Edelbrock AVS2 Carb Dilemma

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1969SWINGER340

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I am looking to purchase one of the new Edelbrock AVS2 Carbs. I am trying to decide the best CFM Rating for my application. The 1901 - 500 CFM or the 1906 - 650 CFM.
I Have a Duster 1973 318, Stock heads, Edelbrock LD4B Intake, Comp Cams High Energy 268H, Stock exhaust manifolds, Dual exhaust with Turbo style mufflers, 833 Overdrive 4 speed, with factory 2.94 rear gear. The Car is a weekend cruiser just for driving fun with the occasional romp to 5500 rpm. I do not want to over Carb, but I don't want choke the engine down either. I am looking for the groups thoughts and experience.
Thanks for the Help.
 
I would recommend a 600-625 cfm carb for your setup. 65'
 
The 1906 all the way, The air valve secondary will only let the engine pull as much air as the engine can use.
 
I contacted Edelbrock and they stated that the 1901 500 CFM AVS2 was correct for my application, and that the 1906 650 CFM AVS2 would be on on the large size for that engine combination. The Carb CFM Calculators I have viewed online show just slightly less than 500 required CFM for the mainly stock 318 at 6000 Max RPM @ 85% VE. I do not want to over Carb the Car, but I do not want to choke it down either. The Edelbrock LD4B Intake has such large runners considering the overall port size of the stock 1973 318 heads, and I thought this intake may be able to take advantage more with the 1906 650 CFM. The Groups thoughts? Thanks
 
Here is Just one of the CFM Calculators

Carb CFM.jpg
 
In high gear your effective rear axle ratio is 2.29 to 1. By your description of mostly cruising highway car with occasional quick romp to 5500, I’d go with 500 cfm and get a little better mileage. Those runners go down to 318 ports at the exit, but that’s one of the better manifolds for a 318. I’m sure the engine would run with the 650 better if the car had lower gears and a close ratio transmission, but the 500 will help out the lower rpm with the wide ratio spread of the OD transmission. Following the rules of Rusty’s guide to hot rod bliss on this one. Either way, the engine will only pull as much air as the secondary air door spring tension will allow. May as well keep the primaries as small as possible for cruising with a combination that mild
 
I agree with the 500. The stock exhaust manifolds are going to really limit how much it can breath regardless of the intake. With headers I might go with the 650 but the 500 will do everything you will need even with them. I doubt you'll spin that thing to 6k much and if you put a 5000 rpm limit in that calculator it will ask for about 400cfm.
 
1969SWINGER340 said:
I contacted Edelbrock and they stated that the 1901 500 CFM AVS2 was correct for my application, and that the 1906 650 CFM AVS2 would be on on the large size for that engine combination. The Carb CFM Calculators I have viewed online show just slightly less than 500 required CFM for the mainly stock 318 at 6000 Max RPM @ 85% VE. I do not want to over Carb the Car, but I do not want to choke it down either. The Edelbrock LD4B Intake has such large runners considering the overall port size of the stock 1973 318 heads, and I thought this intake may be able to take advantage more with the 1906 650 CFM. The Groups thoughts? Thanks
Click to expand...

You've already gotten the group's thoughts and I concur. 650 all the way. You spoke to someone at Edelbrock who probably doesn't even know how carburetors work, much less THAT particular carburetor. This is why I HATE when people try to make a certain formula fit every application. There's no formula in the world that can do that. Your combination begs for more than 500 CFM. That's the size carburetor Chrysler put on the Hyper Pack slant six......and it was a 170. What's that tell you?
 
Those who say go the 500........what if he wants headers later on? What if he wants to upgrade the camshaft? What if he wants to swap in a mild 340 or 360 later on? Then, he has to get a whole nuther carburetor, instead of being able to step the tune up on the one he already has. That 650 would feed a mild 408 with the right jets and rods, yet in stock form is perfect for his 318, IMO. At the very worst, he'll need to swap in larger metering rods to lean it out a little on the primary side. That's my opinion and I'm stickin to it.
 
650 all the way. I bet you still get darned near 20 mpg on the highway. Hell, I have a 600 AFB on my 273 and it loves it. Your 318 can handle a 650 especially the AVS2
 
Neither......Edelbrock 1405 600cfm.
People are almost handing them away, and it will work perfect on your 318. Get yourself a 650 AVS2 when you move up to a 340/360.
 
Johnny Dart said:
Neither......Edelbrock 1405 600cfm.
People are almost handing them away, and it will work perfect on your 318. Get yourself a 650 AVS2 when you move up to a 340/360.
Click to expand...

That's a pretty good idea!
 
I picked up mu 600 AFB for $100 at a swap meet. Bolt on and go! Yes, nice carb for a teen. The AVS2 sounds intriguing. It could be fun once it's tuned.
 
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