Re: How come Packard didn't make an OHV straight 8?

Posted by PackardV8 On 2008/6/18 23:34:14

The ohv is suitable primarily for very over square engines. THeir short stroke, contrary to popular belief, is very power robbing. The bigger the piston the more room there is allowed for larger valves and the ohv does accomodate better flow. So the increased compression ratio gained at the ohv head and flow makes up for only a portion of the power loss due to the short stroke.

The over square engine is a gimmick that was thrust into motion mostly during the mid 50's due to lowering hood and roof lines of the car (CHEAPER to make). Can anyone imagine how tall the Packard Streight would be if it had an OHV with same block as the Flat head???????? I doubt that slanting it over would do much good. ThIS is why the MoPar 'slant six' was slanted in '58. Lower hood and top required a lower engine height.

Horse power is a function of TWO things, exactly two things and only two things. They are:
Pressure on the piston crown and piston speed.
The short stroke engine is a real slug in terms of piston speed. The OHV makes up for only a portion of it by allowing for a tighter chamber thus higher CR.

It was trade off during the HP revolution of 1955. Eng'ring traded off engine size and weight for a lower profile engine with more CR to accomodate lower profile styling to come in 58 and 59. BUT, GAVE UP POTENTIAL power increase by dropping the long stroke .