This morning I was thinking about V8 engines, and....

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I'd love to have heard the engineering rationale for the relatively quick change in displacement from 313 to 315 and then 318.
 
Single four barrel 315 inch D500 Hemi.

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I'd love to have heard the engineering rationale for the relatively quick change in displacement from 313 to 315 and then 318.
In the early fifties, Chrysler Corp decided to emulate GM and let each brand develop its own motor. So we had a Chrysler Hemi beginning in 1951, a DeSoto Hemi beginning in 52, and a Dodge Hemi beginning in 53, with less-expensive-to-produce poly versions of the Chrysler and Dodge coming 3-4 years later, followed by an all new Plymouth poly in 56. Completely different engine lines, with almost no interchangeable parts, but (as they grew) overlapping cubic inches - i.e., 331 Chrysler, 330 DeSoto and 325 Dodge, or 301 Chrysler and 301 Plymouth.

Chrysler realized having so many different engine lines was a dumb idea, and by the late fifties had consolidated into a corporate big block in low and raised deck versions, and a corporate small block - basically the Plymouth A and later LA. Different cubic inch versions of each, but basically only two V8 engine lines. (Plus sixes, of course.)

The 313 was a Canadian version of the Plymouth poly, the 315 was a Dodge motor.

Why Canadians got a 313 A motor while Americans got a 318 (and in 1956 Canadians got a 303 A motor, while Americans got a 277) - who knows? And why Canadian Plymouths (and 56 Fury) got a 303, while American Plymouths got a 301 (in 57) - who knows?

The above skips over the fact that for 2-3 years some Plymouths and DeSotos got Dodge poly motors, and some Canadian Dodges got Plymouth motors.

Simple, no?

A few years later, Plymouth had to fight like hell just to get a different cam for the Road Runner than the cam in the standard 383. It complicated production.
 
In the early fifties, Chrysler Corp decided to emulate GM and let each brand develop its own motor. So we had a Chrysler Hemi beginning in 1951, a DeSoto Hemi beginning in 52, and a Dodge Hemi beginning in 53, with less-expensive-to-produce poly versions of the Chrysler and Dodge coming 3-4 years later, followed by an all new Plymouth poly in 56. Completely different engine lines, with almost no interchangeable parts, but (as they grew) overlapping cubic inches - i.e., 331 Chrysler, 330 DeSoto and 325 Dodge, or 301 Chrysler and 301 Plymouth.

Chrysler realized having so many different engine lines was a dumb idea, and by the late fifties had consolidated into a corporate big block in low and raised deck versions, and a corporate small block - basically the Plymouth A and later LA. Different cubic inch versions of each, but basically only two V8 engine lines. (Plus sixes, of course.)

The 313 was a Canadian version of the Plymouth poly, the 315 was a Dodge motor.

Why Canadians got a 313 A motor while Americans got a 318 (and in 1956 Canadians got a 303 A motor, while Americans got a 277) - who knows? And why Canadian Plymouths (and 56 Fury) got a 303, while American Plymouths got a 301 (in 57) - who knows?

The above skips over the fact that for 2-3 years some Plymouths and DeSotos got Dodge poly motors, and some Canadian Dodges got Plymouth motors.

Simple, no?

A few years later, Plymouth had to fight like hell just to get a different cam for the Road Runner than the cam in the standard 383. It complicated production.
I never could figure out why all of that happened. Like the 241 Dodge Red Ram Hemi. Why waste all the time and money developing such a small V8? Got to start somewhere I guess.

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My guess is that they were trying to develop flow as an alternative to displacement.

A frequently discussed topic toady on tis very board.
 

I never could figure out why all of that happened. Like the 241 Dodge Red Ram Hemi. Why waste all the time and money developing such a small V8? Got to start somewhere I guess.

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Well, in fairness, that was slightly bigger than Studebaker's first V8 in 51 (232) and also bigger than Ford's first OHV V8 in 54 (239). But Chrysler and Ford and Studebaker all underestimated how large engines would become in the fifties, so none of their early V8s could be enlarged enough to be really competitive. Even the Chrysler Hemi was maxed out at 392 cubes, while the Dodge and DeSoto were undersquare motors by the end (the 325 Dodge had a small bore but a longer stroke than a 440). In 1958, Ford introduced its FE big block for performance work, Chevy got a 348 big block, and Chrysler Corp got its first wedge big block. Studebaker's V8 never got larger than a 289 (and they didn't have the money to develop a new motor). There was no performance development of the Ford Y block or Plymouth poly after 1957, and (I think) the only reason performance development continued with the small block Chevy after 1957 was the Corvette. Then, as we all know, there was a resurgence of small block performance in the sixties, by all of the big three (and arguably even Studebaker with its R1, R2 and R3 motors).
 
I'd love to have heard the engineering rationale for the relatively quick change in displacement from 313 to 315 and then 318.

The engineers would've said, "It isn't broke, don't fix it".

You need to talk to sales, the accounting people, and possibly the customers and competitors about such decisions.
 
The Pantera came with the 351C, not the 400. The 400 was the only one with both small block and big block patterns. Not the Cleveland.

They like to swap and stroke the 400, so they scour for the 400's that used the FMX. Seen a few builds with Aussie heads.
 
The Pantera came with the 351C, not the 400. The 400 was the only one with both small block and big block patterns. Not the Cleveland.
A friend had a Pantera. I got to take it for a short drive one night. Took off from a stop light heading out of town. 135 in third and I still had 4th and 5th! Fun car.
 
FYI, Sunbeams were sold at Chrysler Dealerships. I remember them on the showroom floor at Bucks Garage in Webster Pa when I was a teen.
Rootes group developed the tiger (based on the alpine, obviously) and used Ford engines.
Then Chrysler bought Rootes group....... and since a 273 wouldn't fit, that was the end of Tigers. They did sell more mundane Sunbeams. (Alpines?)
 
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