Carter BBD vacuum port

[ben littleton]

I think i got my valves too tight, i set them at .010 and .018 cold. What would you run them at cold, stock cam?

 

[AJ/FormS]

What I would do;
I would isolate the cylinder to find out which one is missing, by just pulling each wire off, one atta time, with the engine idling.
Then I would swap that sparkplug with either one from any other cylinder, or a new one.
If the miss follows the plug, then throw it away.
but if the miss stays with the same cylinder, then you have a choice; Either swap wires with another cylinder to see if the miss follows the wire; or
do a compression test on that cylinder.
IF
the mixture screws don't seem to do anything, and the throttles are NOT too far up the transfers, (see note-1)
Then you could have one or more of several problems;
1) a plugged or restricted idle circuit,
2) a vacuum leak,
3) the float level is too high

note 1
At 0* timing the engine will likely idle pretty slow, So you just speed it up with the curb-idle screw. If this puts the throttles too high up the transfers, then the engine will idle rich. So then, you will have to reduce the amount of fuel coming from the mixture screws. It may be that any fuel, from the mixture screws could be too much, IDK.
So the cure in the above scenario is to crank in say 5* more timing, so you can reduce the curb-idle speed screw setting, so you can bring the mixture screws back on line.
To figure out if the idle is rich or lean, just take a shoprag, and begin to cover the carburator bores. If the idle speed goes up, then she's getting too much air. If the idle speed goes down, then she wants more air/less fuel.

 

[ben littleton]

What I would do;
I would isolate the cylinder to find out which one is missing by just pulling each wire off, one atta time, with the engine idling.
Then I would swap that sparkplug with either one from any other cylinder, or a new one.
If the miss follows the plug, then throw it away.
but if the miss stays with the same cylinder, then you have a choice; Either swap wires with another cylinder to see if the miss follows the wire; or
do a compression test on that cylinder.
IF
the mixture screws don't seem to do anything, and the throttles are not TOO far up the transfers, see note-1
Then you could have one or more of several problems;
1) a plugged or restricted idle circuit,
2) a vacuum leak,
3) the float level is too high

note 1
At 0* timing the engine will likely idle pretty slow, So you just sped it up with the curb-idle screw. If this put the throttles too high up the transfers, then the engine will idle rich. So then, you will have to reduce the amount of fuel coming from the mixture screws. It may be that any fuel at from the mixture screws could be too much, IDK.
So the cure in the above scenario is to crank in say 5* more timing, so you can reduce the curb-idle speed screw setting, so you can bring the mixture screws back on line.
More coming

Thank you for the reply! Im going thru my valves right now, i set them at .010 and .018 cold. Which was too tight i think

 

[AJ/FormS]

IDK what the spec is but I would start with .013/.023
at whatever the temperature falls to while I am yanking the covers.
Your rocker arms may have ruts hammered into them, by the valve stems, and so if you set your lash with the standard width feeler gauges, they will straddle the rut and give false, wider gap readings. Slantys are well-known for this; 273s not so much.
I bought a set of narrow feelers just for Mopar rockers.

 

[ben littleton]

Ok I've got the timing at 0, strong 20" vacuum at idle, passenger side idle screw is 2 turns out and driver side is 2.5. i still have a miss in the left bank, and the curb idle screw is backed all the way out. Its idling at an acceptable speed, but i couldn't get it to idle any slower if i wanted to. Also, i tried covering up the venturi, and it made very little difference, i had it almost completely covered! Does this point to a massive air leak somewhere, or would that weaken my strong vacuum signal enough to be obvious?

 

[ben littleton]

I found the issue, massive intake leak on the left bank! I checked for one last week and it wasnt presenting. Today i drove it and the miss was even worse on the left bank, and i popped the hood and found fuel around the ports, it was bubbling it eas leaking so bad! So glad its something simple