383 or 440 (Roadrunner)

Status
Not open for further replies.
Well, the AFB is not a bad design, but the Q-Jet and AVS have some advantages over it. The advantages are mainly in the ability to tune the secondary air valve opening rate and in how the part throttle operation's fuel curve is adjusted. More finite adjustment is available in the AVS and Q-Jet than the AFB because the AFB's air valve works odd of counterweights while the other two use spring tension with the ability to adjust it. Yes they are harder to tune, but properly set up they are lower maintenance. Any of the three is better than the traditional Holley in my book. Holley's part throttle circuit is way too limited in adjustability for my taste, and I have never had one that would stay in tune.

I have had Quadrajets, Holleys and Edelbrock AFB's on my cars at one time or another, and my preference is the Quadrajet and then the AFB. I have never had an AVS, so I can't speak about them from anything more than what I have read.

The Thermoquad is not a bad idea, it's just that the phenolic resin main body causes a lot of headaches because of it's tendency to warp over time. If you can keep that from happening, it's not a bad carb. However, that is it's Achilles' Heel, and a pretty big one at that.
 
Being a Chrysler Guy my whole life I happen to know a little something about them. In fact I have 2 440's (ones a 69 magnum) a 400 magnum (70 charger) about 6 383's (2 magnums) and a handful of small blocks laying around (unfortunately no 340 though 😢 ). If your planing on keeping it and driving it I'd go 440 (rb) all the way. You just can't touch them out of the box. Increadable motors. Theres alot of ways to build a 383/400 (b). There's even a way to make a stroker out of them using BBC rods and I believe even crank. I'd have to do some looking though my old mopar mags for the article but it was a budget stroker build. Either way you can't go wrong but it ain't any different to build and bolt in the 440 and the extra horsepower your gonna gain will make you happy you did. Just don't get rid of the numbers matching 383 and when you go to sell your car it'll still be worth just as much as long as you still have it to go with it. As far as carbs here's an ad for ya http://www.carburetor.ca/carbs/tech/Car ... index.html The afb and avs were pretty much the same carb with very minor differences (the AFB used a velocity valve, which is a counterweighted flap below the secondary venturi, the AVS used an air valve, which is a spring loaded flap above the venturi). Most parts actually interchange ( I have many of both laying around). The thermoquad came out later and wasn't a bad carb either (except for the warpage problem) but a spreadbore rather then a square. However the thermoquad like the Q Jet went through many changes year after year in terms of size and electronics and they were usually overkill for alot of the motors they put them on (mostly small blocks through the late 70's early 80's). The AVS was only used on one year of Chevy, usually a mopar carb while the AFB was used on pretty much everything at on time or another. The Thremoquads was a Chrysler and IHC carb but a few Fords and Lincolns got them as well. As far as carbs here's a few ad's for ya
http://www.carburetor.ca/carbs/tech/Car ... index.html
http://www.carburetion.com/Carter4.htm
http://www.thermoquads.com/
http://www.carburetor.ca/carbs/tech/Car ... index.html
 
I would go with a 440 and keep the 383 laying around if you have the room. That's almost like going from an SBC 283 to a 350... similar displacement difference (10ci more on the SBC).
 
Here's a pretty good site I found listing factory Mopar Engine specs, pretty good I thought. A well built 440 is a beast to say the least. Nice solid torque monster right out of the box. Find any mid(66)/late 60's Chrysler New Yorker, 300 or Imperial and you just hit a home run. However many other Mopar products had these same motors as options these had um standard. Although as I said I'm a mopar guy as well so don't just scrap the remains. Post them, someone will usually snatch it up quick. I personally love the old 300's especially 68 and I'd give anything to find a solid affordable one again (I had 2, 4 doors 😢 😢 )

http://www.mymopar.com/enginespecs.htm

here's a pic of the car I'd give up my monte for wouldn't even need a drivetrain in it....
5624350005_large.jpg


and a youtube of a stock one doing a burn out, just remember how heavy these cars were, this appears to be a completely stock one, 440TNT I believe 375 hp
http://www.youtube.com/watch?v=3ORjMJ-a9hQ
 
Ok I have to admit I have a sickness. I like to build hard running but reliable go anywhere streetable drivers. I would have to keep the #s matching for if you choose to sell her down the road. As for the build Edelbrock has excellent heads which should still be cleaned up along with a low 230s at 50 duration cam and a stroker crank to turn that 440 into a 500. Anyway just think about what YOU want and will enjoy the most.
 
the 383 is fine.

if motor is stock, you already have 906 heads. i'd up the comp ratio to 9.5 to 1, gasket port the heads and exh man and put it in a 484 cam.
either headers or even keep the orig HP manifolds.
throw in a set of 3.55's and call it a day.
 
Well I just found out from the guy over on moparts that I dont have the 906 heads. Cast numbers on my heads are 3462346. What I'm not understanding is if my motor is the HP 383 and has the 440 valvetrain, cam, and heads then why wouldn't it have the 906 heads?
 
patmckinneyracing said:
Well I just found out from the guy over on moparts that I dont have the 906 heads. Cast numbers on my heads are 3462346. What I'm not understanding is if my motor is the HP 383 and has the 440 valvetrain, cam, and heads then why wouldn't it have the 906 heads?

Because it's had 38 years since it rolled off the assembly line for people to mess with it...
The 383 was taking it's final bow in '71, making way for the more smog friendly 400, which is essentially a 383 with an increased bore. Transition periods make for a good reciepe of mismatching parts...even at the factory.
 
x2 on what Blake says, years bring many opportunitys for people to mess up a good thing 😢 But I'm interested in what you decide to do. Keep us posted.
 
Status
Not open for further replies.

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot UMI Performance

Contact Admin@GBodyForum.com for info on becoming a sponsor