B G Racing, that was a kick ass answer. I can only add for younger/newer members to the
Mopar world that MP has said to use this mod with cam lift of greater than .550. Which you have to understand that this is a read between the lines statement and you will have to remember that most of the cams back in the day when this was written were pretty big on duration at these lifts. AKA, Do this mod with a big ass cam only.
The mod was a "cheat mod" for the dual plane rule in the middle car program. As I was told. I can see it. It's still a dual plane!
I did this to my old LD-340. It helped the top end significantly! Mid range as well. I ran a cam as small as 216@.050 intake duration and it was still OK. Though it shined really well with a big cam.
