BUSTN

I was told that porting the top part of the RB intake from a 12a will make more power,Is this true?My intake now has the four holes and they said making it one big opening will help me out???How true is this???Thanks

jayroc

What kind of intake? IDA I guess? I would say no. Unless someone has done it and tested the before and after on a flow bench.
Some people port the lower part that goes to the engine to port match the engine to the manifold, but this will decrease flow.. At least, on a stock manifold.

Sanspistons

I'm with jayroc; is it a RB 4 barrel manifold? If so don't bother porting, use a open spacer instead, easily obtainable and also easily reversable in case it doesn't work.
I'm using a 2" phenolic 4-holer with the secondary's blended together at the moment. Seems to work well.

Sanspistons; Rotor-Blessed, Rotor-Obsessed

Alak

iTrader: (9)

Ya use a 1" open spacer. But if you have a carburetor choice, go with a mechanical secondary carb. Edelbrocks are AWESOME.