It dawned on me tonight that I am using the carb off of the 170 engine that came out of my car, on the 225 that I put in the car.

Is the jetting different between the two? Do I run the risk of running too lean and hot?

Also, what is the single adjustment screw at the bottom of the Carter BBS. I bought my FSM for the 79 engine. No BBS info there:)

Thanks guys,

Chris E.

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

A 170 BBS will have a smaller 1 9/16th throttle "blade". (butterfly)
The jetting will be correct but the carb will flow less air.

The screw at the base of the carb. is used to set the idle air / fuel ratio.
DD

There's no jetting incompatibility. Elaborating on what Doc says, the 170 carbs used through '66 had a 1-9/16" throttle bore. This small-bore carb was also used on taxi-spec 225s to save on fuel. The larger 1-11/16" carb was used on regular 225s, and on 170s starting in '67. You can measure the throttle bore diameter at the bottom of the carb to determine which size you've got. Of course, at this late date the odds are against your looking at any particular engine's original carburetor.

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

The 1965 automatic trans, 170's, had the larger carb, also. don't know about other years.
Had to prove this to NHRA back in 1974.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

My '65 FPCs and FSMs say they got the smaller one, but it's entirely possible some of each left the factories.

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

In 1965 the 170 standard shift got the small carb. The 170 automatic, and all 225's got the large carb.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Theoretically, the smaller carburetor is more efficient because of better vaporization efficiency in the narrower venturi. Peak horsepower at wide open throttle at high rpm is reduced 5% with the 1 9/16 carburetor vs the 1 11/16. Even the large carburetor is rather small even for a 170 engine; they used these for low initial cost, trying for the best compromise of efficiency vs. power in a single venturi design. This is why people get such good results with the 2 bbl. "super six" carburetor; the two venturis are each smaller than the one on the single bbl., but the total area for two is greater. Therefore, better efficiency and greater maximum flow, both, but more expensive to manufacture. Slant six carburetors also suffer because they had to be specially designed for these cars (low height), hence a short venturi, to fit under the low hood, for body styling purposes. Long venturis are more efficient, and tall carburetors were common on old cars with high hood clearance.

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1964 Dart 225 1966 Valiant 225
1966 Dart 273 1966 Barracuda 273
1969 Dart 225
'64-170 engine '66-170 engine
(two) 198 crank/rod sets in custom-fitted wooden boxes

wooden motor scooter with hybrid-electric drive

Thanks everyone. Great info!

Chris E.

_________________
-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!