How can I tell the difference between a OEM Slant Six Super Six Carter BBD carb and a 318 V8 Carter BBD? My Carter BBD has a metal tag that reads 8217 0316 and 0-2681 on the carb base. My research indicates that this carb may have been used on the 225 or the 318 engine. I know that some 318 engine carbs had two holes in the throttle plates. My carb does not have those holes. Also, I think there is a difference with the vacuum port underneath the fuel bowl. Mine has a longer metal vacuum tube. What other distinguishing parts help determine which carb I have? What difference does it make if the carb was originally installed on a 318 engine and not a 225 engine? Which vacuum port do I use for the distributor vacuum advance?

Venturi section is tighter on a Super Six BBD which might give better throttle control at low RPM for the smaller displacement 225 engine.

Try slipping a pencil thru the venturi section.
If it won't go thru then that part of the carb would be a Super Six

The following video gives all the itty bitty other carb features to look at to separate the 225 from 318 carb.

Could be your carb has a blend of both which could happen when carb parts get mixed during rebuilds?

http://www.imperialclub.com/Repair/Lit/Films/348/

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads (including the "2 barrels for 6 cylinders" one linked above) are posted here for free download.

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

Fastest way to tell is the nipple for the PCV hose. Straight = 318, bent = 225.

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Casually looking for a Clifford hyperpak intake for cheap.