According to a General Motors Press release the new EcoTec3 line of truck engines (a clever re-branding of the old Vortec line-up) includes a new V6, but you may not know it or hear much about it and here’s why.
For decades now General Motors fullsize trucks have soldiered on with the same basic V6. A stay over from the malaise-era, when GM decided the best way to get into the small displacement 6-cylinder market was to essentially engineer a V6 that was 3/4 of it’s v8 brethren. This isn’t a new, or generally bad technique; It worked great for the 3.8L Buick V6. I’m sure most readers are aware of this, as most people will explain the design of the ubiquitous 4.3L as a “350 with two cylinders chopped off”. This isn’t necessarily true, but it definitely shares the 350’s bore and stroke, it’s 90* V-spread and they usually shared the same technology for heads and fuel delivery. For all intensive purposes, it was part of the family.
Now, unless you’re really big on malaise era-GM, you may not know that the 4.3L wasn’t the only V8-into-V6 experiment. It just happened to be the newest, and largest displacement (good for trucks, didn’t have to compete with the Buick V6) and as a result was very popular in this segment. The other 90* V6s were often found in A-bodies and F-bodies. The first one introduced is actually the most interesting because it was a V6 before it’s bore and stroke combination became a V8. With a 3.5″ bore, both the V6 and V8 were undeniably the worst performing engines in their respective families. The other 90* V6 used the 305 V8’s bore and stroke. It’s often forgotten, likely because it displaces 3.8L just like it’s Buick counterpart. What’s most interesting is that none of the 90* V6s were made available alongside one another, each larger displacement model replaced the last.
So what makes General Motors’ announcement of the above 262 cubic inch, 4.3L V6 so exciting? Well if the title of 285 fucking horsepower (more than any Gen I SBC ever installed in a truck) doesn’t impress you, maybe the 305 ft lbs of torque will. This thing is a tire roaster.
What’s most impressive is that it’s done with less bore and more stroke. Now, most automotive “gurus” will like to sell you junk-science on how a big bore is great for more horsepower and a long stroke is great for making more torque. Anyone that has ever worked with BOP motors or has any amount of common sense will tell you that this is an old rule of thumb that was outdated many decades ago and somehow just never forgotten. Chances are it’s going to be Mr.Smallblockchevy that’s going to be feeding you this line, and as you read above when I was speaking about the 3.5″ bore, he’d be totally right – when he’s speaking within his wheelhouse of information and technology.
Anyone that has ever had interest in building a hot motor for a car has likely learned that the runner, bowl, short side radius and combustion chamber configuration plays a large part in making power. It’s the idea behind what makes the 96+ Vortec heads so great. Something else that they may not be aware of though – which is just as important – is the valve geometry. The angle of the valve in relation to the piston face and the position within the chamber do wonders for the engines ability to breathe with a bore that would be seen as “less than adequate” to most small block Chevy guys. GM knew this and that’s why the valves on any generation III or newer head have at least a 15* angle (as opposed the much less acute 23* angle that was standard across all factory Gen I and II heads.)
So with it’s 3.92″ bore it’s able to make much more power than the old 4″ bore 4.3L. The same goes for the 5.3L V8. With it’s nearly 305-like 3.78″ bore it is able to make 355hp at 5000 rpm in it’s new Gen V trim. It’s not all in the heads though, these motors use high compression ratios with all aluminum components and direct injection to reduce the risk of detonation under load as well as a very slick runner and combustion chamber design. This isn’t grand-pappy’s old, oil-spitting Chevy engine.
So if you ever go to test drive a new half-ton Silverado or Sierra, don’t fear the base model engine. Engineering wise, it’s a keeper.