LD4B or LD340
The LD 340 was basically the factory early 340 intake only in aluminum I have one on my fresh rebuilt 340 running factory exhaust manifolds. Ive been told that the new elelbrock air gap is the one you want especially with headers. Not sure about the LD4B. Correct me if Im wrong.
The LD-340 is a high rise dual plane intake designed for the 340 - 360 and larger engines. It is not for a 318 unless it is really pumped up. And that is debateable. It is not a simple or basic rework of the factory iron intake.
It is taller with easier, nicer & larger flowing runners.
The Edel. RPM and Air-Gap version have the same performance showings and only differ down the road when the engine has been running for a while. The runners stay cooler when in operation on the air gap vs the RPM which has the heat passage. The heat passage in the RPM makes it an excellent dual purpose intake for all seasons.
LD-349 vs RPM. According to those whom have tested them both, theres no real difference between them and say not to bother with a swap to the RPM. No meaningful power was found between them, according to them.
(I'd love to waste the money myself and find out.)
Some have claimed they called up Edelbrock and spoke with tech which told them, Dont bother with a change.
On the LD4B, what C130 Chief said. I also run one on my 318.
Somewhere in this place I posted pictures with measurements hieghts of the intakes;
Stock 4bbl, LD4B, LD-340, RPM Air-Gap.