I've been looking at changing the old AFB carb on my car to a Edelbrock 750. The AFB just isn't performing like I would like. My question, is the 750 too big for a 383? It's a factory 4 barrel motor with a mopar performance cam and 516 heads. I'm thinking the 750 should work fine for this. I'm not racing the car or anything like that it's just a cruiser but I want to use the Edelbrock because it will look close to the original AFB carb.
There was an interesting article in Mopar Action(?) a couple months ago about calculating how to know when you were buying too much carb. It used cubic inches, rpm, and driving style in the calculations. Interestingly, when I did it for my warm 440 and aggresive street use, I still came up with just under 600cfm!!
That of course didn't stop me from going ahead and purchasing the Eddy 800 AVS. However, the plan is to take the 440 from warm to scorching in the near future.
Now is were one of you race guys should step in. Hint. Hint.
The AFB and AVS carbs are great because the air valve secondary action keeps the carb from giving more than the engine needs at any given condition. The TQ works the same way, and the small TQ's were 800 cfm... they came stock on police 318's, 71-73 340's, and 74-up 360's. I don't think a 750 will be any problem on your 383, but a 600 or 650 might give a little better throttle response. FWIW, I bought a Carter (Edelbrock) 750 AFB for my warm 340, and I've been using an 800 cfm TQ on the same engine as a daily driver with no loss in driveability. Go with whatever you get the best deal on.
Last time I did a calculation, the small blocks were 650 CFM (318 to 360), the 383's were 700 to 750, and the 413-440 was up in the 8 to 900 range, depending on the cam shafts, intakes and exhaust.
Joined: Mon Oct 10 2005, 01:49PM
Location: Grand Rapids, MI
Posts: 421
Calculations aside, I have looked at em myself but realworld numbers dont lie.
Ran my near stock 413, cam and headers, with 550 and 625 stock afbs for the longest time.
Got a great deal on a nearly new 750 Carter Comp AFB, and man o man what a difference.
At the time I was running 15.80's. I swapped the 625 for the 750 and the stock intake for a performer RPM. The result was 14.70's and another 2 mph in the 1/4. How much was the carb how much was the intake I can't say, but imho, no big block should ever, and I do mean ever, have less than a 750 on it. <span class='smallblacktext'>[ Edited Fri Dec 02 2005, 08:24PM ]</span>
Frankly I have to agree. At least in the big blocks. I tried a 750 on a mildly modified 360, and it bombed. Had to go to the 650. But on the other hand, I have dropped an 800 on a mile 413 and was very pleased with it. Ran real good. But it was a bit fat at idle
Thats what I'm talking about! It just feels like the old AFB is just holding the engine back from what it can really do. Don't get me wrong the old carb works but is lacking the cfm the engine wants. I really think the 750 will work just fine with a little tweaking on it. It should wake the 383 up especially with the 4-speed behind it.
Joined: Mon Oct 31 2005, 12:48PM
Location: Bakersfield, California
Posts: 1755
If you buy the Edelbrock, be sure to get the Chrysler linkage connectors. You will need it. These carbs are a great bolt-up and virtually need no adjustment once running.
If you have been using an AFB, you will notice one difference: The AVS is an air vacuum secondary, but contrary to what has been wrieen earlier, the AFB is not. The AFB responds to throttle opening, not vacuum. A proper running AFB (which you said your's is not) gives a faster charge than an AVS. Personally, I do not like the hesitation of the AVS or Thermocrap. I've rebuilt them all, and have installed an Edelbrock ona friend's car; I prefer the AFB.
Joined: Sat Dec 10 2005, 04:28PM
Location: United States
Posts: 4954
There had to be a reason for Mopar to use the AFB in the first place. But then again, car manufacturers have to please too many personalities at the same time.
I do agree with Snotty, the Thermodud was a real piece of junk