'We've never worked harder for a simple 500 hp, once again proving that sleep is a waste of time.But we do the heavy lifting so you don't have to, and by the time we finished maiming four or five small-block Chevys, we finally found the magic combo that allows us to say, "Here's the engine anyone can bolt together to make a cheap and easy 500."
The quest began when the Disco Nova needed a powerplant. We painted our project '77 last month and now we're starting on the mechanicals, so it's a backward deal from the get-go. In keeping with the anyman's theme of the buildup, we sought a package of budget bolt-ons that would work with a stock short-block to make enough power for low 12s in our hefty X-body. Little did we know where that path would take us, as the 500 number became an obsession. Besides, we needed the number to justify the cover blurb that made you choose this particular rag rather than the editorial stylings of, say, Super Chevy. Now see if you can follow along.
Dart Small-Chamber Iron Eagles
Circle-track racing is where ingenuity is realized in cheap speed parts, and that's where we found Dart's new budget cylinder heads: Iron Eagles with combustion chambers advertised at 49 cc's.
To bump up compression in classes that mandate flat-top pistons, racers find the heads with the thickest decks then mill the wee out of them and use flat-faced valves to make the smallest possible chambers. The heads are often angle-milled, which means taking more material off the exhaust side of the heads than from the intake side. This allows even smaller chambers and also rolls the valve angles a bit to move the valves away from the cylinder walls for slightly better airflow. The process wreaks havoc at the machine shop because all the intake-surface angles and head-bolt seats need to be reset after the heavy mill jobs, but Dart now offers iron performance heads with all the tricks for the smallest chambers worked into castings designed for the job, so intake fitment is not a debacle. The decks are also thick to prevent head-gasket sealing problems. The tradeoff is that the Iron Eagle heads each weigh a good 8 pounds more than stock Chevy smog-era castings.
What does this mean to you? It's a whole new world of opportunity for virtually any flat-top small-block Chevy thanks to one thing: compression. The small-chamber Dart heads are advertised to have 49cc combustion chambers, though we measured our set at 54 cc's (the number varies depending on the valves used; the deeper the dish on the faces of the valves, the bigger the combustion chambers). Even with 54 cc's, an average 350 with stock dished pistons jumps from about 8.5:1 to 10.5:1. If you've already built a 383 with zero-deck pistons and 64cc chambers for around 10.5:1 on pump gas, the Dart heads get you 12.0:1.
For 283s and 327s, the only way to get decent compression with normal heads and off-the-shelf pistons is to use the old Speed-Pro designs that usually require hand-shaping of the domes to make them fit the heads. Now you can use the cheaper and more readily available flat-tops. With the Dart heads, a 283 with flat-tops can make 9.4:1 with the same pistons that used to make 8.3:1 with 64cc combustion chambers. The same deal on a 327 makes 10.5:1 rather than 9.3:1. The small-chamber Iron Eagles are available in intake-runner sizes of 180, 200, 215, and 230 cc's to match any displacement and rpm range.
Summit sells assembled sets of Iron Eagles for a little over $1,000, but circle-track shops (see eBay Motors) sell assembled sets as cheaply as $720 depending on the quality of parts used. Racepartsdirect.com will toss you a complete set with mechanical flat-tappet springs, 71/416-inch studs, and guideplates for $850. That makes them just slightly more expensive than stock Vortec heads machined for lift clearance, big springs, studs, and guideplates.