I was just wondering if anybody has modified the RPM manifold plenum divider like we used to do to the LD340(as suggested by D.C.). I know from experience that it really worked on the LD340 and would think the same results would happen on the RPM. Anybody tried it. I know I would if given the chance. Wouldn't even be hard to put it back in if didn't.

I just got a RPM intake for my 440. it has a notch cast in the center divider.

is that the type of mod you are talking about?

I have a LD4B,it has a untouched divder down the middle.

what mod is done to the LD340?

only thing I have read was how they cut a notch in the rear of the divider for a 3 barrel holley carb so the rear butterfly would open(2 primary butterflys with one oblong butterfly on the 2ndary)

The Mod for the LD340 he is reffering to should be detailed in the MP engine manual if you have one and want to see how the divider is modified.

Humm.. I dont have that manual,i will look around and see if i can find it.

Mill the divider down until it's 3/8" tall and round everything off.

I'd find one that is already done and not mess up an original.

From the frt and rear throttle bores you measure back 1/4 inch and then mill straight down until 3/8 off floor of manifold and remove divider. Also you only round edge on right side (passenger) of frt and rear walls that remain. Rest is left sharpe or flat.

here is a shot of my RPM intake with a notch cast into it.

so you would mill it straight down till 3/8' of the floor to remove the divider wall.

i wonder if that is the idea behind the cast in notch on the rpm intake.

looked my LD4B over and it is divided down the middle with no notch.

so milling the divider down sort of makes a open plenum area but still has a duel plane floor in the intake.

very interesting.

one more shot.

To answer your question. Yes, but you need to remove more than how your divider is now, It starts down to late. 1/4 inch from top and bottom down from top of throttle bores. Here is my take on it. you will lose some very bottom end torgue and HP. very low Rpm's say from idle to 2500-3000 then pick up to 55000-6000 and then fall a little short to a single plane. In other words it is somewhere between a dual plane and a single plane. If you are some what traction impaired or Rpm limited it should help. Best of both worlds in daul plane single plane manifolds.

How much horsepower gain are we talking here? I've got a brand new SB RPM and about ready to finish assembly, could be a candidate for some mods.

An open spacer would do the same thing, or a 4 hole mashined the same way.

I can't tell if it's better but I can give you my combo and E.T. 360,Modified LD340 (divider cut down to 1/4" and rounded),224@.050" hyd roller,TTI headers w/2 1/2" full exhaust, 650 Holley D/P,2.02 int with hand ported mid 70s castings,9-1 (measured) old style TRW. In my Challenger with a stock 2.42 1st gear 4 speed ,4.30 ,9X29 it ran 12.52@110. 3750 w/ driver.
Doug

On my RPM I milled the divider completely out. The 340 I had it on ran low 7.60s (1/8) at 3400# with iron heads, hydraulic cam and pump 93.