My car is not running real smooth at a steady speed. It seems to surge foward a little bit on a regular rhythmic basis. It idles smoothly and i don't notice this unless I drive at a steady sustained speed. It does not do it while accelerating or decelerating. Any ideas?

It sounds like you are describing "lean surge". If your carburetor and engine are stock, that shouldn't occur. If you have a modified engine, you might have to re-jet the carb.

Yep, lean surge. But you've got a '73, which was originally equipped with EGR (exhaust gas recirculation), an emission control device which can cause the same symptom. Whether it's caused by a carburetion issue or an EGR problem, it's basically the same problem at work: the cylinders aren't receiving a rich enough mixture. Can we have some details on your car? Is it stock or modified? Running the original Holley 1920 carburetor, a remanufactured version of same, or something else? All vacuum hoses and emission control devices hooked up, or some of them bypassed? How many miles on it? Any recent work we should know about, especially on the fuel or emission systems? When did this problem first appear, and did it appear suddenly, or gradually? This information will help us steer you in the right direction to find and fix the problem.

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

I've experienced this from having the float level in the carb a wee bit too low.

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some is good,
MORE is better,
and TOO MUCH, is JUST ENOUGH!!!!!!

Super Six, Reman 318 BBD, Headers, Comp Cam 264, Home Ported Head, EGR Block Off plate, Fresh Motor about 4000 miles

If I leave the car idling, it will leave black on the concrete from the tail pipe. This has made me think it might be running a little rich.

I'll check the float level soon. Thanks.

A carburator has at least 3 "circuits" that control the mixture at different engine RPMs and loads. (idle, light load & power)

It is possible that the idle circuit is running rich and the light load, cruze is on the lean side.
DD

You will likely discover this is at least partly to blame for your troubles. Remanufactured carburetors, in general, are junk.

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

I had the exact sounding problem, surging, mine idled great, same symptoms as you describe. I found what looked like spider web(I think old gasket material) in on of the jets, hosed out the metering block with carb cleaner put it back together and it runs great.

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Excuse me, does this smell like chloroform to you?

Do you have a vacuum gauge on your car?
If not, get one. Then tell us the vacuum range it is surging at......
Then you can attack the right circuit, as Doc pointed out.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Any suggested reading on carter bbd? All I have is a Factory service manual and did not find it that helpful.