i once read a story about "siamesing"your intake-ports.
This was done on a EFI v8.

-why would this improve performance?
-Will it also do any good on a carbed v8? (quess not, but why?)

cya

They were probably referring to a TPI base. Since the TPI intake track is so
long, and only make power to 4500, you can pick up upper rpm/HP by
siamesing it. It then acts like a short runner (Victor jr.) and pulls better
up top.

I had to think about this for a while..

This along the same lines as cutting down a dual plane intakes divider so that at rpm, the engine can suck from a bigger plenum.

The old L-88 intake was done this way and the 830 carb. used with it was stagger-jetted to help mixture distribution issues.

The carb. is still sold by Holley if I remember right. pdq67

"Siamesing" refers to the 86-92 TPI induction system. It is a three part intake manifold. The base, the runners and the plenum. Siamesing was done to the runners of this system by cutting into the tubes and joining them together. This basically was to increase the available plenum volume of the 'filling' cylinder but to also balance the signal in the plenum. And as it was stated, it was to increase the the volume of air at higher RPM's.....a trick that TRACO Engineering first pioneered with sequential GM TPI systems.

And a little FYI. The length was to straighten the air before it was introduced into the cylinder head and to keep the velocity up. Just as a "Tunnel Ram" does. So it has more to do with things than just low speed power production.