Been a looooong time. I'm about to tear into my Plymouth again. It's been garaged the last few of years due to a wicked shimmy in the rear. Figured out finally it was bad pinion angle... or more accurately, zero pinion angle. My rear springs flattened out completely.

Anyway, I'm redoing the rear suspension. While I do that, I'm swapping out my 3:90's for 4:56's. I want to swap out to a single plane intake. But I've been out of the game for so long, Mopar discontinued the M1 intake

So, what do you guys suggest? Block is a .060 over 383. Heads are 456's, ported... but I'd have to dig up my flow sheets to tell you what they flow. I'm running a .528 Mopar cam & a Holly 830DP Mechanical. An Edelbrock Performer RPM is currently installed w/ an Edelbrock Performer RPM nitrous kit.

Any suggestions would be awesome!

Josh

With the 4.56's I would guess the new Trick Flow 383 single plane would fit the bill, if it'll fit under the hood. Some might suggest you stick with the RPM. And yes, bummer about the M1. I would like to have one.

I would try the RPM first with the new mods and then decide if you want to change the intake or not
If yo decide to get rid of the RPM I have a new motor with a Mopar M1 4150 intake on it that I would be willing to swap for your RPM if you pay the shipping for both I had this motor(400 block with a 440 crank and rods, 451 C.I ) on a DTS engine dyno with a Holley HP 950 carb and it made 489 HP on CA pump swill in Ontario, CA on the Carb Shops DTS engine dyno with that intake
PM me on here if that is something you want to do

I'm just thinking that with the 4.56's, it'll run out of the RPM's power band really quick. I'll see how it goes. Cab_Burge... PM inbound.

Thanks guys!

Are you going to use the nitrous?, if so you may want to keep the 3.91,s How heavy a car and what diameter tire and ET have you run.

I'm thinking, you probably want to Stay with the b rpm, regard less. Don't have enough info from you for any gear change.

Check and fix your pinion angle, wrong angles don't cause a shimmy though, More like a vibration, Shimmy, no.