Hoping someone can help me out. 1980 Plymouth Volare slant six Holley 1945 one barrel. Just replaced old carb with a newly rebuilt one purchased from Rock Auto (I have used these before with no issues; maybe I was lucky?). When tightening down the fuel line, the cheapo needle seat they used split in two. I replaced it with the original one and car ran decently for a day of driving around but now it won’t start. I am not seeing or hearing any gas getting into the carb—presumably the old needle seat is sticking closed. Gas is definitely reaching the carb but not getting in. Does that sound like a reasonable conclusion? Also, I’m seeing two options for replacements—they differ on orifice size and possibly on length. Which one would be correct for my carb? This is just a periodic drive-around-town car for now. Thanks in advance.

It may be reasonable to conclude that the needle and seat are stuck..

Have you pulled the carb off, to investigate? It would seem that the culprit would be obvious once you are looking at the float bowl, if there is something amiss..

Also what was ailing the old carb? Can you combine the two and come up with something that works?

Sometimes several light taps with screwdriver handle at area next to fitting will free up the needle
and float

Yup, you were unusually lucky. "Remanufactured" carburetors (you didn't buy a rebuilt) tend to be junk.
De luxe!
Sounds like it. See if there's a Daytona Float Valve for your application; they work better. In the long run, you'll probably want a better carburetor. Two good, fully-compatible, new carbs: this and this, or I have a compatible final-year (1974) Carter BBS on the shelf; send me a PM.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Many thanks for the excellent guidance. I found a new replacement needle seat with the .082 orifice--bolted it on carefully (lesson learned) and so far, so good. Time will tell. I will look into the Daytona Parts Co. options--thank you for the tip!

Thanks also for the tips on different carb options; will keep those in mind. Seems that if one buys a 40-year old NOS carb, a rebuild would be in order, correct? Do you have any recommended vendors for that service? Or kits (if I decide to try the DIY route)?

I am hoping to ultimately put a fuel injection set-up on this one but I wanted to first confirm that it was a worthy candidate before I spend too much for a change.

Thanks again.

Unlikely that the carbs that Dan is suggesting would need a rebuild as they are "new old stock"..

For the educational experience I would try to carefully rebuild the worn out one you have first.. and likely it would be better than a re-manufactured carb.... IF done in on a neat, clean workspace, in a methodical and unhurried manor, depending upon what was ailing it, you could have a good running carb for the price of a kit.

I have only ever used napa echlin carb kits. I've never had a problem, but there are better kits out there..