2bbl motorcraft 2100 ? or new rochesters

[krimepays]

Have a chance to buy a 2bbl motorcraft carb on an intake for 75 -100 bucks. Carb would need to be rebuilt. My rochester are worn out meaning I'd need to rebuild them from the ground up or just replace them. Would be in a buggy in California so I don't see much issue with icing. What do you guys think?

[flat6_musik]

I say GO FOR IT! You'll also be at wide-open-throttle a lot of the time too, which will minimize any fuel puddling. To each his own, but I ran a 400 CFM AFB Carter on the street and didn't mind it much at all.

[krimepays]

They are similar to the Holley from what I understand. Do you have any pics of throttle cable mounting?

[bbodie52]

The typical Holley 4 barrel that is successfully fitted to a Corvair engine is rated at about 390 CFM (Cubic Feet per Minute), but that is divided between the primaries and the secondaries. With a progressive or vacuum actuated secondary the four barrel is not overwhelming the small Corvair engine with too much air volume at low engine speeds. A larger 2 barrel may be less-driveable with too much airflow coming on all at once. A 287 CFM 2-barrel might provide a more tractable engine at low speeds, but may produce less total horsepower at full throttle, because the total CFM capacity is much lower than a 4-barrel with its greater airflow when the secondaries open up.

Most available center-mount Corvair after-market intake manifolds are designed for 4-barrel Carter or Holley carburetors with a total capacity of about 390 CFM. These manifolds are usually designed to mount on 140 hp heads, with four carburetor mounting pads. A 2-barrel configuration may not be optimum for the Corvair because it is a mismatch in its CFM rating (too small in total CFM rating or lacking a progressive division of primary and secondary ports if the CFM capacity of 300-400 CFM is fitted in a 2-barrel configuration). The physical mismatch of fitting a 2-barrel carburetor on a 4-barrel manifold is also a problem.

The CFM rating for the Motorcraft 2100 depends on the model that you have. The venturi size is listed first. Look for the following number sequence in the model number:

1.08" = 287 CFM
1.14" = 300 CFM
1.21" = 351 CFM

Engines to get a 2100 from to name a few:

AMC 304, 360
Ford 302, 330, 350, 360, 351, 390, 400, 429.

Look for Ford/Mercury vehicles from the 70s: Bronco, Comet, Cougar, Maverick, Meteor, Montego, F-250, Econoline, Falcon, Fairlane, Mustang, Torino.

Your total cost for conversion to a 2-barrel must consider the cost of obtaining a center-mount 4-barrel manifold and an adapter to permit a 2-barrel carburetor mount. The cost of fabricating an appropriate throttle linkage for the Motorcraft carburetor, plus the air cleaner and fuel lines will also add to your costs. The final performance of the Motorcraft carburetor will also be an unknown until it is tested. And with too little CFM rating, the maximum horsepower produced may be lower, while too much CFM divided by only two barrels instead of a 4-barrel (or four one-barrels, as with your current 140 hp configuration) may cause driveability problems.



The Rochester carburetors on your engine were rotated 90° for better fuel level control in the float bowls (during aggressive turns). Holley 4-barrel carburetors may do a better job of managing fuel levels in the float bowls in a performance situation. Holley also offers Off-Road Fuel Bowls to help control flooding in an off-road environment. The Motorcraft 2-barrel design is an unknown in an off-road situation, and could be subject to flooding. (My understanding is that the Motorcraft 2100 is basically a Holley design, and many Holley parts can be fitted to the Motorcraft 2100).

Retaining and rebuilding the existing worn Rochester carburetors would provide the least expensive outcome with a known performance potential. Clark's offers kits to help you to deal with worn throttle shafts (see below). Carburetor rebuild kits, all-metal inlet valves, and throttle shaft repair kits may be all you need to improve your carburetor issues.

http://www.corvair.com/user-cgi/catalog ... ow_page=59


http://www.corvair.com/user-cgi/catalog ... ow_page=58

[krimepays]

Brad, ended up just buying two complete carbs for rebuild. These have the original choke and cold idle assembly that mine dont. So I will give them a shot

[krimepays]

Brad, or anyone. Can you tell me why these two carb bases are different?

[krimepays]

One is drilled the other is not. Is one a primary and the other a secondary?