Packard Forum Index » General

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 .

Pre-war OHV engines:

Chevy six
Nash six and (possibly) eight
Duesenberg J engine, DHOC, 4 valves/cylinder
Stutz straight 8
Cadillac V-16 and V-12, 1930-'37
Buick straight 8


there's a little starter list, I know there are more.

G'day all, There have been a number of very well researched articles written over the years about whether Packard made good engines and why Packard stuck with the side valve engine. The main reasons which I have noted is that side valve engines tend to be quieter, have a greater engine torque at lower revs, have a lower Octane requirement due to increased intake valve turbulence over OHV engines, and have a higher BMEP (Brake Mean Effective Pressure) in older low compression engines. By way of illustration there was a much publicised match race in about 1930 between a straight eight OHV Stutz and a side valve Lycoming (Auburn?) The Auburn won the match race by a slim margin 102 Vs 101 MPH, after which they removed the muffler from the Stutz and got it to 103 MPH. I can dig out the exact details if you need them. In my humble and always ready to be corrected opinion, it illustrates that in in the days pre hemi heads/ squish chambers/ fuel injection etc, there was not a lot of difference in actual performance between similar sized OHV and SV engines.
There are also some interesting facts about why the US stayed with 6 Volt electrics for so long. Even Rolls Royce went to 6 Volt electrical systems in the US. Best regards Peter Toet

"There are also some interesting facts about why the US stayed with 6 Volt electrics for so long."

HUH???? Did some other country convert to 12v prior to 1955????

To make everyone happy lets not forget the F head as used by early Hudson and Willys (used till 1960) which will make both sides of the subject happy I believe also used in England by RR and Rover.

I think PI and PII Rolls Royce cars were 12V.

Quote:

Interesting thing about that if you look at the 1954 Salesman's Book, they still use that same exact line.

Peter: It is not very surprising that the Auburn won the match race against the Stutz.

The Auburn had about a 15 horsepower advantage over the Stutz SV16. The Auburn had at minimum a 600 lbs weight advantage over the Stutz. The heaviest Auburn produced in 1930 came in at 3900 lbs. The Stutz depending upon coach work had a weight range of 4595 lbs to 5210 lbs. The axle ratios in both automobiles would have a great deal to do with the top speed of both cars.

Since I am classic car fan would it be possible to post a copy of the article. Lycoming automotive engines were produced in my home town of Williamsport, Penna. Lycoming also produced one of the greatest engines of the 1930's the Duesenberg straight eight.


John F. Shireman

ok all you smarties pants, when did briggs&stratton go OHV?

The Vangaurd engine is ohv.