If you need 600cfm, then the 500cfm of the 4100 1.12 Autolite will be to small and cost 10hp or so.
Beyond that my experience, backed up with G-tech and Miles per gallon measurements and winter/summer experience is:
1. The Auto 4100 is very reliable unless you get a really really dirty one. And its usual failings (accel and pump and secondary diaphragms) are easily fixed.
2. But over 300hp, a good Auto 4300 will outrun an Auto 4100, and in fact it will run with a well prepped Holley 600cfm.
3. Ok what is a "good" or "bad" Auto 4300:
4a. The 4300 does not like dirt or crud especially in the hard to clean air horn assembly.
4b. I've had a lot of trouble with the small 470cfm version, but why bother, just use an Auto 4100 instead.
4c. The 1973 and newer 4300A has given me bad luck.
4d. The best running, fastest 4300A's I've had have been the early C8SF, good luck finding one that isn't already tired. Most years from 1968-1972 can be made to run good, I have a very fast D2 version that is bone stock.
4e. The 4300 tends to run lean if you are making much over 350hp or running open headers.
4f. In fact, don't use the 4300 with open headers. I'd be interested if anyone has solved this problem.
4g. But when it's the middle of winter and you want the car to actually start, as opposed to the negotiation proceses inherent to many Holley carbs, a clean early 600cfm 4300 gives peace of mind.
4h. The accelerator pump plunger on the 4300 will dry out and shrink causing a bog and poor starting [no pump shot] but usually soaking in gas will fix this.
4i. I have heard stories of the upper body cracking where the fuel filter screws in - disaster and fire can result. I have never had this happen and have run 4300s for 40 years, but I have heard others that will not run a 4300 for this reason.
If you put a good clean 600cfm 1968-1972 on top of your near-stock 351w thru the mufflers it should run great, and they are good on gas too.
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