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

Now that we have everyone up to speed on the basics of engine operation lets get back to the rough idle problem:

At this point i don;t even remeber what engine we're talking about. But it doesn;t matter. One possible source of a rough engine idle is carburetor jetting. Not sure if this particular carb has a removeable jet for idle circuit or not but if it does that mite be one source of the rough idle problem.

Since there was some evidence of high speed 'breathing' problem it could also be that any high speed circuit jets of the carb need to be larger.

Some carbs have a certain balance between high speed and idle circuits so changing one could effect the other.

During the mid 70's there was the so called "oil crisis". Many owners changed carb jetting to smaller jets for the purpose of obtaining better gas mileage. Fast forward to the ethanol and other gas additives of today it is quite possible that any economy measures that were taken during the mid 70's could be producing negative engine operation characterists today.

So carb jetting mite be a good place to start after all other diagnosis and repairs have been made.

Owen_Dyneto...

Could you please furnish a source/vendor for the distributor bushings for the Delco-Remy distributor on my 1954 Packard Clipper Super L-8 327ci 165hp. Really appreciate all the good info in this posting!

Max Merritt had a ton of them for different distributors when i got mine for the autolite. I'm sure Kanter, et al have them also.

I've missed a lot while being gone!

I have a baby coming in literally 2-3 weeks, so my time to try your suggestions is thin, but i do read and appreciate them.

Looking at the straight eight wire setup, they're just going to touch. Easy enough to test though, i'll run the coil wire through a small run of rubber heater hose and spread the rest apart with clothes pins. I'll give that idea 1 2% chance of working but since it'll take 10 minutes and no money to test, i'll try it.

Let's address the other ideas:

Timing - damn near perfect but i have to adjust dwell yet so that could change, and is still suspect then

Advances - both distributors ran great in my 288. Engine ran without a hitch. Seems to advance correctly with timing light, not likely.

Point gap and condition - points new but i installed, still suspect

Plugs - all brand new, 2 new sets, triple checked gap.

Ignition wires - brand new set of yellow braided solid core spark plug wires from kanter. If they're bad fred i'll let you know :)

Coil weak - unlikely, umpteen coils later, no issues


Carb linkage adjusted wrong - possible, but for rough idle? I'd think idle mixture wrong more likely? It's idling at the right RPM, not like the idle screw is too low. Just roughly at the right RPM.


low compression - perhaps but you guys weren't feeling that with the numbers i turned in.

MY ADDITIONS:
Choke not opening - starts RIGHT up cold, when engine warmed up choke blade is vertical.

Manifold butterfly stuck closed - actually held with spring so that it's not warming up the intake when car is cold. Parts to fix to factory were missing, don't feel it's contributing to the issue and should help if anything.


Restriction in mufler/exhaust system - car ran great before engine swap at damn good speed, and i have a small exhaust leak at muffler but doubt it's contributing.

Air cleaner dirty/restricted - just remaned. Clean as a whistle and free flowing and pretty.

Not to keep two threads going (with the removing hot spot), i'll report back here and not there:

I'm going to install new bushings in both distributors.

I'm going to quadruple check point gap, and then dwell, and then timing.

If that doesn't fix, i'll try spreading the wires and protecting coil wire just to try it.

I'll check to make sure advance is working again.

If that doesn't fix it i'll stop working until after the 4 bbl is on it and start focusing on fuel/mixture/adjustments to see where that gets me.

Re carb:

"One possible source of a rough engine idle is carburetor jetting. Not sure if this particular carb has a removeable jet for idle circuit or not but if it does that mite be one source of the rough idle problem.

Since there was some evidence of high speed 'breathing' problem it could also be that any high speed circuit jets of the carb need to be larger."

Yes BUT the 288 and 327 are so close that, on the idle circuit, they should be using the same settings and running smooth at a warm sitting idle.

The high speed breathing is likely, however, because i'm using a 288 jetted carb and 288 intake manifold for the moment. If jetting or the carb is the issue, the 4bbl wcfb will likely solve it.

Just curious. When the engine is hot and you try to start it, does it spin as fast as when the engine is cold? Do any of the wires feel abnormally warm?

Yes, rolls over the same speed. Someone who had the car before me had a welding shop make up battery cables for it, and it's never been slow to roll over. Charging system seems good, just had the regulator checked and adjusted and generator totally rebuild by a local shop. if i let it sit for about 45 min or so, i can come out, pump it 4-5 times, then try to start it and it will fire right up as if it was the first thing in the morning and it's cool as a cucumber.

As fred mentioned in the other thread, it may not be the heat that's the issue but that the carb is not providing the right mixture when it's hot. Something to think about as it idles great cold but starts to roughen up when taken off the fast idle and it's warmed up.

Also, its not boiling over and shows no signs of overheating, needle in the middle (although it creeps a bit after sitting after a long drive, but i've always seen that in older cars when the block just keeps heating the coolant after it's shut off.)

When you finish the drive and pull in, and i measure the temp with the IR thermometer, it backs up the dash gauge, usually anywhere from 180-200ish on a softplug or head bolt or something. I don't think the car is really too hot, it's just bringing out the symptoms of whatever is really causing it.

If that engine has ignition timing on a rubber dampened front pulley then check the timing marks for accuracy. Possible that the rubber has shifted causing the marks to be off.

QUOTE:

"Yes BUT the 288 and 327 are so close that, on the idle circuit, they should be using the same settings and running smooth at a warm sitting idle".

NEarly 40 cubic inches difference beween 288 and 327. That's a LOT!!! I would expect significant carb jetting changes for idle AND hi speed regardless of 2 bbl or 4bbl or any kind of carb, idle circuit or hi speed cicuit.

40 cubes is alot of difference, especialy between 288 and 327. If it was 400 and 440 maybe not much carb difference.

To check for "leaking" high tension ignition just open the hood outside in the dark, no clothespins needed