How were early 70’s V8’s so large yet relatively lacking in power

Question

How is it possible with the Chevy’s and Caddy’s with their pure American 6 litre V8’s didn’t get past 300 horsepower.

It seems so implausible that such a massive engine was so inefficient.

In: Engineering

Answer 1

There’s a *bunch* of factors that all make those V8s bad. The core concept of an internal combustion engine is to push old air out of the cylinder, replace it with fresh new air/fuel mixture, compress and blow it up, and use the energy from that to push the car forward. Those engines have issues at every step of the process:
– They don’t really manage to push all the air out of the engine. There’s a concept in engines known as volumetric efficiency, which is the ratio between your displacement and how much air you actually get rid of to replace with new air. For a variety of reasons, they aren’t great at this.
– Coupled with that, they aren’t able to feed more air to the engine at “high” RPMs. By around 5000 RPMs, a Chevy L58 (5.7L engine in many performance applications, also known as a 350 Small Block) will be perceived as out of breath, failing to deliver enough fuel/air mixture to the engine.
– Between the low volumetric efficiency and the fact that it gets worse at high RPMs, your 6L engine doesn’t *actually* bring a lot of fuel/air mixture in per second. A higher-revving, more efficient modern engine can move a lot more air and fuel despite being smaller – because it’s better at replacing old air and able to deliver enough air as the engine keeps revving higher.
– Once the fuel/air mixture gets into the engine, it needs to actually be combusted. We have gotten a lot better at this, and old engines were just not as good at combusting all the fuel and getting it to release energy. Fuel injection and modern engine control units are largely there to make it combust *really* well, and these engines have neither.
– Then, we need to actually turn all this heat into useful work – but there’s a bunch of things stopping us. Most notably, there’s friction in the way – friction in the valvetrain, friction between the pistons and the cylinder walls, friction on the way down to the crankshaft and so on. That friction steals power from us, and we have gotten better at reducing it.

TLDR: Newer engines bring more fuel and air into the cylinders, get that fuel to release more energy when it’s ignited and lose less energy to friction.