Packard Forum Index » V-8 (1955-56)

G'day Mates,

As interest the distributor curve thread seems to be fading and because I'm now enquiring about mileage achieved by others, I thought I'd better start another thread.

But first, time for another update about the distributor saga and I'll preface it by saying we've gone back to the drawing board for some more mod's.

Briefly, after doing a couple of mileage checks, while the old girl pulled smoothly and strongly, she's also using too much juice. First test showed AUS 14.2mpg (US 11.8mpg). After talking to my expert, he suggested testing the vac advance - the reco'd one fitted to the distributor with the Pertronix kit tested out at the factory spec of 16 degrees. The one fitted to the spare distributor tested out at 20 degrees even though both are numbered 1019111 (old age?). Anyway, he suggested swapping them and rechecking mileage, and this improved to AUS 15.5mpg (US 12.9mpg) - still not good enough given that I regularly achieved AUS 19 - 20mpg (US 16 - 17mpg) in the past before the distributor weights started sticking. My driving style is pretty relaxed, with a light right foot and she seems to do best on the highway around 55 - 60mph.

I'd be interested in finding out how this compares with other peoples experiences.

Given these results it was back to the shop with the distributor. I was informed that it had been calibrated somewhere between the factory specs and those detailed in Service Bulletin 56T-14. We are now going to completely ignore that Bulletin and structure a calibration more suited to the car, modern fuel and my preferred driving style. Part of this will be increasing the vac advance closer to 20 degrees as the car was coping fine with that amount with no pinging during the last test. The plan is to get economy at least back to where it was, without any loss of drivability. I'll keep y'all posted on how it works out.
Cheers, John

In 1955 the average for a brand new car was 10.9 mpg American.

I'm not sure how the timing issue affects mileage except that the vacuum advance under light loads should provide more efficiency (ie power) and thus improve gas mileage.
Also, if distributor advance is not enough then the retarded timing will cause low power and rotten mileage, and too much advance will cause low top speed and too high cylinder pressures causing engine damage.

As for how the curves are selected, well I'd have to read a paper on that one. I have seen demonstrations whereby dynamometer horsepower was significantly increased by correcting the advance curve to factory spec. I don't know how that spec. was set for an economy car like the Ford Falcon.

Low compression, broken or missing thermostats, old carburetors, old radiators, and old castings will all inhibit performance and mileage.

For example, years ago I drove a stick shift Carribean that had an NOS 359 block, NOS manifold, NOS carburetor, NOS distributor, etc etc. Boy oh boy that was a brawny automobile and would eat a 53 Chrysler like a snack.

Compression and what not can be good, but old cast iron motor blocks affect things like burn rates and rebuilt carburetors were always a stopgap repair never intended to replicate as new performance.

Hope this helps

Depends on the kind of driving u do. I routinely get 13 to 14 mpg out of my 56 Executive. That's driving Interstate hwy at 70 to 80 mph. Low speed city driving is about 11 mpg. At one time i got as high as 17mpg on a 200 mile trip but i was really trying to get good mileage that time too. Holding a very steady speed.

Gas mileage is more of a carburetor issue than anything else assuming the valve and ignition timing and spark plug heat range and carb heat control is reasonably close to spec.

Contrary to popular belief, the 4bbl carbs will run better mileage at higher engine speeds than at lower speeds even with a 2bbl. Mostly true of any engine.

Check the timing chain. It can be checked thru the fuel pump mounting hole. Requires removal of fuel pump.

14/15 at about 70 with mine. Can't say for sure in the city, but it may be a negative number.....

G'day Mates, thanks for the advice. It seems what I was achieving previously before the distributor mod's wasn't too bad based on your results. The reworked distributor has been refitted and mileage will be retested in a couple of weeks when she goes on another run. I'll keep you posted on what happens. Cheers, John

John,

That other run would be the National Rally would it not? See you there and we can compare mileage figures. Well as much as you can between a '56 Pat and a '41 120.

Hi,


My Clipper drinks as a fish, depending on city or intercity roads it gives 8 to 10 mpg.
Economic... Eh... .


Xavier

Back then gas over here was 22.9-29.9 cents/gallon (approximately 6-8 cents/liter) and maybe a cent or two more for the really good stuff. I guess someone decided anyone affording a Packard could afford that much for gas so mileage was not a big issue.

We mite be more astute to the gas mileage issue if we knoew how the Packard V8 compares to the 55/56 Cadillac V8.

I got 18-21 routinely with my '56 Patrician. Of course I had a 320 in it with HEI and a supercharger, as well as a 600 cfm Edelbrock carb.


And I didn't always drive it at 70 on the highway..