Carb question?
Post Fiend
Joined: Dec 2007
Posts: 8,521
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From: Lost
It's more than needed, but will work fine with proper tuning. If you're looking at buying new, I'd consider a holley 390 or 465, or an edelbrock 500. If buying used at a decent price, or already own the holley 600, then by all means, it's worth trying.
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
https://www.ford-trucks.com/forums/9...n-it-work.html
Your question is basically answered in that thread.
"...reading on here that the 240/300 doesn't create enough vacuum for a 600cfm???" Where did you read that?
I'm just guessing at what you are talking about but the vacuum canisters you mention are for high performance engines with long duration and wide overlap cams...the cams cause the drop in manifold pressure (vacuum) and vacuum operated devices like brake boosters won't operate properly without sufficient vacuum thus the canisters to "store" the vacuum.
Holley's eBay store/auction will list the 1848/465cfm 4v carb from time to time.
Your question is basically answered in that thread.
"...reading on here that the 240/300 doesn't create enough vacuum for a 600cfm???" Where did you read that?
I'm just guessing at what you are talking about but the vacuum canisters you mention are for high performance engines with long duration and wide overlap cams...the cams cause the drop in manifold pressure (vacuum) and vacuum operated devices like brake boosters won't operate properly without sufficient vacuum thus the canisters to "store" the vacuum.
Holley's eBay store/auction will list the 1848/465cfm 4v carb from time to time.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
You see, it doesn't matter what type of engine the carb is sitting on, the secondaries will not open until the primaries reach near-peak velocity.
Also, it doesn't matter whether the engine makes much (if any) manifold vacuum at idle. It's not manifold vacuum that operates the vacuum secondaries. They are opened by "Venturi Vacuum", which is directly related to the volume of air flowing thru the venturi(s) of the carb.
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Lead Driver
Joined: Mar 2008
Posts: 7,188
Likes: 384
From: Near Los Angeles
The 4100 came in two sizes. The 1.08 venturi size (stamped on float bowl), which is 480 cfm, and the more common 1.12 venturi, which is 600 cfm. Either one is more than 40 years old! If you get it cheap--and I mean for about $50--then I'd say give it a whirl. The 480 cfm works great.
However, because of Pony Carbs, and all the mustang oem restorations, the price on replacement parts is high. If you are unsure, I'd say to go with a carb that is MUCH newer, and therefore less likely to have issues.
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Elder User
Joined: Oct 2008
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The annular boosters used in the primaries of the autolite 4100 or in some of the holley carbs makes a significantly stronger booster vacuum for a given airflow through a given venturi bore size. You can use larger carbs withouth detriment to low end trottle response. For a carb that uses straight leg or dog leg boosters 600 CFM is probably too large for a street driven 240 IMO. I personally feel that the Holley 390 is too small for 300 inch motor, but for a hopped up 240 I would seriously consider it.
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