Believe it or not, we try to read every comment on Horsepower Wars Facebook. And it’s come to our attention that your average gearhead gets quite a few things wrong about engines. Here are three things we see the most…

“There’s No Replacement for Displacement”

While this is true for the most part, it’s not really the whole story. Often engine builders will trade displacement for better piston stability at high RPM. A shorter stroke will help an engine rev faster. It’s not nearly as catchy, but perhaps this phrase should have been: there’s no replacement for bore size or there’s no replacement for intake valve size – or even, there’s no replacement for volumetric efficiency.

At the end of the day, if you are using one large valve or two smaller ones to draw air into the engine, that volume or column(s) of air is perhaps the single most important thing. For example, if we had put a displacement cap but not a bore/stroke limitation in LS vs Coyote 3 and allowed for custom billet cranks, then LME could have chosen a 4.125-inch bore and 3.00-inch stroke. And instead of tiny 1.929-inch intake valves, restricted by the bore size, they’d have massive 2.250-inch intake valves – flowing almost 400cfm (over 80 cfm more than ported L83 heads with stock valves).

On the Coyote side, you can see where Ford used this strategy on the Predator/Voodoo engines to increase power. Opening up the bore from 3.630-inches to 3.70 allows at least 1mm larger intake valves and a 20-30 cfm increase from the Predator/Voodoo to the Coyote heads. With a proper CNC porting, Coyote heads can already flow over 340 cfm on the intake. The interesting thing, though, is that when Ford designed the Gen 4 and the Dark Horse’s Coyote – they went back to 5.0L and made just 26hp shy of the outgoing GT350. Will they bring back the GT350, and use another 5.2L block and heads to surpass its previous numbers? We’ll have to wait and see.

If you look at the new Corvette ZR1, GM used a larger bore and shorter stroke (4.104 x 3.15 inches) with a 4-valve, DOHC arrangement to make 1,064 horsepower with less displacement (5.5L versus the base Corvette’s 6.2L) – combining the best of both worlds for this incredible achievement.

“4 Valves and 4 Cams Are Always Going to Be Better”

If this statement were true then they’d be using them in Pro Mod and Top Fuel. At a certain point, simplicity and durability are better. That’s where “more chains than brains” comments start flowing in. Where the Coyote shines is that you don’t need big nasty cams to make 1,800hp. That makes for a nicer start-up and idle, and it also helps flatten out the power curve instead of having a singular, fixed cam timing like a traditional pushrod engine. And of course, the four valves definitely help cram more air into the engine with a small bore and smaller cubic-inch engine.

“You’re Going to Max Out the Turbo”

Well, that’s the idea. Why wouldn’t you build any combination to achieve the full performance from the turbo? Otherwise you are simply oversizing the turbo, right? There really isn’t such a thing as “maxing out” in a certain sense. That said, whenever you build a turbo setup, you do want to size the turbo to be within the sweet spot of the compressor map and have a properly sized turbine to match. When you oversize a turbo, and you are not operating within that range, you ultimately have created a very lazy combination that is difficult to spool on the street or track. And it will never run as fast as it should run at the track. Remember the cam specs, converter, and turbo all work together to spool – sure there are some tricks with anti-lag, but there is more to getting down the track than throwing money at it.

Fun fact: the compressor of a turbo will hit a maximum flow rate and a maximum RPM (before it comes apart or stops flowing more air). Because of the maximum flow rate, there is a bit of a hard limit to the amount of horsepower you can make with a given turbo, but on each engine it could be at different boost levels. The same turbo might make 45psi on a Coyote and 25psi on a big-block Chevy at the same RPM. And that engine combination may simply not be able to hold that much boost – the rotating assembly, cylinder head clamping, or even the block itself. On LS vs Coyote, our goal has never been to break the engines, but that would be the true test of how far you can push them (by going past it to find the breaking point).