Drops RPM's in drive/reverse/stop

[moparnation74]

      When the car goes from P/N to drive/reverse he engine looses 300-400rpms from 1000 rpms at idle.  Car was checked for vacuum leaks, timing, plugs, and torque convertor replaced.  Other than that the car responds and performs perfectly.  Running stock ignition and the only thing changed in the distributor was the advance spring.  The carb responds perfectly and was told there was no vacuum leaks present.  As for the motor it is basically stock with a very mild cam over the stock one.  I was told by the mechanic that the motor was built very well and is tight and needs time to loosen up.  Hence that is why I went with a looser convertor which helped a little but not a lot.  So I went back to the stock convertor, it's just a show car not a racer.
       I brought up he idea that the issue may be the advance springs/weights not advancing timing adequately when going into a gear.  However, the moment you touch the gas pedal ever so lightly the timing normalizes and performs perfect.  So I have a restored/bench tested factory distributor coming.  It is just frustrating because at a stop or in gear the engine idles down so much it doesn't sound well. 

I would greatly appreciate any ideas?

[HPP]

Do you have power brakes?

[c00nhunterjoe]

Without knowing all of the details, it still sounds like the converter is too tight.

[moparnation74]

Do you have power brakes?

Manual Brakes, power Steering

[moparnation74]

Without knowing all of the details, it still sounds like the converter is too tight.

The previous convertor was turbo actions 10" 3k+ stall which elicited virtually no change

[HPP]

Do you have power brakes?

Manual Brakes, power Steering

Well, blows my theory.  If you have to have the rpm cranked up to 1000 to get it to idle and it struggles to idle in gear, it can be a leaking power brake booster.

[Cooter]

Normal...barring any off the wall carb, ignition, vacuum adv. Problems....

[John_Kunkel]

Converter often get the blame in these situation but it's usually tuneup related.

Keep in mind that the tightest converter ever installed in a Mopar was coupled to the wildest motor (Max Wedge) and they idled in gear just fine.

[BSB67]

Converter often get the blame in these situation but it's usually tuneup related.

Keep in mind that the tightest converter ever installed in a Mopar was coupled to the wildest motor (Max Wedge) and they idled in gear just fine.

My first guess is tune as well, carb and/or ignition.

To be brutally honest with you, you are relying way too much on your mechanic as well.  As an example, He can tell you NOTHING about the rebuild quality unless the motor comes out and is striped down to its last bolt.  "Tight" has no real meaning

Despite what he said, I would suggest that you convenience yourself that there is no vacuum leak.  Vacuum leak is my second guess.  I wish I had 1 dollar for every time someone would emphatically say they have no vacuum leak, and eventually find one.

My third suggestion is to make sure that the advance springs are not TOO weak allowing some advance in neutral only to have it retard when you put it in gear.

[fy469rtse]

yep vacuum leak , slight one , and will make it hard to find , go through your vacuum doors, reservoir, etc