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"The Rolls-Royce Phantom IV is one of the rarest motorcars ever built and is the only Rolls-Royce to be powered by a straight-eight engine. The Phantom IV was available exclusively to Royalty and Heads of State. Only 17 cars were built for delivery to customers. The Phantom IV is so highly regarded that, of the seventeen cars delivered, eight are still owned by the original purchasers or their heirs.

Years of Production: 1950 to 1956
Total Produced: 18 "

They not only made a straight eight car, they made an even larger straight eight for military vehicles. This was part of the B range of 4,6 and 8 inline engines.The B81 was a 390 cubic inch 220 horsepower job used in armored personnel carriers.

Intersting to know that RR did make a few straight engines for automotive use.


Two other luxuary car manufactures that used V8 engines Peerless and Cunningham.

John F. Shireman

The V8 had a lot going for it. The Pierce Arrow company seriously considered changing to a V8 but like Packard, the vibration problem turned them away.

Pierce's chief engineer concluded that the V8's power and efficiency depended on its large valve area, after all the V8 had 16 valves where the 6 only had 12.

He calculated that he would need 3" valves to match the V8. This was impractical from the standpoint of weight and cooling, so he tried 2 valves of 1 1/2" diameter instead.

The new dual valve 6 matched the V8s in power and economy. Plus the new light valves and valve springs made the valve action practically noiseless, while reducing wear to a minimum and thus increasing reliability and extending engine life between overhauls.

This engine powered Pierce Arrow's largest most expensive models from 1918 until 1928, when they replaced it with a straight eight.

It is interesting how a similar stimulus led Pierce and Packard to a similar line of research but totally different end results.

Rusty, sure enjoying this posting exchange. I believe Pierce Arrow made large six cylinder engines approaching a liter per cylinder, or more. This approach gave them smooth and powerful engines without the complications of eight cylinders.

A good read - I think the only real advantage for a V8 over a straight 8 might be that it's easier to get more equal intake breathing between cylinders. big difference between the distance from the carburetor to cylinders 1 and 8 vs 4 and 5.

In general, the V8 has some internal space restrictions relative to amount of stroke that be obtained vs cam clearence vs the additional bank of cylinders for the crank and rods to spin in. Among other restrictions.

Prior to the hp revolution of 1955 the public demand for sustained high speed operation was nearly nil. Styling such as hoods and pontoon fenders, narrow frames and so-forth did not lend well to large V8's due to width.

Engine rpm was limited to rather low rpm due to metalurgy and manufacturing cost constraints. So the inline engine could be tall for the prewar cars that were relatively tall cars but rather narrow hoods and frames.

The inline engine is LONG stroke and low compression (hence flat head) tall, long and narrow. While short stroke high compression OHV V8's are for wide,low and short cars.


Hp is a function of 2wo independent forces;
Pressure on the piston crown.
PISTON SPEED.

In the prewar era materials developement for strength was
somewhat obscure. So the engineers opted for lower compression and LONG STROKE for HP AT LOWER RPM!!!!.

Enter WWII and a phenominal amount of R&D discoveries came about in terms of materials and mfg techniques.

Essentialy, the V8 is a cheap way to build relative to a shorter, lower and marginaly wider car.

The inline 6 into the 1980's was just a carry over from many years of perfecting and mfg'ing tooling.

NOTE that hte MoPar slant six is slanted over for hood clearence. IIRC it is a relatively long stroke engine.

So, in regards to the original question in post #1 above. Is the Packard streight 8 a stronger engine in terms of CID and HP than the Cad V8 or other V8's of the same period???

Rusty O/ Toole; I have a question for you that I hope you might be able to answer.

When Packard introduced the straight eight in 1923 the engine used three ring aluminum pistons. Sometime later Packard dropped the aluminum pistons in favor of four ring cast iron pistons. Why would they have done this.

John F. Shireman

John, the 320 and 385 engines at least as far back as the 6th series used aluminum pistons with 4 rings; whether this continued all the way to 1939 on the Super Eight I'm not sure w/o checking the parts book. Cast iron pistons were used in 1942 as the war curtailed the use of aluminum. Is this perhaps what you had in mind?

PS - sorry for responding John, I see you only wanted comment from Rusty.

"So, in regards to the original question in post #1 above. Is the Packard streight 8 a stronger engine in terms of CID and HP than the Cad V8 or other V8's of the same period???"

I believe that all through the 1930s and at least through the early 1940s, the Packard I8 was bigger (more cid) and had more horsepower than the Cadillac V8. (Assuming we're comparing with Packard's "senior" 8)
In fact, Packard's Speedster 8 from 1930 (Model 734) was not that far behind in horsepower than Cadillac's V-16; 145hp vs 175hp, although it is thought that the V-16 is what took all the wind out of the sales of the Packard Speedster program, and the Speedster was never really marketed and soon dropped after less than 150 built.