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

The changeover from the higher ZDDP (zinc diallyldithiophosphate?) to the lower levels can be determined by the API code on the container, CI-4 was the last of the high zinc formulations and the reduced level was introduced with CJ-4 to be compatible with catalytic converters required on trucks. But that said, the strong concencus and lots of road experiences say that it's not really a significant factor with the flathead engines and their relatively low cam loadings like your 120 has. Using the older CI-4 or adding zinc additives or boutique oils with higher levels probably falls into the "might help, can't hurt" category. Any good, name-brand oil of proper viscosity should be more than adequate. Probably larger factors to long engine life are starting with a clean oil sump, changing the oil regularly to keep it clean, and regular maintenance of your air filter. Were the car mine, I'd probably be using Shell Rotella T or Mobil Delvac 15-40 unless the car will see lots of cold climate operation.

Another factor to be considered regarding the all-steel roof construction is that of production volume and economics. With lower production volume cars, even as the proper steel and forming technology evolved, it simply wasn't economically possibile to amortize the cost of dies over very limited production volumes until ultimately competitive market pressures forced the issue.

There was a good reason for the soft top in the center of the roof. This was a common feature of all makes of sedans in the early 30s.

The reason was, the steel mills did not make sheet steel wide enough to make a whole roof in one piece. Some expensive cars had steel roofs laboriously welded together from small pieces and the seams filled with lead body solder then hand filed smooth. The Cord 810 sedan had a roof made of seven pieces fitted together this way.But this was too costly and time consuming for a mass produced car.

It was in 1934 that the wide sheets were first made available. General Motors brought out their "turret top" models in 1935 but even then, their cheapest models still had the soft top insert.

The car makers had to invest in giant presses big enough to make a whole roof plus the press tooling, so it wasn't just a matter of buying wider steel. The Cord mentioned above came out in 1936. The Cord company knew they had to have a one piece roof but could not afford the tooling so they were obliged to make the roof the hard way.

The changeover took place between 1935 and 1937, by 1938 I don't think there were any cars with the soft top insert.

I believe 38 Super Eights and Twelves and 39 Twelves still had rubber roof inserts on the closed bodies. See enclosed photo of a 38 Twelve in Russia - photo either from Gusha or perhaps Mr.Ole Book c/o the Nordic Packard Club. 38 Super Eights shared the same bodies, and the 39 Twelves were really just a continuation of the 38 Twelve offerings.

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Hi

How did they piece seven stampings into a metal roof? Have a look!

Steve

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Very revealing, thanks so much for posting those!

Hi Owen

I ran across these Cord pictures on an Ebay listing. I had always wondered how the factory pieced seven stampings together for a solid metal top for such a low volume car.....lots of hand labor!

If anyone has a similar picture of a '41 LeBaron Sport Brougham body showing the leading seams, I'd love to see it.

Steve