Packard Forum Index » V-8 (1955-56)

TRy running spark plugs one heat range colder than the current spark plugs. It won't make up for any lack of distributor fine tuning as JV recommends but a cooler plug can greatly reduce or eleminate spark knock without any other adverse effects unless the plug heat range gets too cold.

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Agree, it is always good science to eliminate the plug itself as the source of ping ignition. In a standard-shift performance car which gets revved up regularly, one heat range colder is standard.

As we've mentioned here and on some other threads, it is not so easy these days to know exactly what plugs are right for a TwinUltramatic Packard.

Today's unleaded gasahol and additives have made all our hard-won plug reading experience obsolete. Just listen carefully and make sure a colder plug doesn't make it go from pinging to missing.

Today's fuel will also "cold-foul" plugs if they aren't running hot enough. I had a customer bring in a car which wouldn't start. The float had stuck and filled the manifold with fuel. After we fixed the float, it still wouldn't start. The plugs were new, looked perfect, would jump a nice spark when tested out of the car. I worked most of a day replacing other ignition components. Finally, I installed new plugs and it ran perfectly. The old plugs looked and tested OK, but they wouldn't hit a lick in the engine under compression. From then on, if I have a missing engine, first thing I do is replace all the plugs with one heat range hotter. If new plugs fix the problem, it is the least expensive part on the car.

jack vines

Thanks everyone for the advice. I have to acknowledge that being a pensioner means the grey matter ain't what it used to be and, as somebody once said, a little bit of knowledge is dangerous and I guess these days I fall into that camp. In any event, I will provide my distributor mechanic with a copy of the service bulletin kindly suggested by HH56 for the advance curve. I'll then follow Jack V's #3 suggestion and monitor the best initial advance by road testing. Actually, my old man was a motor mechanic and he always said to advance the timing until it pings under load, back-off a little and retest, and repeat until it seems right, which I think is essentially Jack's advice. Cheers, John

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JP,

Sounds very familiar. Setting "by ear" is how my dad, also a motor mechanic, and also an owner of 3 V8 Packards, did most of his timing. He also used the timing light, but more as a diagnostic tool as I recall, checking advancing and holding at higher rpm. This, BTW, is a pretty inexpensive check of the integrity of the advance mechanisms, because any "creep" up or down at a steady rpm will be clearly visible.

Initial seat-of-the-pants distributor timing is a good place to start, and very much like your father's method of timing under load: Just advance until the idle gets rough from "skipping," then retard it a touch. A little bit of roughness in the idle can pay off in better road performance and mileage, if you can stand it. Usually helps driveability a bit, too, with less tendency to hesitate on initial acceleration (which is often misdiagnosed as a carb problem, when it's really a timing issue).

Anyway, that's my method, for what it's worth. Family tradition, I guess.

Thanks for bringing up this topic. I am very interested in how your distributor is finally set up and how it performs for you.

An excellent method for timing "by ear" is to continue to advance until a HINT of preignition ping is heard with the engine under heavy load, for example accelerating up a steep hill under modest throttle. Most old-time mechanics considered this the optimum timing and I agree and have used this method for decades on many cars with total satisfaction. The key is, what's a HINT - answer, that you can just barely hear ping and it goes away under either more or less throttle.

If after establishing that, the starter balks a bit on a restart, just back off a hair.

As already noted, you can check the centrifugal advance with the timing light, comparing the advance in degrees with the specifications. For the vacuum advance, if you have a small hand vacuum pump with gauge (an extremely handy tool), you can do the same. Not as easy to do accurately as with a distributer bench-test machine, but good enough to determine that they are working reasonably.

Owen,

Thanks for filling in the on-the-road part of the timing test. Initial timing at idle will not tell you how it's going to go on the road. I would be careful, though, to remember to check whether the mixture is too lean, the plug too hot, or other possible causes of pre-ignition before blaming initial timing. Otherwise, you might wind up with a car that doesn't "ping" under load at speed, but gets lousy mileage below highway speed, hesitates on initial acceleration, and in general runs crappy at lower RPM and cruising conditions, which is really where most of the driving is done. In fact, putting up with a little of the ping-de-ping under rare conditions will probably overall be the best compromise for economy, performance and driveability.

We're also moving into the area of "philosophy" hear, and everyone has their own. Just ask any race mechanic. It gets almost to the point of voodoo and incantations.

But these basics can be very helpful, and especially if there are methods peculiar to the Packard V8 that make certain setups more desirable.

Then, you put in the wildcards-- gasoline quality and "octane", weather (temp, humidity, wind) and our old friend altitude, and you got quite a tricky deal to mess with.

G'day Mates, I can give you an interim update on the "new" distributor, although with not as much detail as I'd hoped. My distributor mechanic has weaved his majic and the car is running much better than before, although the test run was only about 10 miles (a bigger run to come in about a week's time). I gave him the factory specs, including service bulletin 56T-14, and explained that most of my driving is really highway cruising and rarely exceeds 60 mph. The car sits on 235x75 steel belt radials and has a 3.54 diff, which I think calculates out to 2500 - 2600 rpm @ 60 mph. Also, that I had had the vac advance rebuilt and didn't have access to the revised one in the bulletin.

With this info we decided that I was seeking more torque than outright power, so he set the initial advance to commence around 900 rpm and adjusted the weights and springs to ensure a more controlled/progressive advance curve through the rev range. He reckons the factory spec was too conservative. When asked about precisely what the advance curve was he declined to give specific details, basically because he was concerned his 30 years of experience would be given away - he prefers to keep his trade secrets to himself but is more than happy to rebuild any other distributor to these (?) spec's. I suppose I can't blame him for this, even though the info would be going to other Packard enthusiasts mostly in the USA, but that didn't sway him.

Anyway, with the timing set to a smidgen over 10 degrees and powering up a couple of local hills I could not detect any pinging at all and, as I mentioned, I definitely now have a car with more urge than before. As soon as I settle on the new plugs I'll experiment a little more with the timing, but I wouldn't expect to be advancing it much more than it is now - maybe try between 10 and 12 degrees and listen to what happens. The only thing that concerns me doing this is a term I've heard called "silent pinging" and I don't really know anything about this. Any clues will be most welcome. Cheers, John

G'day Fellas, I have now driven a further 120 miles or so, approx 75% highway and the rest on hilly curvy roads. The car is performing very well and to the level I originally was expecting after fitting the Pertronix electronic kit. She pulls strongly and I haven't detected any pinging at all, but have yet to check what impact this has had on mileage. I'm expecting more consistency at least, and hopefully an overall improvement as I seem to be driving with lighter throttle than before. I haven't tried fiddling with the initial advance but will do so in the near future. I set it at 10 degrees BTDC but I'm not sure how accurate the timing marks are and therefore, how much if any I should go beyond. I'll experiment with the advance using the pinging under load method and see where it takes me, but I certainly don't want to overdo it and damage anything. By the way Jack, I told a lie earlier as my spare distributor is a #1110865 - sorry for misleading you. Cheers, John

JP,

Sounds good. Be sure to post the 500 and 1000 mile results. Getting something that works reliably and is proven will help a lot of V8 owners.

Kev, if you're reading this, could some of these proven mods and rebuilds get into in a dedicated thread some day, Kev? With some instructions, parts lists, and pics, they could be very useful.

I think Henry will be pretty much ready quite soon to post a Twin Ultramatic rebuilding guide with photos, just by transferring parts of his Constellation blog.

Just wondering...

It very hard for me to cut up an existing thread to extract only bit of the conversation. But you are welcome to start a new thread and copy and paste the information you want into it.