Packard Forum Index » V-8 (1955-56)

Something just doesn't compute. Maybe there are other Shop Manuals, but the one I have shows only one specification for:
Cranking compression-120 lbs/sq in. min. at 150 rpm
I mean, that's a really lame flathead number. For a 374", I'd expect to see something around 185#.

Since the Packard V8 was built in 320", 352" and 374" displacements, with compression ratios of 7.5, 8.5, 9.5 and 10:1, as well as different camshaft durations in '55 and '56, there should be equivalent different cranking compressions.

Anyone have different cranking compression specifications? If so, please reference which Shop Manuals or other publications.

jack vines

1955 Clippers 150 lbs.
1955 Packard 150 lbs.
1956 Clipper 160 lbs.
1956 Packard 170 lbs.

1957 Chilton Repair Manual

John

Hi, John,

Thanks for that info from Chilton. Those numbers are more in line with my experience.

I should have noted my Shop Manual is the 1956 Studebaker, having a section on the '56 352" 275hp and 9.5 compression. Knowing 120 PSI is way low, I wondered if any Packard Shop Manuals had other data.

Wonder if the 120 PSI is somehow from the '55 Hash engines, as IIRC, they are the lowest compression of all the Packard V8s.

jack vines

There is a calculation for compression reading.

A QUIK rule of thumb is CR x ATM.

1 ATM = APPROXIMATELY 15 psi (that is atmosphereic pressure) times the CR.

So the 7.5 x 15 = 112 psi compression..

8.5 x 15 = 127 psi compression.

NOTE that there is somekind of a fudge factor or other relatively minor factor added to the equation for CR > 12:1.
Maybe google it if u really need extremely accurate calculation.

Packard did have low-compression engine option specifically for export models.