The Ford Barn

JayJay · 01-02-2021, 01:38 PM

All - I'm into my Zenith-2 carb and have a couple of questions I'm hoping you more experienced folks can help me with. Car started and ran OK before I began, but the carb is really rusty and gnarly looking, and there was a lot of crud in the glass sediment bowl, so I figured a good cleaning and rebuild was time well spent.

1. Throttle shaft bore tolerance. My throttle shaft measures 0.280"+, nominal is 9/32" (0.281"). Bore in the carb casting measures (gage pin) 0.287", and it feels a bit sloppy. The oversized shaft available from the vendors is 19/64" (0.297"), so I'm a long way from that.

I can see maybe 0.002"-0.003" for a slip fit, but given that this is a somewhat hostile environment under the hood, is 0.006" unreasonable? I could find some brass tubing, overbore the casting and ream to fit I suppose, but I'm more interested in how far off the mark these numbers are.

2. Main mixture seat (bottom of the choke rod). Mine is cast into the carburetor body. Looks a bit cruddy. How does one clean this, given that it can't be removed? I found a package of wooden BBQ skewers with a long tapered point that I used (with a bunch of brake cleaner) to rotate in the seat, and got quite a bit of crud out. Is that good enough (repeated often until clean), or is there some other magic? This is a relatively large hole, compared to others, and adjustable, so I suppose you live with what you can get, but I'm open to other suggestions. I will be replacing the needle with the new one I got in the rebuild kit.

Thanks, all. Happy New Year, and stay healthy.

JayJay

01-02-2021, 01:38 PM	#1
JayJay Senior Member Join Date: Jan 2020 Location: SF Bay Area Posts: 1,075	Zenith Carb Questions All - I'm into my Zenith-2 carb and have a couple of questions I'm hoping you more experienced folks can help me with. Car started and ran OK before I began, but the carb is really rusty and gnarly looking, and there was a lot of crud in the glass sediment bowl, so I figured a good cleaning and rebuild was time well spent. 1. Throttle shaft bore tolerance. My throttle shaft measures 0.280"+, nominal is 9/32" (0.281"). Bore in the carb casting measures (gage pin) 0.287", and it feels a bit sloppy. The oversized shaft available from the vendors is 19/64" (0.297"), so I'm a long way from that. I can see maybe 0.002"-0.003" for a slip fit, but given that this is a somewhat hostile environment under the hood, is 0.006" unreasonable? I could find some brass tubing, overbore the casting and ream to fit I suppose, but I'm more interested in how far off the mark these numbers are. 2. Main mixture seat (bottom of the choke rod). Mine is cast into the carburetor body. Looks a bit cruddy. How does one clean this, given that it can't be removed? I found a package of wooden BBQ skewers with a long tapered point that I used (with a bunch of brake cleaner) to rotate in the seat, and got quite a bit of crud out. Is that good enough (repeated often until clean), or is there some other magic? This is a relatively large hole, compared to others, and adjustable, so I suppose you live with what you can get, but I'm open to other suggestions. I will be replacing the needle with the new one I got in the rebuild kit. Thanks, all. Happy New Year, and stay healthy. JayJay __________________ JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan Last edited by JayJay; 01-02-2021 at 02:26 PM.