"Idle"-ness is the Devil's Workshop

The Garage Tech Support
1

Last summer my friends and I blew out the radiator (methinks, thermostat temp setting too high) and the transmission (hardened seals) on the way back from Carlisle. Just made it back, though. She seemed to idle and accelerate fine, though – er, as soon as Matthew flipped the carb linkage into the right position, that is.

So off to the transmission shop she went. When I picked Faulkner up, it was idling very choppy – I attributed it to the kickdown linkage or something, and knew that I’d have to get to it as soon as the garage was built.

Well, the garage is built, Faulkner hobbled inside, and now I’m getting to it. First, I pulled the radiator and had the seam resoldered that blew out. I replaced the thermostat with a low temp, and the good news is he’s holding his antifreeze – and the temp seems to be holding low.

Next, I replaced the coil (I had Pertronix ignition installed, but the coil was old) with a Flamethrower 1.5 ohm, as recommended for the V8. I also jumpered out the resistor, as the manufacturer recommends. I also adjusted the tension on the rotor, and cleaned the cap and rotor contacts. Then I started it up.

I had to jack up the idle to keep it running. I pulled each wire in turn – yup, I’m getting spark. Then I put a timing light on it. It seemed to around 10 BTDC (which is the correct setting at idle), but I was running faster than idle – shouldn’t be advanced? So I loosened the lockdown plate on the distributor and turned it a bit, and it seemed to run a bit better; still, when I dropped the idle it was still running rough. A couple of observations:

  1. When I hit the gas, the timing went off the charts, i.e., it must have been around 20 degrees or more. That shouldn’t be happening, should it? Funny, when it’s running fast, it seems to be running fine – i.e., the engine doesn’t balk or misfire.

  2. When I keep the engine as idling as low as I can, I can remove the vacuum advance line – no effect on timing, and I can feel only the slightest of vacuum from the line. (I’m always confused; should vacuum be highest at idle, or lowest?)

At any rate, I’m scratching my head as to next steps. Could carburetor problems be what I’m looking at here? And what do you make of that timing swing?

Dan

2

Hi Dan,
Congrats on repairing the radiator and staying cool, re-cores are expensive!
I am a rusty mechanic, trying to refresh my memory by opening the 57-8 Service Manual.

Vacuum is highest at idle. Carb butterflies are nearly closed at idle, so vacuum at the hose is highest. You should hear and feel the vacuum ifyou pull off the vacuum hose at idle. It should also change the speed of your idling engine.
The correct setting for timing is 10 degrees Before TDC.
When the accelerator is pressed, the vacuum level decreases, allowing a spring in the vacuum advance unit to retard the timing, which delivers the spark sooner.
Foot off the gas, vacuum level increases, advancing the timing back to 10*.
I dunno if 20* of retard is typical/acceptable.
You have an un-original distributor, fitted with Pertronix, correct?
Distributors are designed for specific cars, so maybe you have a compatibility problem..Sure, it physically FITS, but what about the specs?
Your carb still needs an acelerator pump, so if I were you I’d have that kit on hand for Matthew..
Kickdown linkage will not cause rough idle…
I tried to get Pertronix for my car. After two failed attempts, Pertronix admitted they dont have a unit that fits my car (according to my mechanic).
My mechanic Googled “361” and found a company that bought a pallet of early 70s distributors which fit the 361, 383, 400 and modified them with Mopar Electronics. I am taking the gamble and buying one of their remaining stock..if it doesnt work for me, I will send it back.
Dan, take off the distributor cap and try to shake the shaft..any “play” is bad news.
I vote for a carb rebuild first, timing second..
Is yours a 4V? That would be factory issue fpr Sport Fury.
Roger

3

Hi Dan,

Well, a diagnosis from overseas is quite risky, but I totally agree with all that Roger explained. I would also go first for a carburetor rebuild, IF NECESSARY - in any case i would open it and clean the chambers and channels with compressed air. Also check/change the gas filter, if necessary. Then go for timing.

When I hit the gas, the timing went off the charts, i.e., it must have been around 20 degrees or more…

I also observed this on my distributor and I guess that’s ok, but I’m not totally sure now. Sorry I have to look in the shop manual.


Stefan

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Hi Dan & Roger - Dan, I have the later distributor in my 59 Plymouth and my 60 Desoto, they are the same and take the same Petronix Kit #1381A, they are both working great.

Roger - My green 59 has an original dual point distributer. I installed a Petronix Kit #1382 and it also works great.

If you have any questions the Petronix trouble shooter is Marvin at 1-800-827-3758 ext. 1030 Marvin.

Good Luck,
Dick.

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When I pull the power steering hose off, I hear it. But not when I pull the vacuum advance line off. I hardly feel any vacuum at all…

I’ve been corresponding with Ed Eckerson. Ed asked if I was getting black smoke at idle – I am (unburnt gas). He asked me to check if I was dumping gas into the barrels at idle (which would indicate bad needle valves) – I wasn’t. There was the nagging fact, that I was getting “whoosh” from the manifold fitting for the power steering, but not for the vacuum advance…

He suggested I “try” a wrench on the manifold bolts, to test their tightness. D*mn! At least two are loose, maybe more. I remember that the guy who swapped Faulkner’s motor, told me he had to swap the intake manifolds (because of the carburetor? I forget). I guess he didn’t torque it to spec – that’s my next move, to torque it down and see if that doesn’t fix things. Stay tuned…

Dan

Engine running uneasy
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Before I read your last post, my inclination was you have vacuum leaks elsewhere, resulting in almost no vacuum at the vacuum hose.
For sure, tighten the intake manifold bolts, and the carb-to-manifold nuts.
See if you can tighten the carb assembly screws as well.
My car is not here at the moment..so I cannot check, but what does p/s have to do with carb vacuum? I assumed the p/s runs off its pump..perhps you meant to say p/brakes, as in the booster. If that leaks, you will have less vaccum at teh carb and bad brakes…
Matthew, you are needed!

7

Hello Dick,
Thanks for the information.
I didnt know dual point distruibutors were factory stock for Plymouth in '59…
My car presently uses a 361 from a 1961 Windsor…it has whichever distributor was stock for that engine, and Pertronix cannot fit it. I have already tried, twice. Even if they can make something work, I am tired of their attitude…sellling me things that don’t fit ,TWICE now..
I have that other distributor on its way.
One day I hope to rebuild the 1959 “361” block I have stored in my garage, then I will try Pertronix again.

8

Oops – quite right, Roger. I meant to say power brake lines.

Yes, Matthew is sorely needed! But in his absence, I’ve been getting some great help from Ed Eckerson. Ed first had me check the oil, to make sure I hadn’t gotten water into the block from the intake. (Whew!) No signs of it. I then put a torque wrench on the bolts I could, and confirmed that they were all locked down at 30 ft-lbs. The four around the carb, I couldn’t get to (TWSAM was reluctant to pull the carb :astonished: ), so I snugged these up by touch. Three of the 4 were loose; not, terribly loose, but not tight either.

I started Faulkner up again, and it seemed I could run it at a lower idle without it stalling. Still, not running quite right. Ed pointed out that the fact I was getting black smoke at idle – and, quite frankly the strong smell of unburnt gas – meant that I definitely was giving it too much gas at idle. This was confirmed when, on a lark, I pulled the plug out of the manifold where the power brake booster hose was – the engine raced! I was leaning out the mixture the motor wanted.

Ed had me check the idle screws in the front of the block – they were both out 1 3/4 turns. He thought that was too much – and had me turn them both in tandem 1/4 turn at a time. I did that until the stall point, and the engine smoothed out quite a bit. Now when I removed the plug, the engine nearly stalled – I was starving it of gas. So in the end, it seems I had a combination of problems – too much gas at idle, and a manifold vacuum leak. Still, one thing confuses me; more about that next post.

Dan

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Hi Dan, Roger and Dick,

While we are waiting for the next post I’m also confused now. Yesterday evening I went in my garage and checked the vacuum port on the carburetor. First of al, my carburetor is not the stock one but a later aftermarket Carter.

At idle there is almost no suction and when I increase idle the suction becomes stronger. That’s exactly the contrary what Roger said and I confirmed. ?!?!?


Dan – do you have the original carburetor?


Stefan

10

I’m not sure if it’s original, Stefan, or rebuilt once before… How would I know? The carb has AD9 2812S stamped on it, and it’s a Carter AFB.

But I think Roger et. al. must be right. With the carb off, I can clearly see that the vacuum port at the base communicates directly with the intake manifold. And if you remove the power brake hose, you’ll get strong suction at idle, low at higher rpms.

In my case, I think the the pressure is low in the advance line because of air being sucked in around the carb base. I’m guessing that with the volume of air going through the carb at higher rpms, the vacuum drops overall, but tends to increase in the advance line because now the carb is opened up, and its easier for air to enter through the carb throat then around the base.

Don’t really know what I’m talking about; but I do know my gasket is shot.

Perhaps yours is too? Wait until I get the carb back on, and I’ll repeat my experiment!

Dan

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Dan

The number is correct - Your carburetor is the original one.


Let’s see if we can bring a little light into this darkness. The distributor has one mechanical advance (weights and springs inside) and one vacuum advance.

Looking onto the distributor it turns clockwise. When the shaft turns faster the weights are forced outside and turn the rotor cam a little forward (also clockwise) That way the breaker opens a little sooner and delivers an advanced spark. So far, so good.

Your (and my) carburetor now delivers low vacuum at idle (no vacuum advance) and more suction at higher rpm’s. That way the vacuum advance pulls now the breaker plate a little back (counter clockwise) and allows the breaker to open even sooner.

Means the vacuum advance supports the mechanical advance in the same direction. Sounds logical, doesn’t it? If the carburetor would have high vacuum at idle and low at higher rpm’s then the vacuum advance would work against the mechanical and equalize the effect, and that wouldn‘t make sense. Am I right or did I miss something and do I tell nonsense?

Stefan

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I dunno, Stefan. Here’s what the shop manual says about vacuum advance:

“The vacuum advance chamber on the distributor automatically adjusts the spark advance to load conditions. Upon sudden acceleration or wide open throttle operation, manifold vacuum drops, causing the spring in the chamber to retard the ignition timing. As engine load or throttle opening decreases, the vacuum increases and overcomes the pressure spring, advancing the ignition timing.”

So I guess this suggests vacuum advance and mechanical advance counteract each other? I’m mystified!

Dan

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If I recall correctly, I think one way of testing for a gasket leak around a carb is to spray WD 40 around base. If engine races (idle increases) you have a leak. I don’t know if this pertains to what you guys are talking about but I thought I’d throw it out there.

14

its not wd40- it’s carb cleaner. wd40 will not burn. (not that i’ve tried or anything :blush: ) --j

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Reading the shop manual - That makes sense. But it still doesn’t make sens that on advance works against the other

I just talked to a specialist. He confirmed that the vacuum port should have high vacuum at idle and low at higher rpm. He also explained me the following. Manual advance and vacuum advance work in the same direction – they ADVANCE the ignition point, but they work separately. The vacuum advance works at low rpm’s when the manual advance still doesn’t have enough centrifugal force to set out. Later at higher rpm’s the manual advance takes over and the vacuum advance looses suction.

Now we have three possibilities – and no solution. Well, it’s interesting at least. What about some help from a friend? Is anybody here who would go outside and pull the vacuum hose to check when it has high and low vacuum? It just takes two minutes and we would find finally the solution.

Stefan

16

Actually, according to Ed Eckerson, it can be any spray – even water. It’s not combustion you’re looking for, it’s a temporary blockage of the leaking pathway that causes the engine to pick up rpms.

Dan

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I volunteer, Stefan! Now that I have a rebuilt carb and new gaskets. I’ll give it a go…

…after I finish refinishing the front porch (laying down fibermesh and elastomeric paint). Time and the elements take their toll on more than just antique cars…

Dan

18

the shop manual explained it. The mechanical weights RETARD the timing.
The vacuum advance ADVANCES the timing, whichever is required for smooth running. It doesnt take much vacuum to move the points plate.
Start your cars, let them warm up so the idle is down, then pull off the vacuum connection and hear the engine speed change.
Since Dan has Pertronix, I dont know if this applies to his car. Is the Pertronix attached to the original breaker plate, which in turn is moved by the vacuum advance? (I dont mean to get off-topic)

19

Yes, it is – the only thing Pertronix does is eliminate the points. Everything else is the same, including the mechanical and vacuum advance.

Speaking of advance, time for me to “advance” to the kitchen for lunch. The porch is done, now on to Faulkner…

Dan

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Let me tell you about my carburetor rebuilder. He’s the third generation that’s been doing this (Palacio’s – Cuban? Dunno). He’s holed away in a little storefront on North Broad Street in Philadelphia. Got two yappy dogs that guard the counter while he’s in the bad yard tinkering (the back of the store is entirely open to the yard. Charged me $140 to rebuild – painted the entire carb with lacquer, his own special mix of metallic silver and black. Looks gorgeous – like brand new, doesn’t it – but does it work?! I asked about putting anything on the gasket, he suggested a little bearing grease – which I did.

I put it back on the car, warning Marie that I would have to crank it for a while because I needed to get gas into it; and that it may not run right until I adjust it. I turned the key – varoom! It was instantly running!

As before, I had to crank down the idle screws because I was running too rich; I also had to turn down the idle (a bit too much, I’m afraid, I’ll have to nudge that back up). But Faulker was running smooth as silk.

And inexplicably – I’m still getting virtually no suction at idle, Stefan. I’m not sure I’m getting any at higher RPMs, either; and at idle, when I remove the vac advance from the distributor, I get no shift in timing whatsoever. So, I dunno. It’s a mystery to me; but machts nichts – it’s running great now.

So Marie and I took it out for a spin! Ready for my next problem? :imp: :imp: :imp:

Dan

P.S. Palacio’s does a lot of work for shops all over the country; he gets a lot of work from L.A. and Las Vegas, he says. I highly recommend, if anyone’s interested in a carb rebuild. Really friendly guy, fast turnaround, very reasonable prices

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