Rodent Wrestle Fest - Tech

The headline could have screamed "David Slays Goliath" or perhaps "Mouse Slays Rat! Film at 11!" In our Rodent Wrestle Fest, the engine theorists were laying bets that the small-block, with its painfully smaller heads, would make great torque, but those monster rectangle port heads and sewer pipe-sized valves in the Rat motor would steamroll the little motor when it came to peak horsepower.

The combustion prognosticators were close, but surprisingly, the small-block made more power than the Rat at every point except three. Are you surprised? We were (a little) and along the way, we learned some very interesting stuff. There's far more to this story than just a same-displacement comparison with a glance at peak horsepower, peak torque, and average power numbers. Here's what we found.

Round 1In our first test, we bolted the World Products 454ci small-block up on Westech's dyno and outfitted the engine with a Holley HP-series 850-cfm carburetor, a set of 131/44-inch headers, a complete 3-inch exhaust system baffled by a pair of Flowmaster 50-series mufflers, and water circulation handled with Westech's electric water pump. This engine is actually no stranger to the pages of Car Craft nor to Westech's dyno. In fact, this same engine spent serious time in the Project SuperNova engine bay and on Westech's same dyno, making an impressive 610 hp and 584 lb-ft of torque on 91-octane pump gas.

But wait a minute! Looking at our dyno sheets, we "only" made 574 hp and 556 lb-ft of torque, so what happened? First of all, those dyno tests were performed using a much larger 1,050-cfm Dominator carburetor, while great for peak hp numbers, a 1,050 carb may not be the best for the street. More importantly, between the time that Hot Rod tested this 454 Mouse and our subsequent testing, Westech discovered its shop barometer was reading low, making the horsepower correction factor they used a bit inflated. According to Westech's dyno master Steve Brule, this was about four to five percent. Applying a 5 percent correction to 610 hp equals 580 hp-or a little more than 1 percent higher than our dyno numbers. 'Nuff said about that.

If you look at the small-block power numbers, the hefty Mouse delivers outstanding torque, over 500 lb-ft of grunt from 3,000 all the way up to 5,900 rpm! With the Crane solid-lifter flat-tappet cam, peak power occurs at 6,300 with a power band between peak torque and peak horsepower of a decent 1,600 rpm. The excellent torque is due primarily to the "small" (compared to the Rat motor's rectangle port heads) 220cc intake ports actuating 2.125-inch intake valves.

But rather than get any deeper into the small-block numbers, let's take a look at how the Rat fared.

Round 2Bolting the big-block rodent up on Westech's SuperFlow dyno, we used the same size 131/44-inch headers, the exact same MSD ignition and distributor, along with the identical 850-cfm Holley carb. After the requisite timing and jetting adjustments for peak overall power, it was time to yank the handle for the power comparison.

While most Rat fanciers won't like these results, the power numbers instantly revealed that the Rat's larger intake ports prevented the larger rodent from generating equal or better torque numbers, while we were somewhat surprised that the Rat wasn't able to make up for this at the top end. Some power pundits had offered that the larger Rat ports would support a top-end hero horsepower charge, but that didn't materialize, giving the same-sized Mouse the overall win in every category from peak and average torque, as well as peak and average horsepower.