Need new carb ! :) Mechanical secondaries

[Sly_drums]

Hello guys, now is the time to change my carb for a new one.

My actual carburetor is a Holley 4150, 600 cfm, square bore, vacuum secondaries. It's mounted on my stock 351C 2V and flows through a Weiand Xcelerator single plane intake.

It actually runs well but I'd like to have more control on the car, especially on the secondaries opening.

I think a mechnical secondaries is the way to go : I always liked what I heard about them. And a spread bore with smaller primaries/bigger secondaries looks real fine to get good gas mileage at low speed and the extra power when you need it (NB : I have no kickdown).

I thought about a rebuilt Motorcraft 4300, they seem to be excellent carbs but so far I've been happy with Holley, so why change ?

I found this dual pumper carb :

http://www.ebay.com/itm/Holley-650-CFM-Double-Pumper-6210-3-SpreadBore-4165-0-Miles-on-Rebuild-Universal-/300876011417?pt=Motors_Car_Truck_Parts_Accessories&hash=item460d9b9799&vxp=mtr

I have a few questions though :

- do you think this carb will mount on a 72 Mustang Grande, and more important : on my intake (Weiand single plane), and do I need a seal or not ?? Looks like no problem to me.

- do you think this carb should provide more "fun" when driving ? I like to have most of the control under my foot. Vacuum secondaries is cool for cruising but I'm more performance oriented I tried to change the vacuum spring to open the secondaries earlier on my actual carb, but didn't really like the result.

Thanks a lot !!

 

[CZ-75]

I believe teh intake would need to be changed to one that has smaller openings up fron and larger openings in back. What you have now is "square," meaning the carb sits on equal size ports. Going to a spread bore, the ports on the bottom of the carb won't mate up correctly to the openings on the intake.

I looked for an intake that would accept a spread bore briefly, but didn't find one.

 

[cudak888]

The 4300 is close to squarebore; the secondaries are 3/16" larger than the primaries. The 4300D is the spreadbore design.

http://en.wikipedia.org/wiki/Autolite_4300_carburetor

-Kurt

 

[Sly_drums]

The 4300 is close to squarebore; the secondaries are 3/16" larger than the primaries. The 4300D is the spreadbore design.
http://en.wikipedia.org/wiki/Autolite_4300_carburetor

-Kurt

Sorry Kurt, I meant 4300 D

 

[Jeff73Mach1]

stay away from the Holley Spreadbore. It is the worst carb holley has ever made.

Instead stay with a square bore and go with a holley 650 or 700 cfm double pumper. New prices are about 50% more than remanufactured and are worth the money!

It will bolt up, is still a 4150 so it should be an easy install. I don't think you will see the difference you are hoping to see though. Get a kickdown lever operational first, it will make your current carb more pleasant.

 

[nosdelacruz]

im still debating mechanical or vacum secondaries. let me know how it goes

 

[Sly_drums]

stay away from the Holley Spreadbore. It is the worst carb holley has ever made.
Instead stay with a square bore and go with a holley 650 or 700 cfm double pumper. New prices are about 50% more than remanufactured and are worth the money!

It will bolt up, is still a 4150 so it should be an easy install. I don't think you will see the difference you are hoping to see though. Get a kickdown lever operational first, it will make your current carb more pleasant.

Already heard about leak problems on those carbs... What do you think of this one ? (same with manual choke and quare bore)

http://www.ebay.com/itm/HOLLEY-CARBURETOR-650-CFM-DOUBLE-PUMPER-w-MANUAL-CHOKE-REMAN-0-4777-/321086305495?pt=Motors_Car_Truck_Parts_Accessories&hash=item4ac23c34d7&vxp=mtr