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Spark knock in a 32 Packard ??


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Curious question:

Car is a 1932 Packard 902 Standard Eight. Rebuilt engine -- new bearings, pistons, valves.

 

I thought I had a noisy valve or two or three --- a tappet-like clicking sound ---  so I spent time adjusting all close to spec. 

 I was next working on the ignition and went for a test drive,  and noticed the valve clearance noise was much worse. Not anxious to dive into a hot and running engine again, I wondered if the spark timing might have anything to do with it.  And it did.  I retarded the distributor on the roadside until the clicking noise went away.  The engine was quiet and smooth.  So the clicking noise must have been spark knock and not valve clearance.  Right?

 

So the question is, would modern 10%  ethanol gasoline cause pre-ignition or spark knock when the timing is set to 1932 specs? 

 

Packard offered three heads in 1932 --- low compression, standard and high --- each with different spark advance settings.  (I don't know which I've got) Low compression was 12 degrees, standard 9 and high 4 degrees.  I thought modern gas could accommodate far more spark advance than in 1932, so I tried 15 degrees and heard the loud clicking knock.  Roadside adjustment ended up about zero degrees for a quiet engine.  I just set it to the 4 degree mark.  But I am puzzled. 

 

I could try a few tanks of non-ethanol, but I'd rather hear your comments first. 

Thanks again.  You guys are great.

--Scott

Edited by scott12180
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If it is octane related pre-ignition, running on high test should make it go away.

 

Any hot spots in the combustion chamber can cause it too.

 

As far as how high your compression is now, you can get a rough idea by what the compression readings are when the motor is more broken-in. 5:1 gives about 75 pounds. 7:1 about 115 to 120.....etc. There are charts to get an idea. Otherwise to know more accurately, you need to measure the cylinder volumes with a graduated cylinder and oil.

 

Paul

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11 minutes ago, PFitz said:

As far as how high your compression is now, you can get a rough idea by what the compression readings are when the motor is more broken-in. 5:1 gives about 75 pounds. 7:1 about 120.....etc.

Paul

Can you help me out here Paul. I thought compression pressure of 7:1 meant basically 7 atmospheres = 103 p.s.i. How does it work to be 120 p.s.i.?

 

Scott: is there wear in the distributor points cam or on the points rubbing block(s), affecting the dwell? You (and I) probably set the points without considering the dwell. This could affect the timing?

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That 7:1 is measured compression on an engine that I also measured the actual combustion chamber and swept volumes with a graduated cylinder after raising the compression ratio.   Compression ratios are just that.

 

However, engine compression readings can vary for the same ratios depending alot on camshaft design and secondly, a few other factors such as the starter motor speed being strong or weak when doing the compression test.

 

Plus, that 7:1 engine is using Total Seal's "gapless" ring set, which gives slightly higher compression and vacuum readings once the motor is properly broken-in.

 

Paul 

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Today's cheapest regular is 87 octane, at least it is around here. The best available high test pump gas was 76 octane, maybe, in 1932. In other words today's cheapest regular is higher octane than the best high test of 1932. So I doubt your problem is related to too high compression or too low octane fuel.

 

My guess is you had the spark advanced far enough to launch another Sputnik and didn't know it. Timing marks often get out of whack on old cars. Is there any way you can find TDC on the piston and check? It would be a cinch on a Chrysler product but I don't know about Packards.

 

You could also double check your plug wires and see they are all going to the right cylinder.

Edited by Rusty_OToole (see edit history)
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22 minutes ago, DonMicheletti said:

I would doubt that a '32 Packard would have a compression as high as 7:1. Even late in the 30's compression wasn't  that high for most cars

 

I would doubt it too, since that was on a 30 engine that was originally 5.1:1 compression and then highly modified during a rebuild less than ten years ago to make better use of todays higher octane gasoline to increase engine efficiency. 

 

I only posted the numbers to show that you can get a "rough idea" of compression ratio based on  what the compression readings are. Other engines of that same era will likely vary based on the cam design. 

 

And with Scott's motor, It's not unusual that a newly rebuilt engine will give lower readings which should come up as the rings wear in. Plus, after enough miles to break in, the lower compression older engines, being less efficient, can build up carbon layers in the combustion chamber and the piston top, that then not only helps seal the rings better, it takes up volume in the combustion chamber thus raising the compression ratio above the original measured ratio.

 

Plus, if the cylinders were bored out, and or, new taller pistons installed, and the block and head were milled, those will raise the compression based on how much those changed.

 

Paul   

 

 

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Paul's compression pressures and comments on how it worked spurred me to look further into how it works. It was not as I expected. This paper gives a formula.

Nominal compression pressure.pdf

which is

compression pressure = (pressure at bottom dead centre [usually 1 atmosphere]) * (volumetric efficiency) * (nominal compression ratio)(specific heat ratio of working fluid)

 

where the specific heat ratio of petrol + air, corrected for engine heat, is about 1.3 and

the volumetric efficiency depends on valve timing - if they are open more than 180°, it is about 60%.

 

So for 7:1 nominal CR, the compression pressure at TDC = 14.7 p.s.i. x 0.6 x 71.3 =  6.46 bar = 110.7 p.s.i.

 

The gauge reading will be one atmosphere less than this because the gauge reads zero under air pressure. So the gauge reading will be 96 p.s.i.

 

I have been looking for typical volumetric efficiencies of flat head engines. So far I can't find any.

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I can't find typical volumetric efficiencies (VEs). But I have found MoToR's Auto Repair Manual gives nominal compression ratios and in another table, compression pressures. My manual starts with 1935 models.

 

For the 1935 Packards, standard CI was

  • 6.5 for the 120, 1200, 1201, 1202;
  • 6.30 for the 1203, 1204, 1205; and
  • 6.4 for the 1207 and 1208.

Compression pressures (CP) are given as

  • 105 for the120;
  • 108 for 1200-1-2-3-4-5-7-8 with standard heads.

Higher compression heads were available but the CRs are not listed.

 

So given VE = (CP + 14.7) / (14.7*CR1.3),

  • for the Packard 120 VE = 71%.
  • for the 1203-4-5, VE = 76%
  • and so on.

For the 1940 Buick Special Eight, CR = 6.10, CP = 112 @ Cr. Thus VE = (112 + 14.7) / (14.7 * 6.11.3) =82%.

 

For a 1939 Studebaker Commander, CR = 6.00 and CP = 105 @ Cr. Thus VE = 119.7/(14.7 * 6.01.3) = 79%.

 

Interesting. These numbers seem higher than I would have thought.

 

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Remember compression tests are done with the engine barely turning over. Older engines were optimized for best VE at low to mid range, and ran out of breath at higher speeds. I suspect a modern high perf engine would have a worse VE in a compression test but much better at high RPMs.

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Coming back to Scott`s original question. The octane rating of the gasoline is going to be better than of old, and will not be the problem. I suspect that your trouble is timing related. Firstly, the engine would run, but would not be very happy if the spark was coming at TDC. If that is what you see, then I think you should check to ensure that the timing marks are in the right place. This can be tricky with a side valve, unless it has an unscrewable bung above the piston like my 35 De Soto. With the plugs out, you may be able to observe the piston coming to the top through the plug hole and verify the TDC mark. After that, you can retime in the usual way.

 

Are you using a strobe timing light? I always do. very useful for verifying a spark on each cylinder in turn.

 

Adam.. 

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What I am doing is, with the engine off and cold, removing the starter, setting the pointer in the starter "window" for the degree advance setting recommended, then rotating the not-advanced distributor until the breaker points open.

 

Is this not the correct way to set spark timing? To my knowledge, there are no other timing degree marks except on the flywheel exposed by removing the starter.  

 

Or is this procedure supposed to be done with the engine running using a timing light ?!?  Never occurred to me. 

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I don't think timing lights were invented back then!

 

Could the flywheel or ring gear with the mark be put back in the wrong position so your timing is quite a bit out? i.e. are you sure the marks are correct?

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The SURE way is to remove #1 spark plug and the front valve cover and rotate the engine to the top of the compression stroke, perhaps using a plastic straw angled toward the top of the piston. ensuring that both valves on #1 are closed.  This will be Top Dead Center (TDC) on #1.

 

The above assumes that factory timing instructions call for #1 rather than any other plug; if any other plug/cylinder is specified, use that cylinder.  The rotor should then point exactly at the center of the appropriate plug wire contact for that cylinder.  THEN check your timing marks on the flywheel to see if you're in the very close ballpark; if so, your flywheel is not out of proper registration.

 

Do you have dual points?  If so, there are specialized instructions for synchronizing those two sets, and this is best done with the distributor head in a vise.

 

IF all that checks out, or if you want to try a Q&D (quick and dirty), hook up a vacuum gauge to a warm engine, and at slow ide advance the distributor to maximum vacuum, then retard slightly, say 0.5 inch Hg less than max vacuum.  Road test.

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Hi Scott

 

You are following exactly the correct procedure! I was alluding to the possibility that the timing marks may be incorrectly located, perhaps if the engine has been disassembled at some stage. The reason that I thought that, was the persistent problem that you have. Grimey, two posts above this one, has described the process better than I did. A man who really knows his onions!!

 

It would be worth checking for TDC and confirming that your timing marks on the flywheel are in the correct place, because TDC is not where the engine should run most happily. It really sounds as though the marks are in the wrong place.

 

Adam..  

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Also, I just remembered, many , if not most, Packards of this era have twin contact sets in the distributor. Some need the respective sets of contacts to be synchronized. (I have a 1928 Packard 533, but that has the contacts on a common baseplate, so synchronization is not needed). If yours has separate contacts, there is a process for synchronizing them on the bench, if you need it, but you can get away with setting the ignition timing on the first set on No1 cylinder in the usual way, then rotating the engine one revolution by hand, so that No8 cylinder is at TDC firing, then set the second set of points such that the contacts are just opening at the correct engine position on the flywheel. I hope that this makes sense to you.

 

Apologies if you do not have twin contacts and this is all irrelevant!

 

Adam..

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All your comments and advice is much appreciated !  Thanks very much.  I'll give the vacuum method a try for comparison. . . . when I can find a vacuum gauge.  And check the timing marks.

 

Regarding twin points, this Northeast distributor used to have twin points but at some time someone converted the ignition to a single set of points with a new backing plate.  I don't know the details but the previous owner might if it makes a difference.

 

--Scott

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39 minutes ago, scott12180 said:

but at some time someone converted the ignition to a single set of points with a new backing plate.

(This is based on Pierce experience, where dual-point 8s had distributor cams with half as many lobes as the number of cylinders, with one set of points firing half the cylinders and the second set firing the other half.)  So if your distributor was converted to single points, undoubtedly an 8-lobe distributor cam was installed at the same time, perhaps/probably from a later-1930s Packard 8--for which dwell and point gap adjustment specs are available.  That is, don't use 1932 point gap specs for the single-set conversion.  There may be some trial and error here to get it right.  Look for the earliest Packard 8 in the 30s with single points and try that gap.  My MoToR Manual shows for the 1936-37 320 cid engine (essentially the same as yours except distributor) point gap 0f 0.012-0.018 and cam angle (dwell) of 34 degrees.

 

The wide acceptable range for point gap was based on the fiber rubbing blocks at the time, which wore in and lost about 0.002 of point gap in the first thousand miles.  With used but serviceable points (or new modern points with nylon rubbing blocks), I'd try 0.015 or 0.016.  Thankfully, we have dwell specs for the 320 cid engine.  DWELL (cam angle) is what makes the engine run well, and point gap is merely a mechanical expression of that but assumes there is not major wear on the cam lobes.

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Afterthought:  Unless your dwell meter can be set for either 6 volts or 12 volts, it's probably a 12V-only meter, in which case you must power it from a 12V battery.  I keep a couple of very small, sealed 12V batteries such as used for gate openers and home security system backup power for this purpose.  I also use them to power GPS units for touring in 6V cars.

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Thanks for the advice on dwell. 

I'm going to appear very ignorant here because it's late and I don't want to spend the next hour searching Google. . . .

Could someone explain the importance of the dwell angle? Or just give me a tutorial on dwell from basics?

To me, it seems that dwell is determined by the points gap.  Larger gap, smaller dwell.  Dwell governs the amount of time for the ignition coil to "charge" before the points open and the spark is thrown. 

But as long as the points gap is reasonable, how else do you set dwell and why is it important?

 

--- A bear of very little brain with a Classic Packard.

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37 minutes ago, scott12180 said:

To me, it seems that dwell is determined by the points gap.  Larger gap, smaller dwell.  Dwell governs the amount of time for the ignition coil to "charge" before the points open and the spark is thrown. 

But as long as the points gap is reasonable, how else do you set dwell and why is it important?

You've got it, Scott.  Some cars in the early 30s used two coils and two sets of points that would fire alternately from a distributor cam that had half as many lobes as the car had cylinders.  That allowed each coil longer time to "saturate" or re-charge before it had to fire again.  That was necessary due to coil technology / capability at the time, AND higher speed (rpm) engines, generally with 3200-3400 rpm max horsepower ratings--vs., for example the slow turning Pierce dual valve engines with 2500 rpm redlines.

 

When I was very young, I had a 1950 Pontiac 6 with 90k miles which called for about 0.021 point gap.  It ran like crap with new points at that setting, because the dwell was way off from spec.  To get the specified dwell, I had to reduce the point gap to 0.014--by trial and error--at which point the car ran beautifully.  The problem was that the dist cam was substantially worn--previous owners must not have believed in cam lube when installing points, or perhaps the cam escaped the hardening process.

 

The correct dwell, if you have it in specs (not likely for many 1932 cars), is what assures that the car runs well.  The specified point gap will get you the desired dwell or close to it **IF** your cam is not unduly worn.  Use a specified point gap first because it's easier than attempting many different settings, then check dwell to validate that point setting as appropriate to the specific distributor after 85 years of wear.

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I have just had a thought !

 

If your distributor has undergone a conversion to an 8 lobe cam and a single set of points, then the distributor will certainly have been out and may have been put back 'one tooth out'. Definitely set the dwell as Grimey has described. That is all important. Then it would be a good idea to set the ignition advance either statically, with an ohms meter, or by ear. You will be unable to start the engine with the starter removed to view the timing marks!

 

All very interesting.

Adam..  

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1 hour ago, Alfa said:

If your distributor has undergone a conversion to an 8 lobe cam and a single set of points, then the distributor will certainly have been out and may have been put back 'one tooth out'. Definitely set the dwell as Grimey has described. That is all important. Then it would be a good idea to set the ignition advance either statically, with an ohms meter, or by ear. You will be unable to start the engine with the starter removed to view the timing marks!

YES!  Alfa/Adam, we may think alike because my late father was a Brit :-)

 

The first test I recommended (at TDC on the appropriate cylinder, where is the rotor pointing?) will tell you whether the dist may be one tooth off.  At TDC, adjust the dist, even changing position by one tooth, to get the rotor pointing at the appropriate terminal in the cap.  These cars have little if any initial advance, so Alfa's recommendation for static timing makes sense.  Once you have the dwell right, THEN you can "power time" by using the vacuum method.

 

On my 1930 Pierce (two coils, two points, 4-lobe dist cam) and my 1934 and 1936 P-A 8s (same except for single coil), I set the initial advance fast (advanced beyond recommended setting) and use the spark control in the cab to fully retard for starting and for prolonged slow idle (necessary to smooth the idle out).  That is to get more advance at speed, since all have only mechanical advance and no vacuum advance.  

 

Scott, please keep us posted.

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Apologies for not replying sooner.  Life gets in the way sometimes. . . .

 

I checked the dwell on the 902 and found that I had about 28 degrees with a points gap of 0.018".  I adjusted the dwell so that I now have 33 degrees, (Grimy recommended 34 degrees)  and the points gap falls in at 0.012" ---  quite a difference in gap. 

 

I also set the advance to 4 degrees on the flywheel, which corresponds to the "high compression head" setting in the specs.  Tomorrow I'll go for a long ride and see what happens. I can always adjust spark timing on the road.

 

As for the distributor at TDC, I did not dive into that yet but as I recall from the rebuild on this and my 236 (long ago) you can't be off a tooth on the distributor drive, nor even 180 degrees --- there is only one way it can mount.  Unless there's a "toothed drive gear" deep inside the engine, like driving the oil pump.  So nothing I can easily change.  (I could be wrong, of course).  Also haven't yet determined that Number One is at TDC.  That will take some gymnastics.

 

I am not being a good scientist because I'll be changing two variables --- I cleaned out the gas tank recently and wanted to see how the car runs on non-ethanol.  So I'll have the new dwell and non-ethanol.   I'll report back how it goes.

 

--Scott

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Hi Scott,

 

Congratulations!  If I understand you correctly 28* initial advance will certainly account for your spark knock!  I'll bet it was a bear to start, too!

 

Glad you have the one-way-only slot on the distributor head--as do Pierce 8s and 12s.

 

Dwell:  30* or above should work well, but it will necessarily be trial-and-error, as we don't know specifically what engine the 8-lobe distributor cam and the points are from.  The later 320 engines were my best guess.  **Perhaps** you may have some worn cam lobes to account for the narrow gap to get 33* dwell.  

 

For me, the next step would be to do the advance to max vacuum, then back off 0.5 to 1.0 inch of Hg.  On my cars, I put excess initial advance but the tradeoff is that I must manually retard the spark (on the steering wheel on the '30, dash knob on the '34 and '36) for starting.

 

I'm anxiously awaiting the results of your road test.

 

VBR, George

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I did not have the spark advance set at 28 degrees, but the dwell angle was 28 degrees when I first measured it.

 

Anyway, with the new dwell set at 33 degrees and the points gap at a corresponding 0.012", the road test was quite a failure.  The engine sounded like the anvil chorus with the knocking/pinging so bad that after three or four miles I had to pull over and retard the spark by rotating the distributor.  I finally found a maximum advance with no pinging and continued on. 

 

At my destination before I began the 35 mile trip home, I thought that the engine had not seemed "well" after retarding the spark.  Out of curiosity, I reset the points gap to 0.019" (with a corresponding dwell much less), and the car seemed to run much better.  Slight pinging. Once home, that 0.019" points gap measured to be 4 degrees advance on the flywheel. 

 

So I noticed really nothing at all regarding dwell.  The engine felt better with a large points gap (smaller dwell) and 4 degrees advance than a small points gap (33 degree dwell) with the same 4 degrees advance.

 

Now I'm wondering about carburation.  The car has a large Zenith carburetor which I don't know much about but will ask my questions under a new thread.

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Scott, I'm really sorry you're having so much grief with this.  May I suggest that you sort out the ignition before proceeding to the carburetion.  Get rid of the ping first.

 

Changes to the dwell / points gap affects the timing.  I had *guessed* that the previous owner who converted to single points had used points and an 8-lobe cam from a later 320 cid engine; that's what most of us would have tried first.  Sounds like that was not the case.  Absent any information in a logbook or other records, that leaves you to figure out what point gap to use--and indeed which point set to order when it's time to replace yours.  A comment by Tinindian in a recent thread addressed some substitutions he had made over 500k miles in his slightly older Pontiac, but that such modifications were noted in a logbook for future owners.  This is an object lesson to us all--when we mess with factory equipment or adjustment specifications, we'd better make notes of what we changed and their part numbers, and what deviations from factory specs we used to get good performance. Variations among different points include the height of the rubbing block and the arrangement/position of the base of the points set.

 

Given your experience yesterday, I'd try this:  First. "start from scratch," meaning that you temporarily put aside factory specs and find What Works.  Vacuum-time the car at your on-road point gap reset of 0.019 and road test.  Since it was pinging at 4* advance, you will probably need to retard the spark.  I trust that your in-cab spark control was at full advance during (1) the pinging on the road and (2) while checking your initial advance when you got home.  During your road tests, try adjusting the in-cab spark control:  if it's pinging, retard the spark; if it's NOT pinging, try advancing until pinging begins under load conditions (hills or strong acceleration), then back off in the retard direction.  This will largely be trial and error.

 

Then try setting the points at, say 0.021, and vacuum-time again.  It will be either better or worse.  If better, try 0.023 and vacuum-time again; if worse, reduce point gap and vacuum-time.  It's important to vacuum-time with each adjustment to eliminate that variable.

 

Addressing previous owners' or mechanics' screwups, especially undocumented ones, is a pain.

 

As for matching your points for future replacement purposes, if you have them out photocopy them for actual size, and photograph them as well.  Compare to drawings in ignition catalogs, such as the VERY useful AEA (Automotive Electrc Ass'n) catalogs, and older Filko, Standard, or Echlin ignition catalogs.

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IGNITION TIMING ON PRE-WAR PACKARDS

 

It is certainly very nice that so many people want to try and help, (and see themselves as posters).    Fortunately,  many are honest in admitting they know little about Packards,  so their benefit to your problem may be minimal.

 

There is nothing mysterious or "different" - no need for exotic experiments, to properly "time" the ignition on a pre-war Packard of ANY series.   The only "annoyance" is that up thru the early 1930's,  the timing marks are on the fly-wheel - so you have to remove that big heavy starter to see them.   Timing marks on flywheels were the common method up thru the mid 1930's.

 

Of course you can and SHOULD use a strobe-light to set your spark advance.  While the 'correct' setting as far as the tech-literature of the day calls for 9 BTDC,  you will find you can get better performance by going several degrees more advance.   A good simple way to find how far you can advance,  is when the motor starts indicating it is "kicking back" when starting.  Just at the point when you first feel a "kick-back" will be ideal for both power and economy.,

 

I would be surprised if you could get "pinging" from modern fuel absent really REALLY excessive spark advance.    I hope you are not hearing some kind of mechanical failure, which can be disguised by backing off the spark advance.

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Peter, if you followed this thread, you will note that a previous owner changed to a single-point system in the Northeast distributor from the dual-point.  So far we don't know what plate and points, and 8-lobe distributor cam, are in place now.  That's what Scott has to deal with.  In the absence of you Packard experts jumping in with your extensive knowledge,  I've jumped in with a diagnosis from afar based on my knowledge of other makes, not necessarily Packards.  I will gladly defer to Packard experts.

 

Of course you can see timing marks on flywheels without removing the starters!  You may have to crane your neck a little, which may be difficult when your nose is so far in the air..

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 Not knowing what engine that distributor was meant for, if the centrifugal advance weight springs are the wrong tension for that engine, or they are weak, the advance curve might be coming in to full advance at too low an rpm  and that will sometimes cause pinging.  

 

Retarding the initial timing to correct that can make the engine sluggish. Try stiffer advance weight springs and see if that helps get rid of the ping. If so, then you can go back to original initial advance to gain some low rpm power.

 

BTW, there's more to matching up a carb than having linkage match up and having an adjustable main jet. If the venturi and other internal jets/restrictions are too big the engine will be lethargic. If all that is too small, the engine will be peppy at low rpm, but run out of top rpms. You want a carb from an engine that is very close to the same CID as what your putting it on, or you'll be forever chasing your tail trying to get the engine to run right.   

 

Paul 

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13 minutes ago, Grimy said:

Peter, if you followed this thread, you will note that a previous owner changed to a single-point system in the Northeast distributor from the dual-point.  So far we don't know what plate and points, and 8-lobe distributor cam, are in place now.  That's what Scott has to deal with.  In the absence of you Packard experts jumping in with your extensive knowledge,  I've jumped in with a diagnosis from afar based on my knowledge of other makes, not necessarily Packards.  I will gladly defer to Packard experts.

 

Of course you can see timing marks on flywheels without removing the starters!  You may have to crane your neck a little, which may be difficult when your nose is so far in the air..

 

11 minutes ago, PFitz said:

 Not knowing what engine that distributor was meant for, if the centrifugal advance weight springs are the wrong tension for that engine, or they are weak, the advance curve might be coming in to full advance at too low an rpm  and that will sometimes cause pinging.  

 

Retarding the initial timing to correct that can make the engine sluggish. Try stiffer advance weight springs and see if that helps get rid of the ping. If so, then you can go back to original initial advance to gain some low rpm power.

 

BTW, there's more to matching up a carb than having linkage match up and having an adjustable main jet. If the venturi and other internal jets/restrictions are too big the engine will be lethargic. If all that is too small, the engine will be peppy at low rpm, but run out of top rpms. You want a carb from an engine that is very close to the same CID as what your putting it on, or you'll be forever chasing your tail trying to get the engine to run right.   

 

Paul 

Actually, on Packards of that era you CANNOT see the timing marks without removing the starter.

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2 minutes ago, Restorer32 said:

Actually, on Packards of that era you CANNOT see the timing marks without removing the starter.

I stand corrected.  Thanks for educating me.  What were they thinking?  What is the process for adjusting distributor timing?

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George is right not to start mucking with the carburetor just yet.  What started this, however, was poor fuel economy that made me think about what was what. That's when I began to check everything and discovered the source of the slight pinging was timing.

 

However, SaddleRider suggested that due to the unlikelihood of spark knock in a car like this without huge advance, a mechanical failure could cause pinging, which was exactly what I originally feared.  But what could fail to cause that kind of sound?

 

Paul's comments on distributor advance reminds me of a 1925 Franklin I once owned which, as I try to recall from 30 years ago, ran very rough at road speeds.  I don't recall pinging, just rough running --- lurching, hunting.  Someone at the Franklin Trek (the late and very much missed Don Kitchin) tightened the advance springs on the distributor and the problem was permanently solved. 

 

I wonder. . . .

I will certainly take a look.

 

My only fear is that I do hear pinging at highest rpms, like 50 mph, going up a slight incline.  I would think that with 4.69 gearing at 50 mph it should be fully advanced no matter what. 

 

Again, thanks to all you who are contributing your thoughts.  I very much appreciate being able to bounce ideas around with you guys.  Let's keep the thread going and I'll keep you all posted. 

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Ok, that helps to know when/how it's pining. Pining at 50 mph, while going up an incline, with rear gears that tall, is very unlikely due to too much centrifugal advance,..... unless this distributor has a vacuum advance that's stuck full on ?

 

Paul

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I doubt very much that there's a vacuum advance.  It IS a good idea to check the weight springs.

 

Scott, perhaps a Packard Club technician could help you better.  Can you acquire or borrow a correct Northeast distributor for your 903?  With the semi-Frankenstein mods to that distributor--and we don't know whether the springs and weights were changed, you could play around for days trying different possible solutions.  Running (temporarily) someone's correct backup distributor could tell you (1) whether there is something else wrong and (2) help you get your substitute carb dialed in as best you can.

 

You mentioned fuel mileage:  For comparison, I get 6.0 to 8.5 in my 1930 Pierce with 366 cid and updraft UUR-2 carburetor, running on our mandatory 10% ethanol, and somewhat better (7-10) with the '34 and '36 385 cid--but they have downdraft EE-3 carbs.

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I swapped some advance springs on the distributor today.  What was there seemed very weak ---- one spring wasn't even in tension.   Easy enough check because I can always put the "original" springs back.  Now I've got slightly stiffer advance springs.  I'll road test without changing anything but I am doubtful this alone will solve the problem.

 

Unfortunately I don't know of anyone with a similar car to borrow a correct working distributor.  That would be ideal.

 

I will check as best I can to be sure number one is at top dead center since the flywheel is right now at 4 degrees advance.  Should be pretty darned close but without removing the head or the oil pan, all I can do is insert a bent wire and determine if the piston is nearly flush with the deck.

 

I got something like 9 mpg before I started any of this.  I thought with a  320 cu-in being driven reasonably gently I should be getting 12 mpg or more.  The pinging was annoying but a back burner concern.  Then I began to measure clearances and specs. . . .  Pandora's Box opened.

 

I still think the carburetor is running rich.  Someone posted a service booklet for this Zenith, which apparently is a Marine Carburetor. I'll study that.

Would excess carbon buildup cause spark knock pinging?

 

--Scott

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10 hours ago, scott12180 said:

I swapped some advance springs on the distributor today.  What was there seemed very weak ---- one spring wasn't even in tension.   Easy enough check because I can always put the "original" springs back.  Now I've got slightly stiffer advance springs.  I'll road test without changing anything but I am doubtful this alone will solve the problem.

 

Unfortunately I don't know of anyone with a similar car to borrow a correct working distributor.  That would be ideal.

 

I will check as best I can to be sure number one is at top dead center since the flywheel is right now at 4 degrees advance.  Should be pretty darned close but without removing the head or the oil pan, all I can do is insert a bent wire and determine if the piston is nearly flush with the deck.

 

I got something like 9 mpg before I started any of this.  I thought with a  320 cu-in being driven reasonably gently I should be getting 12 mpg or more.  The pinging was annoying but a back burner concern.  Then I began to measure clearances and specs. . . .  Pandora's Box opened.

 

I still think the carburetor is running rich.  Someone posted a service booklet for this Zenith, which apparently is a Marine Carburetor. I'll study that.

Would excess carbon buildup cause spark knock pinging?

 

--Scott

 

Yes, carbon can cause a hot spot - much like a glow plug - one of the things I mentioned early on. Especially if the carb runs rich on level roads and then goes lean on hills.

 

BTW, if you do have a marine carb, there likely is no power enrichment circuit like a car needs. The lack of such a circuit will make it lean out on hills.  This was a problem with the marine/stationary engine carbs that were showing up as replacements for the potmetal carbs of the late 1920's.  They run ok at idle and on level roads, but with no way to properly enrich the mixture proportional to engine load, such as hill climbing, they go too lean. So, typically, the owner's opened up the main jet to "compromise" for hills and then the carb is running too rich when not under load.    Sound familiar ? 

 

There's a bunch of 28-29 Franklins running around with newer marine/stationary engine Zeniths that were sold as replacements,.... except for one 28 from northern NYS.  I'm working on getting more of the automobile version available for them.

 

Paul

Edited by PFitz (see edit history)
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Spark Knock problem appears to be solved. 

 

I replaced the advance springs on the distributor with some stiffer springs which I had ---  one of the original springs looked so weak that it wasn't even in tension when fully advanced.  That alone made the car run so much better and no pinging. The advance is now set at 9 degrees on the flywheel, exactly what is recommended.

Thanks to Paul "PFitz" for the suggestion and hence reminding me that I had this similar problem 30 years ago on a Franklin.

 

Now to do something about the carburetor.  The engine is running so nicely right now that it's hard to believe that the Zenith marine carburetor is doing harm.  Sort of like how you might feel great when you drink scotch and smoke cigars. 

 

Thanks to everyone who offered a suggestion.  This was a good learning experience.

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