I've been disassembling my 71' roadrunner to get it ready for restoration. Right now I'm trying to figure out what a good cam would be for my motor. The car is completely stock. My intention is to have a good street machine that can dip into 12.5 to 13 et at the track. I've been told the MP484 lift grind would be good but the MP474 lift would be better because I intend on keeping the factory AC. Is anyone using these cams or have suggestions for something better.

The plan so far is to keep the motor factory looking but replace the internals to create a sleeper. I'm going to port and polish the 346 heads, put on an edelbrock performer intake, and am debating on putting on a T-quad or keeping the 750 competition carb already on it (previous owner). I took off the nameplate of the carb in order to make it look like a factory AVS carb. With the exhaust, I'm going to open up the factory hi-po manifolds and probably run a 3in. exhaust to help compensate for the manifolds.

The rear end has a 3.23 sure grip posi and the car is a factory 4 speed. Another question I have is if a 69' roadrunner 4 speed better than a 71' 4 speed. The previous owner gave me the 69' 4 speed as part of the deal.

If anyone has suggestions as far as the cam, carb, intake, or anything else I'd really appreciate it.

PS I don't want to build a stroker motor

i've heard of a few people running the 484 cam in 383s, but none with AC...if you're sticking with MP parts, the MP online catalog has a chart showing which items to choose to get your car into a time frame - idk how accurate it is, though. maybe look into a different, more modern cam grind - i think people keeping manifolds get a custom cam to make the most of it. being a 4 speed you won't have to worry about a converter (wish i was in that boat ), maybe look into a 3.55 rear. i'm sure there's someone that's done what you plan on doing that will chime in

The 4120235 484 cam is pretty big to be tossing in a 383 with A/C and 3.23 gears IMO..??

I wouldn't think so because its only two or three steps up from the factory cam that's a .450 lift. I'm sure the lobe sep. on the MP 484 is a little more radical than the factory 115. That's what I'm trying to figure out here though because I have no experience with a 4 speed. Always worked with automatics and torque converters. I figured with the 4 speed putting all the power to the rear, the 3.23 sure grip would hold up fine. I spoke to a guy with a 71' charger and he said the big problem with this body style is traction in the back. So if I bumped up the gear to a 3.55, would it be that big of a gain? That should be the same as swapping a 3.42 to a 3.73 in my malibu. There just isn't too much of a difference is there?

And I haven't a clue either how the AC plays that much of a factor in the performance, but supposedly it does. Another question I'm throwing out here is is there a way to convert that massive factory AC pump from R12 to R134 or am I going to have to replace the entire system including the pump?

3.23 to 3.55 isn't a big jump, just something i was throwing out there if you wanted some more acceleration and to help out with that cam - maybe go to 3.73 (?) if you wanted to step up acceleration even more. the a/c compressor will create more drag - maybe that's why you were advised to stray from the 484. the 484 seems like a pretty radical cam for a 383...kind of like throwing a 509 in a mild, factory spec 440...not going to perform that well, unless you rebuild and bump up the compression a bit.

PS. '71-2 Plymouth = best looking

I want to get the compression up to 9 to 9.5:1 on the motor, which should definately help. The big thing that I'm trying to figure out is what grind cam would work well with the AC pump? I'm not worried about vacuum because I have manual brakes, with power steering. BTW all this stuff is bone stock. I'm just curious how dependable the purple shaft grinds are because guys claim new technology has created better cams such as the comp cams xtreme energy line and that the MP cams are a 30+ year old design.

that's a bit higher than stock, so maybe you'll be okay with a 484 cam. i'm going to use the Comp XE 268 in the 440 for my '71 (also manual brakes, PS). it's a .477/.480 lift cam good to 5800 RPMs. i would think that cam, or maybe one step above it would work pretty well in a 383 4 speed ( i have an auto, so without changing converters, i'm just about limited to the 268). i was really hoping someone with a 383 would chime in....

Been there, done that. Too much duration & overlap, not enough lift. Put one in a .030 over balanced/printed 383 RR, 3.23s & stock converter. Sounded wicked, but was soft on the bottom and not well-mannered even at 4* advanced. Lots of fun over 3000RPM or so. Terrible gas mileage. I've since been very happy with Engle's stuff, which takes advantage of the Chrysler lifter size. Especially with AC, I'd go somewhere around their 214/224 @ .050, .470/.504 lift split-pattern hydraulic. Had that spec cam in a 406" Duster with AC; good vauum, throttle response & manners, sounds healthy, 17MPG at 70, happy with a 3.21 gear and stock converter. The MP 284/484 is old tech; still popular, but better stuff is available.

I understand that the MP grinds are old tech but its proven technology that works. My dad is running what I think is the comp cam XE268, it is a .540 lift cam with 280 duration in his 67' Dart GTS that has a built 440.

Topside, were you talking about the 484 grind not having enough lift and too much duration and overlap?

Run a modern cam.

I ran the MP .484 cam in a 383 Dart and it ran great but it was set up for it. It was a basically a stock 383 with the heads shaved for 9.5 comp and a mild bowl blend job. I had the Performer RPM intake witha 750 DP. I used 3.91 gears and a Turbo Action 10" tight 3000 converter. I loved the idle and the car ran a best of 12.31 @ 110. But I have to agree with everyone that it's not the best choice for your combo. It likes some gear and comp to keep some low end in it. I would want to use at least 3.91's in a Runner with the .484 cam and I would advance the cam to about a 104 centerline. Ron.

Alright after doing a lot of research I've decided that the .484 MP cam is really the biggest that should be put in a 383. I'm thinking the .474 grind MP cam is a good choice with my 4 speed and 3.23 gearing. It should also work with my factory AC, even if I have to swap out the factory pump for an R134 pump. I will also shave the heads and port'em to get better flow and CR. IMO, from what I've been reading, my 346 open chamber heads can perform just as good as a closed chamber head once they're built right.

I vote for the newer Comp grinds like the retro 509 grind.If you open the ports up with the templates that 509 will really wake that 383 up
Gus

I've built 2 383s.. 9.8:1, stock heads and vavle gear, one dual plane one single, both with 750 3310 Holleys. I used the XE268 in them. Thye idle at 700rpm, pull from idle to 6K, and have no issues. I dont think any MP cam is the way to go for this one. Get something design in this millenium and that is made without the usual production issues. If you do run an MP, then make sure they degree it because it's going to be off.

From what I understand, when running factory exhaust manifolds, you’re better off with a 112-to-114 centerline.

Also, as already mentioned in this thread, go with a custom cam for your application.

In my 383, I’m going with a Mr. SixPack custom grind from Engle Racing Cams which is designed by Bob Karakashian. The cost is a bit more than an off the shelf cam but worth it. $235.00 to your doorstep and that dose not include lifters.

But that cam has bone stock 440-6s running in the high 11s on factory polyglass tires. You might be able to get the ETs you’re after with you're 383.

You can give Mr. Karakashian a call and he’ll talk it over with you.



Mr.6Pack Racing Engines - link

i ran a P.A.W. cam in my 85 short bed pick up back in the early nineties,went pretty good for the price.had a rumpity idle and good power.the 383(66) went 13.1's with a 650 holley and a od 4sp and 3:55's,tube headers.

Performance Hyd Camshaft
Duration @ 0.050 Lift: Int. 224° /Exh. 234°
Advertised Duration: Int. 290° /Exh. 300°
Gross Valve Lift: .465"/.488"
Deg. Lobe Center: 112 LC

Recommended Lifter Part#: PAW- 2011 Qty. 16
NOTE: 1958-67 use PAW-812 Lifters
Recommended Valve Spring Part#: PAW-VS320 Qty.16

"
Item# PAW-22988

There are (2) 284 Mopar hyd cams 1 bolt for the big block.
The original P4120235 and later P50078975, the later one has more overlap (114 degrees vs. 108) and is better for the street. The original needs at least a 3.54 rear end.

Just my $0.025..

Like others are saying, go with a modern grind.
You going to need as much cam/compression/gear as possible to get to 12.5-13.0.
I doubt you can do it with a 383/3.23/old school MP cam/Factory manifolds.
Then again the F.A.S.T. boys could probably easily make that combo reach its goal....

Well from doing all this research, the MP 280 grind seems to be the best all around cam for driveability with the four speed and AC while still putting out plenty of torque, plus its a good hemi grind as well. Been reading up a lot of specs out of my dad's Mopar Performance Shelby's Secrets book that was published in the mid to late 80's. It looks like the mopar bible lol.

With the exhaust, I plan on opening up the factory hi-po manifolds and running a 3 inch flowmaster exhaust to help those manifolds out. The factory 2 1/4 exhaust pipes and mufflers are still on the car and are in good condition with minimal surface rust, but I have a feeling they won't allow as much flow as a 3 inch flowmaster exhaust (duh).

One investment I'm looking at is 440source's new stealth heads. I can easily paint them and they'll resemble the factory heads and help lighten up the front end to compensate for the heavy AC pump. Plus they're a better design than the 346 heads I have. If budget doesn't allow that, then I'll rebuild the 346 heads to a point where they'll perform to the best a factory head can.

For intakes, i'm kinda stuck. I'm trying to choose between eddy's performer intake, RPM performer, or the M1 dual plane intake. Remember that I'm trying to keep the motor and car looking stock while replacing all internals that no one can see, and making a lot of torque low while have hp to closely match the torque. So I was thinking the performer closely resembles the factory intake, but the RPM performer seems to be putting out higher numbers. I dont have a clue on the performance of the M1 dual plane intake. Anyone have input on these intakes?

With the carb, I'm going to be using a Carter Competition 750 cfm carb. I removed its nameplate and it resembles the factory mopar AFB carb. After a good rebuild and a little jet work and it should work great.

Finally, I'm really considering rebuilding the rear end with a 3.55 gear since I do plan on using a somewhat tall tire and it will give better response etc etc.