As they say, “bigger is better,” and today, with the ever-increasing displacement of small-block engines, it applies even more to big-blocks. After all, why build a 396 or 454 big-block when it’s fairly easy to get that sort of displacement from a lighter weight small-block? Besides, the overall cost to build bigger isn’t that much higher and the benefits in overall power potential, especially torque, is huge.
When we started penciling down this big-block build we decided on a few parameters. First, it needed to be geared for the street. Meaning it had to have a decent idle and live on 91 octane that passes as premium here in California. Second, it had to have a broad, flat torque curve, especially in the low to midrange area most street engines live in. After pondering a bit, it seemed like a big-displacement hydraulic-roller engine was in order.
If you haven’t noticed, good condition big-block cores are becoming increasingly hard to find, but fortunately Dart Machinery offers Big-M blocks that are perfect for someone who wants to shun the LS trend and do something a bit more retro. Their Sportsman line is well suited for a street engine build and at around $2,000 it’s pretty affordable as well. But, the most important aspect of the Dart block is that it’s able to go to displacements unobtainable for OEM offerings from the General.
After chatting with Jack McInnis over at Dart, we came up with a 540ci big-block. Sure, we could have gone even bigger, but 540 is a lot of cubes and more than enough for the typical street bruiser. All the parts are available right off the shelf, and it’s a proven reliable combination. After ordering our block we contacted JR Twedt of JR Competition Engines, to help us with the machine work and assembly. Twedt says, “The Dart Big-M block is hands down the best choice for big-inch engines. The main lines on these blocks are always spot on from Dart, which is really nice considering the labor intensiveness that goes into having to line-bore the mains. A couple more great things about the Dart Big-M are its strength and versatility. You can take these blocks out to 4.600 inches with ease and not have to worry about thin cylinder walls because of the extra-thick siamese cylinder walls.” We also decided to make life easy and stick with a hydraulic-roller camshaft. Sure, this leaves some of the 540’s potential on the table, but we feel that for a street engine it’s a trade-off worth making.
Twedt says big-inch 540ci engines love compression and camshaft. Now this is a street application, so it needed to stay in the 91-octane range at 10.5:1 compression. The whole street aspect also dictated the general size of the camshaft. As Twedt says, “Combination is everything—not just the cylinder heads and cam combination, but how all the parts work together. The big lift, big duration, and huge cfm flow numbers are cool to look at, but it doesn’t mean much if it’s used incorrectly. After all, nobody drives a flow bench down the road or racetrack.” This is why it’s important to think about how an engine will be used before ordering parts and piecing it all together. If our goal was a quarter-mile race car then this big-block would have been built completely different. The goal here is a well-mannered street engine that could hit the occasional dragstrip or autocross. This isn’t a cookie-cutter build, which is why we used an engine builder rather than flipping open a catalog and buying someone else’s idea of what we need. Besides, doing it this way is much more fun.