Hey, you guys:

Car is a '73 Dart Custom 4-door, Holley 1920, auto trans, 111k miles. Typically using middle-oct fuel. Since acquiring the car in Oct 2010, I have:

1. replaced the carb with a reman from National Carburetors (Jacksonville, Fla.)
2. had the timing chain/gears replaced
3. put the engine timing back to near-zero TDC (Couple degrees adv) from the approx. 10 degrees BTDC the previous owner had it at.
4. adjusted the idle mixture according to the procedure in the green Haynes manual with the Diplomat on the cover.

None of this has addressed the symptom I've had since acquiring the car, which is really bad bog/hesitation when accelerating from dead stop after startup and warm-up. Engine nearly dies, then recovers. Same problem when attempting a hard acceleration from a lo cruising speed (like 20 or 30 mph). The problem does not go away until about an hour into driving; during that hour or so, have to feather the accelerator a few times to get the engine to respond non-boggily. It will respond like it should after feathering. After that hour or so, the problem goes away entirely - as if the problem never existed (excellent response from dead stop).

No problems with startup/warm-up in the morning while stationary. EGR vacuum line is plugged with a little bearing-type ball right before line reaches the valve nipple. OSAC valve is bypassed. Don't know if any of this is relevant.

Thanks for your help. Looking forward to hearing from everybody!

Danny in Miami, FL

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Is the vacuum advance system functioning?
DD

Oops. "Remanufactured" carburetors are frequently very troublesome. You will likely have to pay some attention to it, and even that may not fix it. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.
Haynes manuals are useless (full of bad info) even when you're using the one that actually applies to the vehicle you're working on. Throw it away and get the books described in this thread as quickly as you can. In the meantime, follow the adjustment methods linked from the carburetor post, and tune-up parts and technique suggestions in this thread.

It's an interesting problem you've got. It sounds carburetor-related. If it were choke-related, it would go away much sooner than an hour. Have you checked to see if your manifold heat control valve ("heat riser") is working? Are you running a 180° or 195° coolant thermostat that's working correctly?

0° timing also has a way of creating flat spots. Try 5° BTDC and keep your ears open for ping. If none, try 7° BTDC.

Do you have any other symptoms? Rough idle, hard starting, anything like that?

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

Will have to verify vacuum timing advance operation; hadn't thought to check that.

I realize that I was inviting calamity upon myself in installing a reman carb, but with NOS 1920's being as rare as they are, I had little choice. I will check out the techniques and lit as suggested, Dan.

With regards to rough idle, I have always thought that the engine idled a little rough, even when plenty warm. I just attribute it to little vacuum leaks here and there that I'm guessing have accumulated over time. Engine operation is satisfactory enough that some single big vacuum leak is not indicated.

Will follow up on these leads. Thanks again, fellas, for your help.

Danny

Valve Lash adjustment??
DD

I have the same problem with my 74 valiant. I just did a valve lash adjustment and it ran better for a couple of days. now it is back to eating up gas again. A friend told me to check the distributor drive gear because it might be worn.

74valiant:

You and another poster have mentioned valve lash, and I have suspected it all along, although it seems like it should be carb-related.

But: Are the effects of mis-adjusted valve lash typically less evident after full warm-up?? If so, that is another indicator that valve lash is my problem.

You can tune that carburetor all day long, and play with timing, but if the valves are not opening the correct distance the engine will not run properly.

Read the sticky on lash adjustment, and start at ‘step one’ in the tune-up sequence; lash adjustment.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Dannywithadart;

I was getting hesitations when I start from a light. Then I found here that someone was having the same problem, and they say to eliminate a certain vaccum line. I don't remember what it was called, but it did the trick.
basically on the firewall(passenger side) you see 2 fittings with vaccum line, think one goes to charcoal cannister and other to distributor for vaccum advance. I just pulled both vaccum lines from the firewall and the one end on the distributor. the other line, think it went to the charcoal cannister, I plug into the the distributor for vaccum advance. no more hesitation. this may solve your problem.......Jerry