Re: The Duchess Project: 1940 Super 8 Convertible Sedan

Posted by Joe Santana On 2018/1/16 1:52:11

This would be trivia, unless after rebuilding an engine, it didn't leak.

So int he 20s and 30s, according to the blueprints, head stud threads were rolled, with the flat end of the stud going in first with slightly over-sized threads and the rounded end up. This made the studs fit tight in the block to prevent leaking. The shank on these studs is smaller in diameter than the threads. How do you make that without shaving the unthreaded center section of the shank?

But in 1939, the first 1940-model 356 Super 8 engines were apparently built using cut threads whose shank diameter is equal or greater than the thread diameter. There were leaks.

Then 8 years later (after a few years hiatus due to war), Packard realized that the cut threads leaked, so they return to making studs with rolled threads.

Were the cut threads to save steel because of the oncoming war? Would metal conservation have begun in 1939?

Inquiring minds want to know.