Just an update and to close this one out.

I got my newly modified intake manifold from the machine shop.


I also picked up my heads (now with positive type seals) and flywheel.



As always, thanks to everyone for the advice, always appreciated.




Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

Yes.

Lorena, Texas (South of Waco)

do you all think I would get any performance improvement doing this when running a smaller CFM 1272 or 1273 carb?

Great info here, I think I'll try milling out the two slots. Thanks for the info.

I assume you have a manual trans?  going too big on the spacer can bugger up the linkages. From memory I just put a 4 hole 1" spacer straight on  [modified for PCV] mines an Auto.  



"Came too close to dying to stop living now!"

Nice one, thanks. I have ordered a 2inch 4hole spacer and will get the manifold machined.
Thanks Everyone for the advice, much appreciated!


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

The spacer should be 4 hole or divided (2 ovals) in order to maintain the dual plane functionality.

Here are some examples.  The one in the middle is a hybrid of the two, two ovals on bottom, 4 hole on top.





Lawrenceville, GA

I realize it already a dual plane manifold.
Ok so I just want to clarify, please correct me if I’m wrong- machine the 2 slots in the manifold but use a 4 hole spacer to retain the low end torque, correct?


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.

The manifold is already dual plane.  Modifying it as Ted shows makes it work better and accommodate larger, modern carbs while maintaining dual plane functionality.

You can machine it flat.  Others have used epoxy to fill in the valley in order to make it flat.  The holes should be opened up to match the carburetor, at the very least.


Lawrenceville, GA

Thanks Ted and Joe.
In this instance I’ll go for the 4 bbl spacer, but hypothetically if I were to go for the dual plane modification on the manifold, would I machine the surface flat an open the holes up slightly?


Thanks, Dennis.

56 F100 - 272 Y Block
NSW, Australia.