A driveway carburetor lesson…
The cabrio carburetor, an original style Carter WA-1 324S carb I got on eBay, wasn't quite right. I had bought a rebuild kit for it, but never installed it. I dropped by Peter Brown's Cumberland Avenue Garage this morning to ask if he rebuilt carbs. Turns out he does and would be in my neighborhood this afternoon and would stop by the house to take a look at it on the car.
So he did and he noticed right off that it was running too lean. He also noticed it (a) ran very rich when first started cold and (b) that the automatic choke wasn't opening all the way. That's when the learning began.
This is a 1st generation automatic choke. It picks heat up from the exhaust manifold through tube, which warms up a bimetallic spring. It also has a vacuum operated piston that helps regulate the choke at start up (cracking it open). When we opened the choke cover (air horn), we found two interesting things. (1) the pin holding the piston to the control lever was missing and therefore not functioning, hence the rich initial warm up period (rich until the bimetallic spring heated up). It's linkage was also bent out of shape, which caused the incomplete choke opening. (2) There is a fine mesh brass screen that is designed to filter out any carbon from the exhaust taken off the manifold. My screen was missing altogether and carbon was gunking up the chamber.
Where to get a pin and a screen? Fortunately I have a lot of spare parts, including an unusable carburetor of newer vintage but with the same choke assembly. It provided a donor screen and pin. It took a little doing to get everything apart and reassembled, but it was one of those rare jobs in which everything went very smoothly. Doesn't happen often in my experience, but nice when it does.
Peter's a fellow local car club member and obviously someone who really knows his way around an engine. I'm sure I'll be calling on him in the future. And tomorrow I'll be tearing into the coupe choke to see what it looks like. Almost certainly that screen will need cleaning (solvent and tooth brush did the trick). I've read a lot of information about these cars, but never a word about cleaning that screen.
Here's a picture of him at work on the car.
Also talked with Precision Rubber on Tuesday. He says all his time is going to getting my new cover made and he may be done in a week or so. We'll see.
So he did and he noticed right off that it was running too lean. He also noticed it (a) ran very rich when first started cold and (b) that the automatic choke wasn't opening all the way. That's when the learning began.
This is a 1st generation automatic choke. It picks heat up from the exhaust manifold through tube, which warms up a bimetallic spring. It also has a vacuum operated piston that helps regulate the choke at start up (cracking it open). When we opened the choke cover (air horn), we found two interesting things. (1) the pin holding the piston to the control lever was missing and therefore not functioning, hence the rich initial warm up period (rich until the bimetallic spring heated up). It's linkage was also bent out of shape, which caused the incomplete choke opening. (2) There is a fine mesh brass screen that is designed to filter out any carbon from the exhaust taken off the manifold. My screen was missing altogether and carbon was gunking up the chamber.
Where to get a pin and a screen? Fortunately I have a lot of spare parts, including an unusable carburetor of newer vintage but with the same choke assembly. It provided a donor screen and pin. It took a little doing to get everything apart and reassembled, but it was one of those rare jobs in which everything went very smoothly. Doesn't happen often in my experience, but nice when it does.
Peter's a fellow local car club member and obviously someone who really knows his way around an engine. I'm sure I'll be calling on him in the future. And tomorrow I'll be tearing into the coupe choke to see what it looks like. Almost certainly that screen will need cleaning (solvent and tooth brush did the trick). I've read a lot of information about these cars, but never a word about cleaning that screen.
Here's a picture of him at work on the car.
Also talked with Precision Rubber on Tuesday. He says all his time is going to getting my new cover made and he may be done in a week or so. We'll see.
posted by Bob Shafto at 5:06 PM
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