Packard Forum Index » V-8 (1955-56)

I was reading through the Specifications section of my 55/56 Shop Manual. I noticed that the 55 Clipper Custom was rated at less horsepower than the 55 Patrician, but they seem to have the same engine, same carburetor, and with the optional dual exhaust, the same exhaust system. What is the difference between the 55 Clipper Custom 352 and the 55 Patrician 352? Many thanks for any thoughts.

My guess would be different camshaft profiles or possibly compression ratio?

Could be the camshaft, but the compression ratio is the same.

All valve & timing specs are same also. I wonder if because the car was lower priced and normally supposed to have single exhaust and lower axle ratio, in order to keep the illusion and justify and keep the higher priced buyers happy, they conveniently didn't mention the specs would be same when optioned up--although I don't know if the exhaust would account for 15hp as that does seem the only difference. It was the 50's after all and without SEC, FTC or whatever "C", you could get away with almost anything.

chuck -

Distinctions in HP among the various engines used in 1956 models always made perfectly good sense to me (if only from a gut feeling), but I never stopped to consider the '55s.

You bring up an interesting point as the complete engines as used in the Clipper Custom (5660 chassis) and Patrician and Four Hundred (both 5580 chassis) are one in the same, according to the parts book. They used the same Rochester 4-bbl. carb and Delco distributor, as well.

The exhaust system might be the only difference, with single vs. dual. The Specifications section of the shop manual shows only minor differences between the optional dual system on the 5660 chassis and that used on the 5680.

Yet, was the exhaust factored into gross HP back then?

SAE gross horsepower was a bare engine on a dyno - no accessories, no air cleaner, no exhaust, corrected to standard temperature and barometric pressure.

The fifteen horsepower difference was an advertising ploy to sell the higher priced car.

thnx, jack vines

If you go to page 85 of your '55-'56 parts book, under group no. 5.0504 GASKET-HEAD: there are two head gaskets listed,

440469 ALL 55TH;5640-60-70 but not -80
440976 5680-88

in group 5.50547 we find the heading SHIM-CYL. HEAD GASKET
440884 5560-80..........FOR LOW COMPRESSION RATIO.......
6480755 ALL 56TH.........FOR LOW COMPRESSION RATIO.......

I'm thinking they put the Hash "fatter" head gasket on to lower the compression ratio?

Opinions?

A new head gasket (P/N 440976) was necessary for the larger bore of the 374 for the 56th Series - 4-1/8" as compared to 4" in the 352 engine. I'm guessing they were able to use the same head gasket for the 320 and 352 engines in the 55th Series.

Application of shims merely seems to follow the head usage - 55th vs. 56th. I could swear I read something published by the factory about the use of these head shims, but darned if I can find it in my files right now.

Meanwhile, check page 90 and you'll also find low compression pistons for the 352 (in 5560-80; 5640-60-70) and 374 (in 5680-88) - though only in standard and .010" over.

Interesting observations, but they don't account for difference in horsepwoer on 55th Series 352 engines.

Funny, after all these years, that this HP "scam" wasn't previously exposed in print.

The factory recommended the use of the head shims in '56 cars to lower the compression ratio for areas that didn't have quality fuel. There's a '56 STB on it somewhere. They also recommended retarding the timing.