Notching divider on RPM?

[77cruiser]

I have a RPM spread bore that I want to put on my 421. It has a Vic Jr. on it now. Wondering if I should notch the divider, how much & where?

[F-BIRD'88]

Leave the full divider in place and try out various spacer types for effect.

[F-BIRD'88]

Especially if yiu drive it more than race it.

[BOOT]

I'd think a smaller single plane would be nice on 421 but lots of details I don't know. Ordered a Holley 300-261 to try sometime myself for kinda street/strip SBC, might do quick video when/if it ever gets here.

Not a SBC but spreadbore RPM with a notch https://www.summitracing.com/parts/edl-7164 Looks like it's a bit biased to the rear.

edl-7164.jpg

[BOOT]

I always liked some of the other brands basically RPM style dual plane notches, smoother than the rough cut eddy.

[BOOT]

Also what cfm is the carb?

[77cruiser]

Leave the full divider in place and try out various spacer types for effect.

Could try that.

[F-BIRD'88]

Consider adding a plenum divider to the Vic Jr.
Can make it attached to a spacer for strength.
Try that and compare.

[54chevkiwi]

That 406 i had that eric done the top end on had an rpm intake, he cut down the divider like the one in that pic, and put a supersucker spacer on it with an opposing cut in it like the one in the manifold.. it ended up as a sqaure hole in the middle. He wouldnt have done that if it didnt do something.. that intake was ported as much as it could be without cutting it open..
The supersucker was one with the 4 seperate holes.. i think maybe 1.5”-2” i dont remember..
Was a square bore though..

[BOOT]

That 406 i had that eric done the top end on had an rpm intake, he cut down the divider like the one in that pic, and put a supersucker spacer on it with an opposing cut in it like the one in the manifold.. it ended up as a sqaure hole in the middle. He wouldnt have done that if it didnt do something.. that intake was ported as much as it could be without cutting it open..
The supersucker was one with the 4 seperate holes.. i think maybe 1”? Maybe 1.5” i dont remember..
Was a square bore though..

HVH ST4150-4AL got one of those myself

edit: Whoops put wrong part number forgot there was two, second is ST4150-2AL

[77cruiser]

Also what cfm is the carb?

Large primary Qjet. So 800?

[1980RS]

You mean like this?

[steve cowan]

On a 430-440 hp 383 sbc
Track testing I found super sucker spacer worked the best on airgap
People have to think about why the divider is milled down and think why Eric milled base of spacer as well.

[steve cowan]

I have a RPM spread bore that I want to put on my 421. It has a Vic Jr. on it now. Wondering if I should notch the divider, how much & where?

Jim,
Has vic jnr had porting/plenum work ??
If not and you do change to airgap it would be nice to rework the jnr when you change back later on.
The airgap will be nice at low speed but run out of puff on your cubes rather quickly in my opinion

[1980RS]

On a 430-440 hp 383 sbc
Track testing I found super sucker spacer worked the best on airgap
People have to think about why the divider is milled down and think why Eric milled base of spacer as well.

That spacer sure did not work on my BBC Air Gap last time I used it. The engine liked the 1" open spacer better.