running rough

[BBIGG BLOCK 396]

I would go ahead and do a general tune up,Points,condensor,plugs,cap,wires and then adjust the carb and timing.I just did a 44 mopar and all it that was wrong was a couple plug wires going bad!

Bobby Dodson

[gtaa9]

Before I bought the car all that was done(points,condensor,plugs,cap,rotor).I pulled the vacuum advance hose off and its getting full vacuum to the dist at an idle?I know that its not suppost to have full vacuum at idle only under full throttle.The vacuum hose gos from the dist to the back of the carb on the bottom.The only other place for a vacuum hose to hook up too is on the left front of the carb.I'm standing in front of the car as I'm looking at the motor.Any suggestions?

[Seattle Sam]

[ QUOTE ]
Before I bought the car all that was done(points,condensor,plugs,cap,rotor).I pulled the vacuum advance hose off and its getting full vacuum to the dist at an idle?I know that its not suppost to have full vacuum at idle only under full throttle.The vacuum hose gos from the dist to the back of the carb on the bottom.The only other place for a vacuum hose to hook up too is on the left front of the carb.I'm standing in front of the car as I'm looking at the motor.Any suggestions?

[/ QUOTE ]

You should be hooked up on the ported vacuum (left front of the carb), you don't need all that advance at idle. Be sure to cap off the port you are coming off of. Set your initial timing with the vacuum line off the carb and the vacuum ports on the carb all blocked off. You'll only get vac advance at light throttle settings (such as at cruise). You won't have any vacuum at wide open throttle either (by design).
-Sam

[gtaa9]

Thank you very much for the information.

[moparts]

Most GM vehicles run manifold vac at dist. This lets you set a low base timing for easy starts and then pulls timing up so that engine runs good at idle. This really helps on higher compression engines.

[gtaa9]

When I pull the vacuum hose off the dist end while the engine is running it dies,that is'nt suppost to happen.This tells me that the vacuum hose from the dist to the carb is hook up wrong on the carb end.I have only two vacuum ports on the carb,one in the back of the carb on the bottom and one on the left front.The choke is hook up to the left front port.What gives here?

[moparts]

If you plug the vac. leak when you pull the hose off does it still die? If so you can set dwell with the vac hooked up, then if you have to you can raise base idle to get the car to run good enough with the vac unpluged from the dist. to set the base timing. Then it should be a matter of adjusting the carb after dwell and base timing are set.

[booklearner]

Hi GTAA,

It sounds to me like several things are wrong here. Typically you want the distributor vacuum advance connected to the ported (not "constant" or manifold) vacuum source. Also, typically, the choke pull off is connected to the manifold vacuum source, not the weaker ported source.

So, I think there are three things wrong here.

1. The choke pull off needs to be plumbed into the manifold source at the back of the carb.

2. The dist. vacuum advance needs to be connected to the ported source (front left?) of the carb (NOT the constant vacuum source).

3. The static timing on the distributor needs to be advanced (the distributor moved) becuse the vacuum advance was incorrectly connected to the manifold vacuum (causing the timing to be "right" in a wrong way.) The strong manifold vacuum applied to the vac. advance was causing the timing to be right, but it isn't the correct way to have it set up. It suspect it wasn't like this from the factory.

Once you get all this done, set the "static" timing (with the vac advance disconnected and plugged) to be around 10 degrees (give or take). Then when you connect the vac. advance back up (to the PORTED source), the timing shouldn't change much. Now, as you speed up the RPMs of the motor, the ported vacuum will come up and add more timing with the vacuum advance. As you approach full throttle the ported source will fall off. Remember that fuel burns at a fixed rate, so you only need (or want) so much timing at idle.

The motor would definitly die at idle the way it was setup with the vac. advance connected to the constant (manifold) vacuum. If fact, it makes perfect sense.

I hope this helps and doesn't confuse too much.
-BL