Tracing the differences in engine sizes

198, 225, 260, 273, 289, 300, 301, 305, 307, 318, 326, 327, 330, 340, 350, 351, 352, 360, 383, 389, 394, 426, 427, 428, 429, 440. You can fill in the gaps and there’s a pretty good chance that an engine was produced with a cubic inch displacement (CID) that matches that number.

There are reasons for small engines, medium size engines, and large engines. You don’t have to be a car collector to understand that engines come in different sizes for different purposes. These reasons include the ability to fit into a particular size engine bay, a desired level of performance, and fuel economy. But why they are often so similar in size? Is it simply a function of manufacturing? A marketing ploy? A case of one-upmanship? All of the above?

Is it a coincidence that in the “small block” department in 1969 Chrysler made a 340 engine while General Motors made a 350 engine, and Ford made a 351 engine? Or that in the same year in the “big block department Chrysler made a 426 engine, General Motors a 427, and Ford a 427, 428, and a 429 engine? Not really.

I think that it’s safe to say that the reason that engines are so similar in displacement has more to do with manufacturing needs than anything else. Most of the major auto manufacturers had specific needs for their engines, and these needs were similar from one manufacturer to another. For example, in any given car line, Chrysler had a need for one engine that would satisfy customers looking for optimal fuel mileage, another engine for customers looking for the maximum performance, and yet another engine that was a compromise between the two. For example, the 1969 Dodge Charger was offered with a 225 CID 6-cylinder fuel efficient engine, a 440 CID 8 cylinder performance engine, and a 318 and 383 CID engine that offered neither optimal fuel economy nor performance, but they compromised in both departments.  

Ford and GM would have had the same needs. These requirements would then be passed along to the engine designers, who would be tasked with designing their engines as efficiently and inexpensively as possible. No doubt, with very little variation, engine designers from each of the manufacturers arrived at designs that were very similar, explaining the similarity in engine displacements.

What exactly is engine displacement, and is bigger really better? It is a very common misconception that engine displacement is the total volume of all of the cylinders in the engine. It is not. It is the total volume that is swept by a single piston as it moves from the bottom of its stroke to the top of its stroke, multiplied by the number of cylinders. So you can have an engine with a huge cylinder, but only the amount that is affected by piston movement is counted toward the displacement of the engine.

In general, bigger is better. If you take two identical 1970 Corvettes, or Cudas, or Mustangs, and equip them identically with the exception of the engines, the ones with the large “big block” engines will invariably be faster than the ones with the “small block” engines.

I don’t think that it’s possible to make the same generalization when it comes to engines that vary in displacement by only a few cubic inches, so I don’t think that a difference of a few cubic inches of displacement would be very useful as a marketing tool. This is particularly true considering that buyers who would have been shopping for these “big block” engines would have been the most savvy of buyers, especially about performance.

As mentioned, in 1969 Ford made a 427, a 428, and a 429.

Interestingly, the most powerful of these engines by far was the 427, followed by the 428, with the 429 being the least powerful. I’m not including the “Boss 429” which was designed strictly for racing purposes, and which found its way into very few cars on the street.

Chrysler’s 426 CID Hemi was a monster of an engine, yet it was smaller than GMs or Fords offerings.

When discussing how to improve performance, W.O. Bentley, founder of Bentley Motors is famous for saying “There is no replacement for displacement.” The year was 1927, and to a large degree this rule still holds true today. But rules are defined by exceptions, and there are many to be found in the automotive world.

There are many “small block” engines that are capable of blowing the doors off of “big block” engines. A few examples that come to mind are Chrysler’s high revving 340, Ford’s Boss 302 or Hi-Po 289, and Chevrolet’s LT-1 or DZ-302.

If bigger were always better, then there could be no argument that Cadillac’s behemoth 500 CID engine, which appeared in the El Dorado from 1970 – 1976, would have been the one to beat. But it wasn’t.