Packard Forum Index » Post-War (1946-54)

Hello all,

I have a 1949 Packard with a 327. I recently rebuilt the carb and now after it warms up, it idles really rough (to the point of quitting). When driving, it seems to run fine. It is just at idle after warming up. I have adjusted the low idle jets with a vacuum gauge attached and I think it should be close there. I was wondering if it could be the metering rods. Unfortunately, I did not mark where those were originally set when I took it apart. Any suggestions would be greatly appreciated. Thanks.

Also, the carb is a Carter WGD.

I rather doubt that the problem at idle could be the metering rod adjustment as they don't come into play at idle but rather adjust the opening (fuel flow) in the main jets based on demand after the throttle plate is open. If the procedure for adjusting the metering rods isn't given in the shop manual, it is given in Motor's Manual and other publications of the day. Remind me, does the WGD have simple mechanical or vacuum-controlled metering rods?

Are you certain both idle jet passages are clear of any obstructions? Might be worth the time to check this first. When you had the vacuum gauge attached, could you stall or nearly stall the engine by closing either idle mixture screw? And as you opened each in turn, did the vacuum rise within the first 2 turns (or so) to 18-20 inches of vacuum and then level out?

A really rudimentary adjustment of the metering rods would give the smallest step of the rod (bottom section) in the main jet orifice at something approximating full or nearly full throttle opening. It is important to set the accelerator pump stroke first as if the pump bottoms out prematurely it prevents further movement of the metering rods.

Thanks very much for taking the time to respond. This is all very good information. I am by no means an expert on carbs. What's the best way to check that the idle passages are clear? Also, I was definitely not getting 18-20 readings on the vacuum. It was more in the 13-14 range. Just to validate. I was hooking the gauge up to the port that's right by the idle jet screws.

Just to validate. I was hooking the gauge up to the port that's right by the idle jet screws.

Incorrect - that port if I understand you correctly is for the distributor vacuum advance and may be partially (or fully) blocked when the throttle plates are closed. You need to take the vacuum directly on the intake manifold. If there isn't a service plug somewhere (usually is) you can take it by disconnecting the intake to vacuum booster (fuel pump) line and attaching the gauge to the manifold there.

Try readjusting your idle mixture with the vacuum gauge properly connected. If that doesn't solve it, then consider taking the carb apart and cleaning the idle mixture passages; compressed air aided by a bit of carb cleaner solvent should do it after removing the idle mixture screws - make sure the solvent/air blast emerges at the ports inside the throttle bore. If not, try blowing in the reverse direction.

Thanks for the info. I'll give that a try and see what the readings are.

check your complete vacuum system.
They usually run rough at idle when there's a vac leak.
If it's got the dual fuel/vac pump make sure the vac diaphragm is sound/check.
Could be in the wipers, tubing, or hoses anywhere it's routed.

Thanks for all the great suggestions!