Re: Cater carburetor tools/metering rod adjustment

Posted by DavidPackard On 2024/3/18 22:22:54

Moodydavid16

Setting (or at least checking) both the metering rods and the anti-percolation valves is a necessary step when re-building a WDO that you otherwise have little experience with. If the carburetor had been running well and then abruptly has an issue, that’s another issue and the two aforementioned checks are less important, because just before the issue all was well and the adjustments were likely close to correct.

An engine that starts and then stalls is not likely either the metering rod position or the anti-percolation valve position. I would go after the choke and high idle adjustments. Being a WDO I’ll assume you have the throttle position starter switch . . . therefore the engine fires with a rather large throttle position, and once fired you likely reduce the throttle position as close to idle rapidly. My ’48 would have the same symptom until I installed an auxiliary starter switch, and tinkered with the choke and high idle adjustments.

Back to the rod and valve adjustments. I found a T109-113 for sale on EBay. I looked today but did not find one in the first page or two when I searched for ‘Carter tools’. Update: I see HPH found one . . . jump on it! It’s not clear to me where the 2.28 inch dimension is measured . . . I think it is from the ‘flat’ to a location on the ‘pointy end’ that has the same diameter as the main jet taper.

What I found was a late lifting metering rod adjustment results in a bog during the transition to the main metering circuit (fuel starvation by reduced fuel flow area). Late closing AP valves also has the potential of producing a bog in the same transition point (fuel starvation by reduced suction at the discharge nozzle), but if the AP valves are significantly late closing the engine will not transition to the main circuit at all, but you might be able to rapidly accelerate to the main circuit. I have not explored early rod lifting (likely a rich transition), or early AP valve closing, which may cause a hot restart difficulty, but I’ve been running my ’48 with a set of dummy AP valves for many years, so early closing AP valve may be undetectable form the driver’s seat. I’ve also have had some success shimming the vacumeter spring with a #4 machine screw AN washer.

Stalling just after start, in my experience, is a choke and high idle throttle position issue . . . assuming all else is proper, such as timing, tune-up, etc. You should find in the Carter documentation guidance on bench adjusting the high idle position.

Update:

On Carter tool T109-113 the 2.280 inch dimension appears to be the distance from the step in the tool to approximately half way down the tapered tip.

If I had to guess I would predict the print calls out a tip angle of 45 degrees, and begins approximately 2.220 inch from the step. The full width of the tip is approximately 0.132 inch, and appears to be fabricated from 16 gauge sheet stock.


dp