Quote:

wrong...different plenum volume. different runners.

you will see a gain over the stock manifold with a performer.

the ld340 is a good intake.



In reference to replacing a stock 340 manifold with a Performer, that's a step backwards. The only benefit a performer has is weight reduction. Performer is a manifold designed for the 318 and smaller late model 360 runners. It's called a Performer 318/360 for a reason. The stock cast iron 340 square bore AVS or TQ manifolds are superior to a performer.

A Performer RPM or Air Gap is a whole different animal. Similar to an LD340 in characteristics.

Some LD340's have a Chrysler number cast in it, so an over the counter OEM maybe... The LD340 is one of the best manifolds ever for a SB mopar.

The OP asked about fuel economy. The performer or sp2p is a better choice in keeping velocity up than a LD4B.