I just replaced my Holley "Street Avenger" (570 cfm) carburetor with an Autolite "Spreadbore" (roughly 540 cfm) carburetor from Pony Carburetors.

I couldn't believe the difference it made. This was the BEST improvement I have made to my 1985 F150 yet! The carburetor cost me some bacon, but it was well worth it. This carburetor was tuned by Pony from my engine specs like displacement, camshaft profile, exhaust, etc. and was tested before it shipped to me. After adjusting the choke and idle speed, it starts up with only ONE PUMP of the accelerator pedal and it fires up smoothly (and I mean SMOOTHLY) without any hesitations or surges every single time.

Pony informed me that this carburetor has the annular boosters, and has been tweaked for today's gasoline. All gaskets are ABOVE fuel level, so that means no leaks. This carburetor arrived completely jetted and tuned and with a nice electroplated finish. And, it looks a lot like the original Motorcraft 2150 my truck originally came with, so it looks almost stock.

A little costly, but it feels like I am driving a brand-new truck! I am extremely happy with this carburetor! Other than the ONE PUMP is takes to set the choke and start the vehicle, it feels just like I am driving a modern fuel injected vehicle!

 

I've always liked Ford 4bbl carbs (except the 4350 spreadbore carb on the 460).

The 4100 is a squarebore carb, by the way

Glad it worked out for ya. I've heard great things about Pony Carbs.

 

Yes, the Autolite 4100 is a "squarebore" carb in factory specs.

This is an Autolite "spreadbore" (internal spreadbore) carb made exclusively by Pony Carburetors:
http://www.ponycarburetors.com/defau...aqdetail&id=19

Quote:

Pony Carburetors has made the "performance" search much easier. They have recently introduced a 1.12 venturi 4100 that works even better than the 1.08 on small blocks. By narrowing the primary venturi diameter to 1.00", it is now possible to get even better fuel economy, sizzling performance and driveability that begins to approach fuel injection. With the small primary (1.00") and the large secondary (1.18") the Autolite now has the spread bore characteristics that were so desirable and utilized by several carburetor manufacturers in the late 60's and throughout the 70's. The end result of a spread bore design maximizes fuel efficiency while maintaining neck jarring acceleration when the situation arises. Another wonderful thing out this spreadbore is that it can be used on the regular square bore intakes as all four holes are the same size. It is a spreadbore, but INTERNALLY.

 

Interesting. Glad it works well!!

 

I'm building a 351w and I think you've talked me out of a holley and edlebrock.
I'm gonna start looking for an Autolite

 

Just curios, how expensive are they. I have 4 4300's out in my garage and would like to get one of their improved carb's.

 

Mine was pretty high at $400.00. But this was a completely restored carburetor with a "concours" finish. I couldn't find a good core on my own, so this price included the core.

Pony Carburetors went out of business late last year when the owner passed away. Even though their website is still up, they will not return any phone calls, answer emails, and their Ebay store is gone. There are other carburetor shops out there that restores Autolite carburetors, but the "Spreadbore" was something only Pony Carburetors did.