Hamilton

Oh, I think you'd have figured it out. Well, you might not have figured out the actual issue, but you'd have eventually solved it by changing out the cap and rotor which, even if you didn't realize it at the time, you'd pretty much narrowed it down to.

This exactly the unit I use. After the one I'd had for about 35 years took a dump, I found this one at a garage sale for fifty cents. Being a cheapskate at heart I offered a quarter, which they readily accepted.

Absolutely true - particularly given that you've yet to install the rods and pistons. As it sits, your crank should spin quite freely. _

I was in Oregon visiting my folks and hadn't ridden the old Canby Ferry for a long time, so I went to the SMS warehouse. If they still offer fabric creation, and if you're seeking originality and don't mid spending a little extra top get it, there's no need to settle for "a close match".

Ten years ago anyway, the owner of SMS Auto Fabrics (Canby, Oregon) also owned a textile mill in the Carolinas. At the time SMS was, and might still be, the largest repository of OEM auto interior fabrics anywhere in the world. They didn't have the correct broadcloth wool for my `49 Plymouth but did have a sample book, the swatch from which was a perfect match to the piece I brought with me to their shop (pulled it from under where the front seats folds forward, so it was effectively still like new). I left them a deposit and was told it would take about three months. It ultimately took six but they absolutely nailed it: the weave, the color, the pattern, all spot on! At $90/yard they didn't give it away, but all in all, I thought it was fair, given that they literally had to create the fabric from start to finish. Your car probably came with mohair but if they can reproduce the broadcloth wool I suspect they can handle mohair. If you're looking for originality, I doubt others can match what they can (or at least used to) offer.

^^^ This. Tighten slowly and if you're paying attention you can feel the "give" when it crushes. Tighten the plug only ever so slightly after feeling the washer crush. Too much and you lose the seal. This is also why re-using is not recommended. _

Yup. Started pumping gas as a high school freshman - back when hustle was the name of the game. Checked and sold oil, mounted tires, washed windshields etc. As a junior I took a ration of shit from people when gas prices spiked (to about $0.37/gallon if I recall) as a result of the Arab oil embargo. Like a high school kid had anything to do with it ...

Glad it turned out to be so simple. _

As someone mentioned, we're kind of flying blind here, but I suspect (coincidences happen, after all) that you have more than a single issue to identify/address. I was trying to think of whether there was any way possible for an accelerator pump to act up so badly that it would inject fuel briefly at start up (causing the brief spike in RPMs you mentioned) but then not deliver it upon acceleration (causing the backfires). However, given that you said both carburetors worked before, but neither does now, other than a possible leak at the mounting point, we might safely assume that component isn't an issue, which is why I think you're dealing with more than one. The inability to idle without constantly working the throttle and the 2K idle when holding the choke closed both speak to your air/fuel mixture - the likely culprit, as mentioned in earlier responses, being a vacuum leak. The good news is that the number of locations for a vacuum leak to occur is pretty limited on these old flatheads. Still, you need to diligently and carefully check them all. You're probably also looking for an electrical and/or timing issue. Worn or sticking distributor components can cause backfires, as can something as simple as a hairline crack in a distributor cap. It's just a matter of testing and eliminating one potential culprit at a time. On the subject of backfires: it shouldn't be too difficult to identify the source. Obviously, the direction from which the sound came is a major clue. If you're uncertain of that, think back in your mind's ear to how they sounded. A carb backfire is more of a popping sound (sometime pretty loud, to be sure). On the other hand, tailpipe backfires are typically more of the BANG! variety and can even sound like gunfire, an attribute I wouldn't associate with one emanating from a carburetor. Good luck! Let us know what you find.

Here's my contraption. A factory steel cap, drilled and threaded. I figured I might as well use an old valve left over from some long-ago vehicle. This, combined with a vacuum bleeder and a lift makes short work of brake bleeding. edit: the rubber line in the background is part of the lift, not the bleeding system,

Yes, bias ply tires are less expensive. I bought a set of Cokers last fall, shipped to my home for just over $700 shipped to my door, including tax. Understand though, I don't drive the long distances you mention. If I did, I'd have spent the other few hundred dollars on radials. _

^^^ I have to connect the power and ground leads to my battery charger, as my timing light won't function on six volts. _

Given the low cost I went with one of their coils. _

Definitely call versus trusting their online catalog. Here's the one that worked for my 6V positive ground '49 (same part no. PLODGE referenced above): https://www.amazon.com/gp/product/B001CMX3QS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Works perfectly and installation is a simple affair. _