Re: Normal Compression Test Values for 1931 Super 8

Posted by Tim Cole On 2022/5/15 14:38:15

The Packard manual specifies 85 psi through 1931. They raised it to 100 psi in 32.

Rule of thumb doesn't always work. For example, I had a modern car that always had 165-175 psi for 9.9:1 compression and the manual specified 200 and said anything below 180 was a sick engine. I bought the car new and the engine quit at 112,000. I later found out from an engineer that they were using junk rings for the American builds. The Mexican builds were going over 700,000. If only I was in California when I bought it!

Back to rule of thumb: Generally, an engine will lose 3% horsepower for every 1000 feet above sea level. Which always has me thinking about a publicity photo of a Packard 120 seven passenger fully occupied and climbing Pike's Peak. That means the car was only putting out 70 crankshaft horsepower at the summit. That picture has me thinking that all the overhauling in the world will not restore as new performance in old motors.