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

Greetings,

Does anyone know where to find the spec on the correct inches/mercury that this engine should have? I believe the later model years ran between 1-7-21, but mine seems to be around 13-15, is this normal?

Thanks
Gene Wescott

I've not seen manifold vacuum ever listed as a manufacturer's "spec", probably because it's kind of a universal, pretty much the same regardless of make, year, # of cylinders, etc. My '34 gives about 19 inches at idle. Your vacuum is suspect low, look for a leak somewhere. 18-20 inches is a good range for an engine in good internal condition and state of tune.

The attached link is one of the best I have seen about how to detect challenges in the engine as well to tune the engine:classiccarhub.co.uk/articles/tuning-and-fault-finding-using-a-vacuum-gauge.html

By following this guideline to tune the engines, my 1934 1104 is adjusted to 19in,and my two 1929`s are adjusted between 17 and 18in. On one of the 29`I had to add 4deg spark advance to get a higher vacuum, by the same time having the engine to run smooth. A low compression engine should have a lower vacuum.

Since I came across this article I have always tuned the engines on my Packard's together with a vacuum gauge.