Packard Forum Index » Pre-War (1899-1942)

I suspect the program is calculating power-limited speed, when the car is more likely drag limited. The V-rated tires are still good for lower temperature build

The term "redline" is pretty much a post World War II term. It refers to engine speeds high enough to cause valve float interference in overhead valve engines. That is, redline is the zone above which the valves begin smashing into the pistons. So when you are in the redline zone you are at the limit before engine damage will occur. However, those prewar motors don't spin fast enough. For example, if you try to over rev the Caddy V-12/16s the valve silencers slide on the rockers and you lose power. As well, point ignition systems begin to saturate and ignition breaks down.

Now in aeroplanes with superchargers redline zones can also mean those points where engine revs combined with excessive manifold pressures can cause detonation sufficient enough to cause engine explosion. So the first use of redlines was in aviation during World War II.

Technically a flathead motor does not have a redline because side valve engines can't smash the pistons.

David's observation of driving 45-50 mph in those old Packards is absolutely correct. I knew people who patched old babbitt bearings together with glue and drove for years that way because they adhered to 45-50. Old Packards will run many thousands of trouble free miles that way.

When the manufacturer claims 100 bhp at 3600 rpm, that is the peak of the horsepower curve. After that power falls off rather sharply. If the power output is more than sufficient to move the vehicle above that speed then top speed may be at a higher rpm. With cars like the Packard Speedster they increased the gearing to match peak horsepower at the expense of low speed acceleration.

bkazmerQuote:

The computer program figures both road HP and aero/friction drag. Similar to the graph I posted, where the 2 lines intersect is the theoretical top speed. The V-rated tires are for my own peace of mind despite the higher price. If one is cruising all day at 75MPH in 100F+ heat then that will reduce the margin of safety.

On the other hand, there are places in NV where you can drive as fast as the car will go -- Vintage Racing events for example, where the 1968 BBC Camaro that won it in 1989 averaged 192MPH and had a peak speed of 220MPH. A Ferrari Testarosa in the same race crashed after an H-Rated tire (130MPH) shredded at 170MPH+. It should have had Z-Rated tires, but the owner was stupid and believed that because Enzo Ferrari put H-Rated tires on it as original equipment then it MUST be OK (his argument). He was busted up good and his wife (copilot) died. A large price to pay for being stupid.

Craig

Thank you all for the lively discussion and for your insightful contributions!

For Tim Cole: Your explanation of redline (and the lack thereof in flathead engines) makes sense to me. This being the case, what would happen (hypothetically), if I were to shift the car into neutral, floor the accelerator and hold it there for an indefinite period? What RPM would it reach at its maximum? (Don't worry, I have no intention of doing this -- just a thought exercise!). Do I risk throwing a rod? Breaking the timing chain? Something else? Is it a low probability or near certainty? I am running Pertronix ignition so perhaps ignition breakdown wouldn't occur?

If there is something that will most likely fail, then there must be a "practical redline" (not in the valves-smashing-into-pistons-sense) but, rather, the maximum sustained RPM at which you can be highly confident no catastrophic engine failure will occur. The consensus from this thread seems to put that number in the 2500-2800RPM range. Do you agree with that?

The prroblem is to determine at what point of load and or rpm and or forces cause PARTS TO BEND OR FLEX OR TWIST etc.

IF a part can be kept from flexing then it will not break.

IT might be possible to run somekind of test on the individual internal moving parts of an engine to determine at what point of load or force that they begin to flex. But it would require some sophisiticaed equipment to test each part.

Let me put it this way:
It might very well be possible to run the old straight 8 flatheads at 100 mph and maybe 3800 rpm all day long for maybe 2 days in a row. BUT if the rods and cranks have been CONTINUOUSLY twisting or flexing then they will break after maybe 200 to 300 miles.

As for valve and ignition point float that is childs play to correct by using heavier springs. But heavier springs can shorten longevvity of the valve train.

Bottom line:
If u can keep it from bending, then u can keep it from breaking.

OR
Let it bend and flex continuously and it will break fast.

So the question is:
At what rpm do the rods and crank etcc begin to bend???

I'm surprised the manufacturer, particularly a high-end one like Packard, hasn't run those tests and used the data and results to inform drivers via the owner's manual.

On one hand, the Packard owner's manual is ridiculously detailed (by today's standard) in discussing things like "piston rod seal renewal" and "pinion shaft bearing preload adjustment" but fails to mention what one would expect is basic information an owner/driver would want to know such as what the ideal shift points are and top speed so as not to bend/flex parts and inflict engine damage?

Good Morning all...I would side with Owen and run in the 40 to 45 mile an hour range for pre-war cars. With our old girls, the engine is only part of the engineering. Packard engineers most likely did not plan on cars running at 50 plus speeds for any length of time. The roads and front ends were just not designed for it.

I have two old machines, a 1931 Model A and she runs quite happily at 40 in normal third gear. She has a Mitchell overdrive designed for her and in 3rd over, she will run 56 at the same engine rpms. Over that speed the whole car is not happy. There are many written comments that Ford intended 40 or so for continuous driving speed when the cars were built.

Our 1949 Packard 288 with 3 speed, over drive and radial tires will run 60 quite happily in overdrive. In regular 3rd gear, she is happy at 45. I don't think that the Packard engineers intended her to run over 60 for any sustained period of time.

Does anyone know if Packard ever provided information regarding sustained cruising speeds for their machines?

Enjoy your day and your Packard.

Ernie

A good question to ask yourself when you think about what sustained speeds the cars of the 30s were designed for, is what percentage of the nation's roads were paved! And of those (probably less than 50%), what speeds were they consistent with?

I recall reading of two tests that Packard conducted at their Proving Grounds in the 30s; as I recall an Eight with poured bearings was run at full throttle and retired with engine failure at 5000 miles. A few years later after the adoption of thin shell insert bearings the test was repeated; the test ended at 25,000 miles though I don't recall if it was just terminated or the engine failed.

If you can find it, locate the article about the high speed drive to celebrate the opening of the new Pennsylvania Turnpike, mostly Buicks and Packards and quite a few engine failures during the high speed run from end to end. If someone can locate and post that story I'd be interested in reading it again.

I have a friend with a '38 Eight (a/k/a 120) without overdrive, when he does Interstate highways it's happy enough at 60 mph but it may have the more advantageous rear axle gearing; 4.54 standard but 4.36 and 4.70 available in the 120s of that era. My '48 Custom 8 was quite happy at 60-65 without using the overdrive; as I recall it had a 4.09 rear axle (3.92 w/o overdrive).

Another thing to consider when driving these older cars at speeds higher than those typical for its era is that engine isn't the only consideration; brakes, suspension, lights all have limitations. And though uncommon, just plain old metal fatique can rear its head.

My 1947 Super Clipper engine seemed to operate fine in up to about 55 without overdrive and past 70 in overdrive likewise with the 4.10:1 differential. The engine really needed a rebuild also but seemed content at the above mentioned speeds. As recent as the late 1960's many northern Ontario roads were still gravel.