Same thing.
There are several here running the 500 (which should be readily available), if you're lucky, you can score a vintage "competition series" Carter in 400cfm (model 9400, I believe). .....or you can locate an OEM AFB like I did for a '65 Dart 273. It flows 400cfm.

D/W

_________________

If it ain't broke, fix it!

OK, now the next question becomes:

500cfm AFB? Or 650cfm AVS?

440_Magnum...?

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well, I have an OPINION on that... but since I don't currently own anything smaller than a 318 (at least not with a carb) I don't have much data.

My feeling is that both a 500 CFM and a 650 CFM are both a lot of carburetor for a 225 CID long stroke torque motor. Given that both will be operating in the over-carbed zone, I'd go with the AVS even though its bigger. The AVS is a lot more forgiving about oversizing it for an engine, just like a Thermoquad is. Case in point: my 318 never had a truly smooth transition onto the secondaries of a 600 CFM AFB. But when I put a Thermoquad on it (750-800 CFM, depending to whose rating system you believe) it was MUCH smoother because the TQ is an air-valve secondary carb like the AVS and Quadrajet, even though the over-carbing was worse. When I put the AFB on my 383, it was perfectly smooth because it wasn't over-carbed.

My rule of thumbs are 1) err on the side of undersizing a carb, and 2) if you know you're flirting with over-carburetion, use an air-valve secondary Carter, Edelbrock, or Rochester or vacuum secondary if you must go with a Holley.

_________________

I vote adapt an AVS top on the 500. The new AVS's are overpriced. I think any old OEM AVS top could be modified lightly (the air flap where it needs to clear the booster venturies) to work. I keep saying I'm going to try this, but just haven't gotten around to it yet. The spring-loaded AVS air door is definitely superior to the standard AFB weighted door.

D/W

_________________

If it ain't broke, fix it!