I have noticed that the bottom surface of the factory dual quad manifolds sometimes has two large set screw type bolts while some manifolds have a completely smooth bottom surface. What is the significance of these differences? Pictured below is a two-bolt type.

 

Steve

The ’57 Ford dual quad intakes all have those threaded plugs in the bottom.  Those were to facilitate the casting process.  While many of the Ford produced aluminum intakes for their various engine families do have those plugs in the bottom, most of the aftermarket intakes do not employ them.  These just represent differences in how the manifolds are cast.

Lorena, Texas (South of Waco)

While Ted makes a good point,

I"m throughly convinced that each of those plugs adds 5 horsepower for a 10 horsepower total gain.

Its a deep Ford racing secret from way back so dont tell anyone.

Oldmics

Ted, thanks for the info. I'm still a bit confused though. I have a factory dual quad manifold (ECG 9424D) that does'nt have the casting plugs. The bottom surface is completely smooth. Were some made that way and others not?  Thanks again for your expert information!

Steve

Sorry Oldmics, I got to let out the secret. They would have a bottle of nitrous hidden under the car and plumbed up the back of the motor under the intake to those plugs very inconspicuosly, then it was actuated by the overdrive kickdown switch under the gas pedal. People thought they just had a normal overdrive.

Others  just used the plugs to drain the manifold if they had leaky power valves in their carbs.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Ted, i stand corrected. Went out to the garage yesterday and the smooth surface i thought existed on the ecg 9424 D wasn't smooth at all. It had been so long that i had looked at it. It has the two plugs just as you said they all had. My apologies for the erronious post.

Steve

Steve.  Thanks for the clarification on the plugs on that other manifold.  Sounds like you have two intakes?  If so, what are the dates on each of them?

 

Thanks to the information provided by Dennis K., it’s known that the ECG-D manifolds were cast at Schmeller Aluminum Foundry in Cleveland.  And it looks like there were around 5500 of these intakes cast.

 

This lead in brings up another topic which would be to identify the various casting dates for some of these manifolds.  Most of the ECG-D dual quad manifolds have the date on the top side behind the thermostat.  It would be interesting if everyone that has one or more of these intakes post their intake casting dates just to get an idea of the frequency that these intakes were being cast.

 

Here are some dates for ECG-D 2X4 manifolds to get this started:

12-14

1-22

3-29

6-5-57

Lorena, Texas (South of Waco)

To which I can add (notice now we have some consecutive dates for production of the manifolds)

10-15-56

12-5

12-13 (then Teds 12-14)

1-18

1-22 Teds

2-28

3-6 , 3-7 , 3-8  Theres a good run !

3-13

3-29 Teds

4-3

6-5-57 (Teds) -then 6-6-57

6-10

Bring em on

Oldmics

Mine is 1-22 with the "S" on the bottom.

Those plugs were to close up two holes which would have been used to support the heater core during the casting process. They would also have been helpful in removing the core sand after casting. Designers try to eliminate them, foundry guys put them back in to reduce scrap and core removal issues. Ted's got it right.

Frank/Rebop

Bristol, In ( by Elkhart)