Well I bought a good used 1920 off ebay and its the smaller 1920. Problem is the throttle shaft seems to be tighter than my other 1920 that is the larger bore. The truck is a 78 d100 3.55 gears with the 4 speed od. I have a 1945 on it now but can really tell he diffirence with the 1920. So how much would I be losing by running the smaller carb. The engine is 72 225 out of a auto dart.

What do you mean by tighter? In what way is it a problem?
Good difference? Bad difference? Difference in what?
How much what would you be losing? CFM? Performance? Fuel consumption?

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Casually looking for a Clifford hyperpak intake for cheap.

Tighter is a good thing I was being scarcastic. Good diffirence as in it feels like I picked two cylinders. And yes mpg , performance. Iv found on here the cfm diffirence is 75 which seems like quite a bit but have found diffirent asnwers on the web.

A Holley 1920 (of any description) isn't really an appropriate carburetor choice for a '78, anyhow.

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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 engine is out of a 72 dart. Are the metering blocks the same? Besides the throttle plate are the parts the same?

The truck's a '78.
No.
No, the casting itself is different. Not just for the throttle bore size, either; the venturi sizes are different.

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

Ah ok, thank you dan.