Coast High Performance 406ci StrokerIn short, I felt like the man who takes a knife to a gun fight. But as it turned out, what I needed for this fight was a big 'stick-a really big 'stick. In fact, "Get the biggest dual-pattern cam you can find," was the first marching orders given to me by Coast High Performance's Shawn Mendenhall. Since this Torrance, California-based outfit specializes in building high-horsepower stroker small-blocks, I listened.
Given that the basic architecture of our starting point was created more than 50 years ago, it would be easy to label this contest "space-age versus stone-age." And there's no denying that GM has created an amazing new line of engines. On the other hand, it turns out that spacemen and cavemen have a lot in common when it comes to what's under the hood. Both engines are overhead-valve, pushrod powerplants, which means they're both air pumps. Get the mixture in, burn it, get it out. It ain't rocket science, for a Gen I engine or a whiz-bang Gen IV.
Therein lay our dilemma. The Gen III/IV engines certainly have improved lower ends, but where they really shine is in breathing ability. How would we match up? The rules of this showdown required that all parts be off-the-shelf...so we reached for the top shelf, going with Dart's fully CNC-ported Pro 1 227 heads. These 23-degree aluminum heads are serious breathers, moving 309 cfm at 0.700 inch lift. Dart calls them "professional-quality competition cylinder heads." Using a 400 block as our basis gave us needed displacement and room for the mondo heads to breathe. So there you have our formula: Big bore, big stroke with 6-inch rods, big cam, big heads, and lots of compression and timing make lots of power.
We did just that, and by the numbers we matched the 402ci LS2, and did it on 91-octane to boot. What's striking, however, is how far we had to go to do it. Race heads, a port-matched intake manifold, and one big hairy cam-and that's just for starters. We might go so far as to call this thing a street motor, but someone might ask, "What street?" and we'd be stuck for an answer. It would certainly be one that's driven without power brakes, since that serious 'stick doesn't provide much in the way of vacuum (6.5-7 inches). And as for idle quality...well, let's not discuss idle quality.
All in all, the component parts of the 402 are rather tame by comparison. Yet the total costs were close to equal. Essentially, we had to build a hydraulic-roller race motor to match the new kid on the block, and that we did. At this point in time, old versus new, it really comes down to what you want with your 583 hp. In human terms, one is a svelte gent, a real James Bond, simply charming until he whips out the newest of Q's gadgets and obliterates your ass. The other is a crude brute, swinging wildly from the trees like a Neanderthal until he jumps down and starts beating you over the head with a leg bone from a brontosaurus.
And there's the question of the hour, friends. Spaceman or caveman? Personally, I like 'em both.
Q&A With Shawn Mendenhall From Coast High PerformanceCHP: We gave you a tough task, building a traditional small-block to match up with a Gen IV motor.
Shawn Mendenhall: GM did well in designing the LS-series engines. The 15-degree heads are such a huge advantage. It would have been nice if we could have used 18-degree cylinder heads.
CHP: It there anything to be said for going old school?SM: The only advantage for the 23-degree setup is the bore. With a larger bore size, it's easier for the heads to breathe, and you can start with a factory block, which you can still get at a swap meet. It costs more to do a 4.125-inch bore in the newer motors, because you need cylinder sleeves and custom pistons.
CHP: What does the future hold for the traditional small-block configuration?SM: Until there's no more gas, people will have fun with them. As long as there's a desire for 23-degree parts and people still have stuff stashed in their garages, they're never gonna go away. Aftermarket blocks are more within the average guy's reach.
CHP: You mentioned 18-degree heads. What are your thoughts on the subject? SM: The 18-degree stuff is old-school racing technology. Make it user-friendly, which is already starting to happen, and it's gonna really change the market. You can make good power with 18-degree heads-they're gonna be able to make a ton of horsepower on the street.