

The 4 bbl. carb. functions for 99.999% of the time as a 2 bbl. carb. using the primary carb ports.

 

[Kilohertz]

Thank you fellows, you have confirmed what I originally surmised based on the pictures I have. The tuning continues, I am making more progress everyday, engine running very smooth and very snappy throttle response.

Merry Christmas.

Cheers

 

[Ken Henry]

If it's dual plane, without a common plenum under the carb, I think it should operate like how 38 coupe described. The idea is that no two consecutive cylinders draw from the same side of the carburetor. I have my EFI setup like what 51 Merc-CT showed, since I have two one barrel throttle bodies spraying into a common plenum. It works OK but I found that I needed to fire both primary injectors four times per revolution or I get fuel starvation in some cylinders under high load/low RPM conditions. You'll be much better off using the dual plane. Ken


81E4F735-C76B-400B-B889-208BFE47883C by kenhenry_06268, on Flickr

 

[Ol' Ron]

I don't quite understand this solution. Considering the fact that the manifold acts like a 2bl when running in cruise feeding all 8 cylinders. Then when the secondary's open, they feed all 8 cylinders. Seems like the 4 carb ports feed into the same place, and then distributed to each cylinder. Might be old age.
Gramps

 

[Kilohertz]

Thanks Ken, yes the Fenton is a dual plane manifold and I am running Sync only fueling, which means each injector pulses once per distributor pulse, and they fire alternately meaning left bank/injector, then right bank/injector, then left bank and so on. I don't know how to confirm if the cylinder that is firing is on the side that is getting the fuel, but since it's running so well, I'm not going to try to figure it out.

Ol Ron, glad you showed up, I was wondering where you were. As you may have read, I have successfully installed a complete GM TBI setup from a '91 C1500, but using a throttle body from an S-10 2.8L as they have smaller 1 3/8" ports and flow a nice 285 CFM or so, I think. Works perfect on the C1BA flattie so far, not loaded yet, just running it in the shop. I have been tuning the ECM BIN file for over a week now and am on rev. 11 so far, gets better all the time.

Merry Christmas

Cheers

Video link

https://www.dropbox.com/s/7h501pl5cp9rfel/IMG_1481.MOV?dl=0

 

[Ken Henry]

Aren't there two 'volumes' in a dual plane manifold? So the left ports (either front only or front and back when you stomp on it) feed 2, 3, 5, and 8 and the right ports feed 1, 4, 6, and 7?

 

[Jack E/NJ]

Seems like you could stick your finger in a hole, curl it and see if your fingertip shows up in the other holes.

 

[tubman]

This is interesting. I have 4 different makes of flathead 4 BBL intakes (Fenton, Sharp, Edmunds, and Offenhauser). When I get back to Minnesota this spring, I'll have to check and see if they are all configured the same. At this time, I'll bet they are. I have always heard that Fenton made the best 4 BBL flathead manifold.

 

[38 coupe]

Not a topic of discussion on this thread yet, but that carb adapter plate had a big mismatch to the intake. Anyone have any experience on how much that hurts (or doesn't) engine operation? Looks to me like you would get restrictive turbulent flow right where you want the mixture to be changing direction into the plenum.

 

[51 MERC-CT]

Not a topic of discussion on this thread yet, but that carb adapter plate had a big mismatch to the intake. Anyone have any experience on how much that hurts (or doesn't) engine operation? Looks to me like you would get restrictive turbulent flow right where you want the mixture to be changing direction into the plenum.

Would be pure speculation as to whether any mismatch did or did not effect
performance.
But installing without taking note of any mismatch and correcting for optimum flow would not be prudent.
Also doubt if installed without doing so, one could document any difference.

 

[Kilohertz]

Aren't there two 'volumes' in a dual plane manifold? So the left ports (either front only or front and back when you stomp on it) feed 2, 3, 5, and 8 and the right ports feed 1, 4, 6, and 7?

ON both my Offy and Fenton, you can put your finger in the left side and see it in both front and rear holes, i.e. the left side is open front to back, but separate from the right side. Same goes on the right side, front and rear ports open into a common plenum.

Cheers

PS 38 Coupe, that adapter shown in the first post photo was for a large bore Holly or similar, first thing I did was remove it and machine and polish my own to fit correctly which is the reason I turned the throttle body 45* as the bores were within .080" match to the manifold this way and all I had to do was give the adapter plate a little tweak with the Dremel to sneak off the .040' on each port.

 

[Jack E/NJ]

I have an OT dual plane 4-holer for a carter on which I tried three wood spacer/adapter configurations shown below. No noticeable difference between them. I'd also expect not too much noticeable difference between a wide open adapter or the 2-hole/oblong adapter for squirters. Except perhaps more flexibility in how the carb or squirter is mounted.

 

[51 MERC-CT]

ON both my Offy and Fenton, you can put your finger in the left side and see it in both front and rear holes, i.e. the left side is open front to back, but separate from the right side. Same goes on the right side, front and rear ports open into a common plenum.

Cheers

Interesting in that I am running an Offy 4 bbl. with an Edelbrock carb. and never really checked the fuel distribution.
So is this the way the distribution is.?

 

[Kilohertz]

Yes, that's it. Your modification to my drawing makes it much clearer.

 

[Ol' Ron]

I'm looking for a 96 GM TBI system. I made an intake about 20 years ago, picked up Magnason computer and instructions somebody els put together (It didn't work). I now have a grand son that might be interested in makingit run. Be nice to have the engine harness as well
Gramps
PS don't these also work on a port injecton mode???

 

[Kilohertz]

Hi Ron,

There is a lot of good info on this link I started earlier this year...and I will be detailing my adventure in a new thread when I get a moment this Christmas break.

https://www.fordbarn.com/forum/showthread.php?t=294486

I would strongly suggest staying with a '87-91 TBI system, from either a car, van or truck. The ''94 and newer got way more complicated. The computer of choice would be 1227747 which were used in most trucks of that era and are relatively simple to program and very well documented. I can help you a lot as I have been working on this for a few months now.

Cheers

 

[38 coupe]

Interesting in that I am running an Offy 4 bbl. with an Edelbrock carb. and never really checked the fuel distribution.
So is this the way the distribution is.?

The drawing indicates a divider between the front and back of the manifold, which is not accurate. The green and yellow lines are all one passage. The red and blue lines are all one passage. Since only one cylinder at a time is drawing on any one passage both barrels in each passage feed all cylinders in that passage.