Model-A Carburetor Upgrade

The stock Model-A carburetor is a very simple one-barrel updraft carburetor.  No accelerator pump, not a lot of circuits and adjustments, but it works surprisingly well in practice.  It even has a nifty control in the cockpit that allows you to pull a knob for the choke, and twist it for mixture.  And this control can be easily disconnected at the carburetor with the sliding of a sleeve.  The carb fills from gravity since the fuel tank is behind the dash, and the carb is mounted down on the side of the motor.  Looks like this:

The real problem is that it gets terrible gas mileage.  Around 13-15 MPG.  Pretty poor for a 2,200 lb car.   I had read that you can improve mileage and power by installing a more modern carburetor, the Weber DGV.  This is a two-barrel, progressive-linkage carb with accelerator pump, and all the circuits that make modern carbs work well in a variety of conditions.  And I happened to have one of these carburetors sitting around from when I converted my Austin Healey Bugeye Sprite from the Weber back to SUs.

Typically Model-A Weber conversion kits are available as a complete package, but since I had the Weber already, I could only find one place selling the manifold and linkage kit separately.  It's Auto Care and Restoration in Redding California (  Nice people, but it took about a month for the order to be filled.  Then later I found that they hadn't shipped part of the linkage, so had to wait for that too.

Since this is a downdraft installation, the carburetor is mounted quite a bit higher on the engine.  Enough so that it's a concern whether gravity feed is adequate since the static-head is much lower.  I understand some people do run these on gravity, but most install an electric fuel pump.  While that's probably the best way to do it, I decided that since my Model-B motor had the boss for a mechanical fuel pump, I'd use one of those to be more in keeping with the vintage nature of the car.  The person I bought my car from set me up with a box of random Model-B fuel pump parts.  Since I didn't like the looks of the lever arm on any of them, I decided to send one off to Renner's Corner in Manchester Michigan ( for a rebuild.  I got a call back that this wasn't a Model-B pump, it was from some sort of industrial engine.  I thought it was sort of unusual that the mounting pattern looked the same, but learned that there was an ANSI standard for fuel pump mounting that applies to the flange (but not the lever).  Great idea, wish there were more common parts.  That probably explains why a small-block-Chevy fuel pump block-off plate fits the small-block-Ford engine that I'm building for my 240Z.

I sent the other complete pump, and the body that I had remaining, off the Renner's Corner.  Turns out the complete pump wasn't for a Model-B either, but the body was.  By the time I purchased the parts from Mr. Renner to make the pump complete, and added the cost for the two shipments of core parts to him, it would have been cheaper, and a lot faster, to just buy a complete fuel pump without any core.  Well, live and learn.

The Weber has a modern, chrome air filter assembly that isn't all in keeping with the Model-A engine's appearance.  I bought a small old oil-bath filter at a swap meet, hoping that it could be modified to work, but the carburetor is so close to the hood on the side, it wouldn't fit without being mounted way off center.  I found an aluminum carburetor inlet at Pierce Manifolds (  It's intended to be used with a hose for a remote inlet, but looks pretty vintage used stand-alone.  Especially after I painted the intake manifold and air-inlet with good old Ford engine green like the rest of the motor.

The fuel line is 1/4" OD, which doesn't deliver a lot of fuel (3/16" ID?), but evidently it's enough.  The fuel bowel and fuel pump use special compression fittings.  They are available at NAPA or CarQuest as "Ford Fittings."  I also got a choke cable at NAPA and ran it up to where the choke tube was mounted originally.  I had to make a little aluminum spacer at the top to extend it out a little from the bracket.  Here's what the completed installation looks like...

I took this opportunity to mount the "heater" that I got with the car, but was just in a box of parts rather than mounted.  It was missing a couple of parts that I fabricated.  This was a period accessory since the standard Model-A had no heater.  You can see it as the large aluminum duct directly behind the carburetor.  It works by routing air, pushed by the fan, through the ducting which encompasses the hot exhaust manifold, then sends it through a hole in the fire-wall that can be easily opened and closed.  From inside the car, it looks like this...

The heater works amazingly well, although I suppose it's sending some carbon monoxide into the cabin if the exhaust manifold is leaking at all.

I haven't actually driven the car with the Weber yet, I'm still waiting for the last part of throttle linkage that they are sending me.  

Update:  After three weeks of waiting for the throttle linkage part, I gave up and found something that could be modified to work from a Volvo at Pull-A-Part.  I've driven the car now, and it seems snappier with the Weber.  Fires right up like it can't wait to run.  I'm happy with the conversion.

Epilog - it's many months later now, and I never did get the linkage parts, but don't need them anymore, anyway. After driving it for a while, I discovered that it didn't turn into a Toyota Prius when it comes to economy. Just a little better than stock now.

Model-A home...