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4100s were phased out throughout the 67-68 model year in favor of the 4300, IIRC. 4100s are good carbs (Mid and I both have one... ;) ) but not original for the 351. If it's a 1.12 venturi, it may be big enough. A 1.08 will probably be marginal at ~480CFM.
Daniel
 

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Yep, Autolite 4300 it was....
 

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BornInAFord said:
4100s were phased out throughout the 67-68 model year in favor of the 4300, IIRC. 4100s are good carbs (Mid and I both have one... ;) ) but not original for the 351. If it's a 1.12 venturi, it may be big enough. A 1.08 will probably be marginal at ~480CFM.
Daniel
1.12 venturi? That's a new one on me. As far as I know there was the 1.08 and the 1.21 that came with the introduction of the 1968 351 and 390 series engines. If I am wrong, please correct me.
 

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1.08 was the small one
1.12 was the bigger one (hipo and others)
There is an even larger one from 58/59, but
they are definitely rare. (I don't recall the
venturi size on the last one) They pop up
on Ebay from time to time.
 

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As stated, a 4300. Much more complex and difficult to rebuild than a 4100. And IMO doesn't run as well.
 

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Discussion Starter · #10 ·
Thanks,I have done much reading since my post.I know now it is a 4300,and that the are not good carbs.SO,I guess what I need to know is what carb will work with my setup?
 

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Depends on your setup. The Hipos came with 480s (1.08) from the factory and they ran well. Shelby put bigger (780?) Holleys on his cars because of the higher RPM requirements and deeper breathing according to many of the written articles I have read. The 600 CFM 4100 version 1.12) were on the bigger Ford engines. I currently use an Edelbrock 600 CFM on my modified 302 with a T5 and semi-deep rear gears and it runs well. I have a 480 CFM 4100 in the garage that I might play with on the next build.
 

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Yes Shelby used the 715 CFM Holleys IIRC, but they tended to be overcarbureted IMO. I have an old Road and Track 1965 road test of the first GT350, and even they commented on how it always tended to load up and need a good stab of the gas to clear its throat as they drove it around town.
Stay with 500-600 CFM and you should be in good shape.
 

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Are you sure the engine is a 351W?
 

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I took five Autolite 4100s to a local speed shop. One 4100 had the small 1.08 primary venturi and the rest had the larger 1.12 primary venturi. The small one flowed 441 CFM, the larger ones flowed 503 to 528, averaging 520. These results were very close to what I expected for the 1.08 but 50 CFM higher for the 1.12. Still the 1.12 does not flow 600 CFM as claimed by some vendors. The 1.21 is the large primary venturi on a a Motorcraft 2100 carb.
 
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