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

As a lot of you know because you've helped with it, i'm still working the last of the bugs out of the 53 327 i put in my 50.

The car runs at 95%, but the main issue i'm having is a) the car running out of breath around 70mph. (real mph, like 80 on the dash but gps says 5-7mph less) I have a correct 4bbl carb on the way for this motor now, as i have the 50 288 manifold and professionally rebuild carb on there now. I think that might solve that issue.

Secondly, the car, only after warming up and settling down off of fast idle, idles roughly. Shakes a bit, and i don't trust it at stop lights so i put it in nuetral and give it a little gas. It's not that it would always stall, maybe 2 out of 10 times, but it's so quiet i can't hear if it's running with all the traffic noise around me, and once good and warm it can be hard to start again. It takes the fun out of the car.

So far, i've had the carb totally done, new intake/exhaust gaskets, new carb spacer and gaskets, and chased down vacuum leaks and found nothing. Adjusting in the idle mixture screws will get it to stall, and i've adjusted them to where i get the most vacuum like owen_dyneto has mentioned. The vacuum gauge is usually at a steady 17-19 if i recall, with no bouncing or anything to make me suspect any kind of valve issues. (I was following a trouble shooting guide and specifically paid attention to looking for valve symptoms.)

I've rebuilt the distributor. I have 2 distributors and both give the same rough idle. Timing doesn't seem to help it at all and i'm starting to think it's not ignition. I have an NOS WGD carb for an olds 88 and it gives the same rough idle, though a little worse. But it's not a rebuilt carb.

The 288 and the 327 are very close, and at idle the WGD should have no problem smooth idling this motor. With that said, if it is carb related, when i put the 4bbl carb and manifold on it would likely solve it. I'm collecting ideas now for the day soon that i do that swap, and the issue persists.

I did some compression tests today, and this is what i got. Problem is, i have no idea if these numbers are good. After searching, it's hard to find any numbers on here. Packard manual said that lowest shouldn't deviate 10% from the others average, and that doesn't seem to be the case here. Engine doesn't smoke, and plugs look pretty good. If you give the car any gas it smooths right out and generally drives well.

Today i pulled the car out, patted it on the fender and called it a good girl, and fired it up to let it warm up so the choke would be open. Then i shut the key off, and pulled the plugs one by one and did the compression test with the throttle wide open. After every plug i put it back in, so the each cylinder was tested with 7 other spark plugs giving the motor resistance to rolling it over. Maybe that was the wrong way? Anyway, here are the results in psi:


1: 90
2: 95
3: 100
4: 80
5: 100
6: 90
7: 80-85 (can't read my handwriting)
8: 100


I have good oil pressure (30 at idle, 20-25 at idle when really warmed up and cooking) and no knocking, so i hate to do a total rebuild if it doesn't need it. If i have to, it will be done likely in the winter, and i'll have to find a shop to do it.

If compression is good, then i'll keep focusing on ignition, fuel, and timing. If it needs re-ringed or a valve job, then i'll have to wait and have it done over the winter and limp through the season with it like it is now.

Atmospheric pressure is about 15 psi, 8:1 comprssion would yield 120 lbs approx. Although your compression is a bit low it does not vary enough in my opinion to cause rough running. You seem to have rounded up all the ususal suspects but there are more things to check.

The distributor has been switched and the plugs are clean, but that does not rule out an arc jumping on the inside of the cap or plug wires either arcing to ground or to each other. All of those would give the symptoms you are experiencing.

LOw compression would compromise engine power.

Look again at a manual for other ideas.

Good luck

Your compression test readings look reasonable and I would think they are not cause of the rough idle. The preferred way to do a compression check is as you have done, but with all the spark plugs removed. You might try the test again. I suspect you may get slightly higher readings, due to increased cranking speed, but the percent difference relationship will probably stay the same.

Have you checked the distributor rotor, cap, and wires? What do the spark plugs look like and what is their gap? This sounds to me more like an ignition problem. The old time sequence for tuning a motor was compression, ignition, and fuel system in that order. I recommend you look at your ignition system again. Good luck and let us know what you find.

(o{I}o)

Can't remember all you've gone through but here's a couple points that attract interest:

There's no way the old girl should run out of breath at 70. 90, OK, but not 70. That makes me think that either the throttle is not opening the whole way--have someone press it while you look--or your ignition is breaking down. I recall you have nailed all your fuel delivery problems?? It does take a bucketful at highway speeds.

Most every S-8 distributor I see needs new bushings. The shaft is rolling around like an umbrella in an umbrella stand as no one has been twisting the grease cup on a regular basis. The dwell varies all over the place and can cause both problems you are experiencing. Oh, for happy high speed work you also need to be sure both the vacuum and cenrtifugal advances are working which can be given a rough check easily with a timing light: Rev her up to 2000 or so. The timing mark should move, oh two inches or so. At the instant you close the throttle the mark should jump back about halfway showing that the vac advance is working, then creep back as the engine returns to idle showing the centrifugal is working.

Maybe you just need to speed up the idle a hair. Your compression readings are not grievous.

Based on repairs outlined in post 1 above:

Valve lash too tite or very loose and worn timing chain or loose motor mounts come to mind.

Not that it matters at this point but compression checks should be done with ALL spark plugs removed.

How do the sparking plugs look???? Are they sooty or brownish or greyish????

What is the rear axle ratio?????? If it is in the 4.00 range then that could be why it's running out breath at 70 mph.

Float level in carb mite be way too low.

Dear Cortcomp:

Let's see. Is the exhaust smooth or does it feel like random misfires? Random misfires are probably due to vacuum or idle circuit problems.

The compression figures you show are not catastrophic but they aren't great either. I've looked at Packards with uneven compression and poor idle quality that are acceptable on the road because the motor doesn't have enough power to shake the car. If you are lucky your motor might benefit from running decarbonizers through the fuel system.

Disconnect and plug all vacuum lines. Another culprit is the choke pull off.

Another test you can do is called a running compression. In this test you test each cylinder with the motor running.
Such a test will detect broken and stuck rings that cause problems at idle.

The ignition should be showing a good hot steady 20-25KV using a KD tester from NAPA.

After that I don't think it is reasonable to expect proper idle unless the OEM fuel system is being used.

I was looking at an 18th series car with a good Stromberg on it and, after servicing, it ran perfectly. Just like the book and as if it had computer control. I don't run into carburetors that good very often, but when they were new they were really good.

Good luck.

Based on the compression figures and given your pursuit for a dead-smooth idle, a valve grind might well be on your horizon. Not that you couldn't enjoy a lot of miles of driving with them as they are.

As to running out of breath at 70, Ross's comment is a likely candidate. Distributors seem to suffer from complete neglect when it comes to lubrication. If you need bushings or advice, let us know. And I really doubt the rear axle ratio has anything to do with the matter. Even with a 4.69 rear the old prewar tanks managed to hit the mid-to-high 80s or better (true mph).

Thanks for all the replies

By a smooth idle, i mean decently smooth. not shaking the hood while it's up idling, or about to stall. It can slightly surge some.

My fuel delivery seems great, 3-4 psi at all time. If it's fuel related, i really feel it must be carb/manifold related.

I could go open it up today and see, especially now that i have radials i'd feel better. It may have hit 80-85 one of the times i didn't have the gps with me. I just recall it being a little quicker with the old 288 in it, and having more top end. Might be just me. And again, the 288 had the right intake manifold for it, i know that slightly smaller runners would affect top end. I'm not as worried about that issue. I can do 75 or so, but it feels like i'm burying the throttle full bore. I recall 70 being a comfortable 3/4ish throttle with the 288. Not lazily cruising, but not trying for WOT either.

Anyway, let's go through the posts and answer questions:

The exhaust feels like random misfires, it really kind of misses and will smooth out for a sec and miss. When the car is cold on choke and the fast idle is on, smooth as can be.

Have tried blocking the vacuum lines but the carb one, i can try that. Again, it's all been gone through by someone who does fantastic carb work, several multi carb setups headed for barrett-jackson, mecum, etc and has done good work for other local Packard owners, pre and post war. I'd assume that a wgd would be a walk in the park for him and he'd be able to spot a leak in one right off. He's said everything looks good. Doesn't mean it for sure is, but i'd like to have some kind of info pointing to the carb before i take it back again.

Car has oem fuel system, reman MM fuel pump, good lines, new filter, new fittings, etc. etc. I could drive the car all day long if a) i don't plan to restart it for about half an hour or so after shutting it off and b) i don't want to let it idle. I don't suspect any fuel delivery issues. Verified float setting and it was good, and had carb guy double check it when i took it back to find a small crack weeping fuel in the carb body. He said it was good also.

I DO have a small exhaust leak at the manifold, but as i'm switching manifolds i'm going to wait util then to address it. It idled the exact same before i touched the gaskets and i had no intake or exhaust leaks.

Motor mounts are new, and timing chain is new. It's a hydraulic lifter motor and i hear no clack or anything, but i haven't actually done anything with the valve-train.

Cent and vacuum advance are both working in both distributors, but i have no way to verify they're working right, other than that they ran fine in the 288. (I have one delco and 2 autolite dist. one delco and one autolite tested and ran fine. the other delco came with the 327. I am sticking to using the 2 autolites for testing purposes, so i don't have to swap the cap when i swap dist. And the delco is grimy as all hell.)

I do have 2 new bushings for the autolites, but i can't figure out how get at it! It looks like i'd have to grind off or ruin the pin holding the drive shaft to the rest of the shaft, and i didn't see a replacement pin listed anywhere. I was looking through the manuals but haven't found one yet.

Also, side note, i lost one of the breaker plates after swapping one dist to electronic. If anyone has an autolite IGP dist to sell for parts, let me know. I'd like to have 2 perfectly fine and clean working autolites, one to run and one as a spare for the road that i can hot swap.

System has new coil, solid core wires, new spark plugs, new caps, rotors, condensers, and points. I've put a 6v battery charger on while idling to make sure the system wasn't starving for power and it made no difference. Battery is about 1-1.5 years old, napa, and seems fine. Doesn't leave me anywhere.

I can't speed up the idle even to get it smooth until i get near the fast idle range, which is a bit too high imho.

The plugs are gapped at .025 if i recall correctly, and the outer ring that's inside the plug is black, while the porcellan inner is like a brownish stained color. They read, to me from my motorcycle tuning days, as an ok mixture in an old motor.


I think the culprit may still lie in the ignition system, because i had my fingers in it the most. I'll have to find out how to change these bushings, set the gap again, and then find a dewll meter to fine tune the settings and then see where i'm at. If that doesn't help, then i'll be changing manifolds/carbs anyway, so it may go away with the switch.

Thanks for the ideas and i'll report back!

Re the distributor shaft pin, it may be tapered - just look at the OD on each side. It just drives out, and usually can be reused by driving in again and upset the ends if needed to hold it in place. But if not, the pins are a standard item of commerce and can be sourced thru any good supply outfit like MSC or McMaster. A very basic and simple job to rebush.

Though it refers to an earlier Auto-Lite, you might find this useful:

packardclub.org/forum/viewtopic.php?f=14 ... id=8c5a2b10eb706b660e09aa131d2f1a1b

What are the NUMBERS on the spark plugs and brand????? Are they sooty looking or nice and tan or grey?????

Pull one plug wire ata time while engine is running to see if problem is isolated to one or two cylinders.