Rat vs. Mouse

More Power. The performance quest has always led horsepower junkies on a search not only for more power, but also for the least amount of coin. Anybody can throw money at a project and end up with an impressive engine that makes gobs of power. The art comes in when you can build an engine that makes serious power and do so for less than conventional wisdom dictates.

Years ago, CHP performed a heads-up contest pitting a 408ci Rat against a 408ci small-block (Rat Versus Mouse). Even with rules like iron heads and the same camshaft and header sizes, the Rat motor clearly won this shootout with 464 hp and 465 lb-ft of torque against the Mouse motor’s valiant but losing 423 hp and 443 lb-ft of torque.

We still receive letters about this contest, offering suggestions on how to make the comparison more even. Frankly, no matter what we do, the Rat motor always wins. Big-block heads have larger ports, the valves are larger, and flow is far superior. Over the years, CHP has performed more than 60 small- and big-block cylinder head flow tests. If you will accept the fact that higher flow bench numbers virtually guarantee more power, then it doesn’t take long to figure out that even a stone-stock, oval-port Rat head from an ancient 396 can flow more air than most hot aftermarket small-block heads.

For example, a stock production 049 oval port big-block iron head with stock valves starts life with a 253cc intake port and flows 232 cfm at 0.400-inch and 250 cfm at 0.500-inch valve lifts. To equal those numbers a small-block requires an aluminum aftermarket cylinder head like the Air Flow Research 180, Brodix -8 Pro, or a TFS 195cc head, all of which are more expensive cylinder heads with smaller 2.02/1.60-inch valves. Add in the larger 454 bore, and the big-block’s advantages just keep adding up. Since cylinder heads are the key to any performance endeavor, it’s clear that attempting to create a level playing field between a small-block and big-block is probably a waste of time. So we decided to look at the classic confrontation between the Rat and Mouse from a monetary perspective.

Ultimately, when you stomp on the throttle of any hot rod, it’s the power curve and the drivetrain that determine how well it runs. The more power you make, the quicker and faster your car will run. The old wheeze “power costs money—how fast do you want to go?” will always be true. If we were all rich, we’d probably all be driving gas-guzzling big-blocks. But because most of us have champagne tastes and soda budgets, the small-block is often the economical move. So we decided to look at these engines from a power-per-dollar standpoint. But before the big-block folks pull out their poison pens and accuse us of Mouse bias, let’s start by admitting that right out of the gate.

Yes, the small-block does have a distinct advantage >> in this category. However, we are not here to convert anyone from one camp to the other. We’re here to present the facts and let you decide on your engine of choice. Small-block parts are less expensive and plentiful due to basic economics. With a huge demand, manufacturers build large numbers of parts. Through economies of scale, they can afford to build these parts very inexpensively, which means they can pass those savings on to the consumer. That’s why a small-block crankshaft or cylinder head costs less than a big-block. There is more supply, so the cost comes down.

We’ve assembled several interesting viewpoints for evaluating big-blocks and small-blocks. The idea is to look at these different engine combinations from both the power and price standpoints. Sure, we’d all like to have a supercharged big-block that makes 1,000 hp and idles like a stocker, but then minor inconveniences like eating and rent intrude into our best horsepower daydreams. Yet despite the realities of life in the 21st century, there are ways to build a fun-to-drive engine that doesn’t cost a ton. It all depends on how much you’re willing to sacrifice to attain your goal.