'Bout Studebakers

by Jerry Blount

 The compression ratio of a given engine is the relationship of the cylinder volume when

the piston is at BDC (bottom dead center) - maximum cylinder volume - vs. TDC (top dead

center) -minimum cylinder volume.

The factors that control the volume are:

1) Cylinder bore

              2) Cylinder stroke length

                        3) Combustion chamber volume

          4) Piston head volume

    5) Deck clearance

                          6) Head gasket thickness when compressed

Studebaker V-8 engines typically had compression ratios that were in the range of 7.2:1 to 8.5:1. (Depending on combustion chamber volume, head gasket thickness etc.). 

This allowed use of regular grade gasoline, and provided easy starting and smooth running without overly stressing engine parts.

Many cars of the late 50s had higher compression engines - 10:1 up to 12:1 or so, but this required premium high- octane gasoline. This certainly produced more power, but Studebakers were marketed to be reliable, smooth running, economical cars.

One may notice that Studebaker 259” and 289” engines had the same compression ratio

in spite of the longer stroke of the 289” engine - thus increasing the cylinder volume. For this reason, the 289” engines have “dished” pistons to increase total upper cylinder volume. Then - in 1963 models, Studebaker wanted more horsepower! The Avanti R-1 engine was a 289” but was now fitted with new flat top pistons to increase the compression ratio to 10.25:1. Obviously more power but with the requirement for higher octane premium gasoline.

This gives options when rebuilding a 289” Studebaker. Want more power? Use flat top

pistons! Studebaker never offered such as option but today an aftermarket piston can 

be had in a “1/2 dish” design - with a compression ratio somewhere in the middle of what a full dish vs. a flat top would yield - something like 9:1 to 9.25:1. A little more power without the need for 100% full premium gasoline.