My Buick Centurion can't "stay alive" on red stop
 

Hi friends,
For almost three years various mechanics have tried to help me on this problem which started after I had my 455 engine totally rebuild in 2017.
They have all offered various solutions which had helped for a few months and then I am back to square one.
When the engine get warm (after a few miles) I am no longer able to keep the engine idling when I hold for red light. It gets very quickly so bad that after I move to park and restart the engine, the engine immediately goes out when I move to drive. It will run basically smooth in Park the the second I move the gear shift to drive, it goes out. Only when the engine gets cooler, I am able to drive the car again.
You can imagine that in this state, I am really not able to drive.
1st mechanic (the one who put the engine together again) thought that the gasoline was boiling and suggested that we put a 1/2 inch thick gasket under the carb to get it away from the engine. It actually helped for some months but soon I found myself in the same situation
2nd mechanic spend numerous hours on the engine, exchanges the rotor and other electric parts and it helped also for some months but again I found myself back at square one.
3rd mechanic (he has also a Centurion 1973 455 cab) and he believed that this must be a carburetor issue and we had it cleaned. This did not work and I finally ordered a rebuild from RockAuto. I just got it and installed it just to find that 5 miles down the road I found myself in the same situation in the middle of an intersection and had to wait 4 hours before I could get my car home.
So now, I assume we have found out that it is neither the electrical system, nor the carburetor. I am still having nightmare that it is something "inside" the engine as it was kind of introduced after that rebuild event.
I am not the guy that gives up, but I must admit that it becomes increasingly difficult to keep up hope and I just hope that someone out there might get an idea after having read the above history.
kind regards
Martin

I would suspect we are either losing fuel or spark.
When it quits , has anyone verified which is absent ?
Sound like they are all guessing and throwing parts at it.
If the idle speed is increased, any difference, if so how much?
We should be able to fix this.

Hi Hanky,
None of the mechanics have exchanged anything relating to fuel. The second mechanic changed the rotor and other items relating to the electrical system, spark plugs etc.
Before I purchased the new carb the third mechanic fine tuned the carb several times since he was absolutely sure it was something with the fuel injection and we also moved the idle up and down but this has zero impact on the situation when the car is hot and you hold for read. Only way you can stay alive is by going into park but then going back to drive it will go out.
in the first few miles it will drive like a dream, absolutely no issue, after a few miles the symptoms start at red lights and get get worse and worse during the next miles and that the end you need to let the car sit for a few hours to get cooled off before you can get any further.

From what you have provided, somebody is guessing.

What needs to be done is; on the spot when the problem occurs do the checks for fuel and spark. If they keep playing around there is a good possibility they are adding problems to the initial problem.
There are simple checks that can be done at the time on the spot when the problem appears.
I have some reservations about 3 "mechanics" that can't determine what is going on.
Can you inquire if any of the mechanics verified there was fuel AND spark available at the time the problem appears? There isn't very much inside the engine itself that will correct itself after a cool down. Either we have those two requirements or we don't, it is that simple.Depending on which is not there determines where we go.

When a carburetor is replaced the only fine tuning that is required is done to perfect cold operation . If the carb was rebuilt properly the adjustments must be done in the proper sequence. So far 4 people have had their hands in there and from what you tell us I have my doubts about whether they know what they are doing.

hi, Hanky,
I will talk to my current mechanic.
I must admit that I am often concerned that the car takes long time to fire up when cold, like it is not getting any gas. However, once it starts it drives very nice for the first few miles. So not sure if problem rest with the gas pump. I understand that I need to get the mechanic to work and check once we have he issue at hand. However, still can't understand how engine can go so smooth in park vs it stops immediately once it goes into drive. For me it should prove that gas is flowing normally to the carb.
let me see what the mechanic says. Thanks for your comments