'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.
The Leaker: 470 HP For $2,350Our first scheme was by far the most pure: Make big power and keep it cheap by bolting speed parts to the engine that came out of our Nova, reusing all the critical hardware and stuff. That fell apart when the Nova mill was too grimy to clean up in time for the deadline. We cheated by using a short-block you may remember: It's the 350 from our El Cheapo '72 El Camino, and it had gone high 12s on nitrous. The last place to assemble this thing was Chevrolet, so it was totally legit.
We were geniuses up to the point that the valve-to-piston clearance was nonexistent. The Dart heads are milled to such an extent that the edges of the intake valves stand proud above the deck surface, whereas a stocker might be sunken into the chamber by 0.060 to 0.100 inch. This takes up valve-to-piston clearance quickly, especially when the valve sizes are 2.050/1.600 and you're cramming them into stock cast pistons with undersized valve reliefs that are in the wrong places.
We consulted Lunati for a cam that would work with limited valve-to-piston clearance but still meet our 7,000-rpm goals. The best fit was PN 40115, an older cam with slower ramps. The area of least valve-to-piston clearance was within 10 degrees on either side of TDC, with the cam at about 0.250-inch tappet lift. Therefore, we needed a cam with steep duration at 0.050 but not too aggressive at 0.200 to 0.250 inch. The Lunati 40115 is a solid flat-tappet with 259/268 at 0.050 on a 106-degree lobe separation angle and just 0.519/0.531-inch lift and a loose 0.030 lash setting.
But it wasn't enough. We needed more valve-to-piston clearance, so out came the die grinder and a carbide bit to whittle aluminum off the top of the pistons with them still installed in the engine. Stock cast-piston tops are roughly 0.350-inch thick, and we maintained the depth of the stock valve reliefs but made them much larger. Butchery, to be sure, but it works, and we'd have even felt OK about throwing a 150 shot of nitrous on top of them.
By the time we were done, we figured we'd enlarged the 12cc dishes in the stock pistons to 13 cc's. The pistons were 0.032 inch below the deck surface of the block, robbing precious compression ratio. Some of that we regained by using Fel-Pro steel-shim head gaskets, which have a 0.015-inch compressed height and 4.100-inch gasket bore as opposed to the common composition gaskets at 0.041-inch compressed height and a 4.185-inch bore. Even with thin gaskets we had a massive 0.047-inch head-to-piston clearance. We would have liked a tighter quench of about 0.037 inch, but the pistons were too deep in the hole. The compression was a depressing 10.77:1. Far better than 8.5:1, but we hoped for 12.0:1.
We took it to the dyno anyway. And you know what? It ran dang good. We topped our conglomeration of used junk and hacked pistons with the small-chamber 215cc Dart heads, an 850-cfm Speed Demon carb, a Mr. Gasket 2-inch open-style carb spacer, and an Edelbrock Victor Jr. single-plane. We used 151/48-inch-tube Flowtech headers (that needed lots of bashing to clear the angle-plug heads) with 18-inch collector extensions, and we tossed in the Nova's grimy HEI-which everyone said would give up at 5,500 rpm-plus some used plug wires. The lump put up a decent 469 hp, pulling hard to 7,000 rpm. The power was so flat from 6,300 through 6,800 that it's tough to quote an exact peak rpm.
The carb wanted 81/86 jetting, the 2-inch spacer was critical, and the headers wanted the Hooker 18-inch collector extensions rather than the cheaper 12-inch Flowtech ones. The timing was best at 36 degrees total, and the HEI's curve was so slow that all the timing wasn't in until 4,000 rpm. We learned that the Edelbrock Super Victor was way too big for this engine (it killed as much as 15 hp compared to the Victor Jr. with the spacer), and we saw identical power curves with either VP C14 fuel or Rockett Brand 93 octane. Windage did not seem critical, as power was unchanged whether we ran 5 or 4 quarts in the pan (we often find a little power running a quart low). We ran Royal Purple oil in a heavy 20W50 thanks to the engine's blow-by. Though every cylinder cranked a decent 170-180 psi, this thing smoked badly through the borrowed valve covers. Ring seal was nada.
In retrospect, 1.34 hp/ci is impressive for an engine with a bone-stock bottom end and what later proved to be 0.010-inch bore taper. Besides, we'd managed to make nearly 470 hp for a total investment of $2,341.18. We just hadn't hit that magic 500hp number, and we set out to find it. Even if it involved some thieving.
King's 350: 515 HPIt was three days before the magazine shipped to the press, and we needed a quick solution to bad ring seal. If we were going to put rings in it, we might as well throw in some slugs too. Aftermarket pistons could buy some needed valve-relief depth as well as pick up the compression. Dulcich is the master of hand-cut valve clearance, so we even considered a standard-bore set of Speed-Pro L2256 pistons that could handle lots of cutting (and would need it) and that we could install after a simple bottle-brush hone. It wasn't the most reasonable solution, especially with a huge ring ridge at the top of the cylinders of our 350. It seemed we'd need to bore the thing.
Then it struck us: Matt King built an engine with exactly our mindset when he was the Car Craft editor. It was based on a standard-bore ZZ4 that just took a hone and a deck cut to get nearly 11.0:1 compression using Probe pistons with decent-valve reliefs and, best of all, 3.5cc domes. King had left town with the engine in storage, and he left us the key. When we found his 350 on a rolling engine stand with a lift plate bolted to the carb pad, we figured that constituted both destiny and permission. It was exactly the type of stock short-block we'd have built, plus it had a Milodon pan, so we nabbed the sucker.
A day later, our top end was bolted to the fresh 350 with the Probe dome-tops squeezing almost exactly 13.0:1 with the 54cc chambers, 3.5cc domes, and new Fel-Pro gaskets with 0.039-inch compressed thickness. Ahhhh, perfect-except valve-to-piston clearance remained a problem. King's monster Lunati 259/265 at 0.050 cam wouldn't fit; neither would our earlier Lunati stick. We were determined to make this one a bolt-on with no hashing of the pistons, so a thrash test-fitting of five different cams finally found us with a Comp Cams 292S, a solid flat-tappet with 248/248 at 0.050, 0.525/0.525 lift, and a lobe sep of 110 degrees. That cam had just enough valve-to-piston clearance with the Probe slugs at 0.005-inch below the deck and the 0.039-inch-thick head gaskets. However, we lost a small battle when the piston domes barely contacted the cylinder heads, a problem easily solved with 10 minutes of grinding minor divots in each chamber.
With more compression, better ring seal, and a smaller cam, would we make our number? Yep: 515 hp at 6,800 rpm and 457 lb-ft at 5,200. With 13.0:1, it only runs on high-octane gas, but we were able to run without detonation on Rockett Brand 100 octane that you can buy at the pump in some parts of the country. Inconvenient perhaps, but compression is your pal when trying to make big power with budget cylinder heads and flat-tappet cams.
So there's your combo: 850 carb, Victor Jr., Dart 215cc small-chamber Iron Eagles, a Comp 292S, Probe 3.5cc domed pistons, and a bone-stock bottom end for a guaranteed 500 hp for less than $3,500. Where are you gonna beat that without nitrous? Wanna know how quick it can be? Us too. Come back for the next few issues as we stab this thing in the Disco Nova and make some passes. Just don't tell Matt.
IRON EAGLE POWER LEAKER 350 KING'S 350 LB-FT HP LB-FT HP 4,000 400 305 417 312 4,{{{100}}} 398 311 419 317 4,{{{200}}} 402 322 426 327 4,{{{300}}} {{{405}}} 332 439 341 4,400 410 343 445 359 4,500 413 354 447 372 4,{{{600}}} 415 363 448 383 4,700 418 374 449 393 4,800 423 387 451 402 4,{{{900}}} 424 395 455 412 5,000 425 404 457 424 5,100 423 411 457 435 5,200 423 419 456 444 5,300 421 425 455 452 5,400 418 430 453 459 5,500 415 435 450 466 5,600 413 441 449 472 5,700 411 446 446 479 5,800 407 450 444 484 5,900 403 453 443 491 6,000 399 455 439 497 6,100 397 461 434 502 6,200 394 465 429 504 6,300 390 468 423 508 6,400 385 469 418 509 6,500 379 469 414 513 6,600 373 468 409 513 6,700 366 467 404 515 6,800 361 468 398 515 6,900 352 463 388 508Bonus Power: 383 TestIn the course of our thrash we got derailed a bit and tried the Dart 215cc small-chamber heads on a cast-crank 383 we had in stock. This engine used a Comp 306S solid flat-tappet cam with 260/260 at 0.050 and had forged Keith Black flat-top pistons set at zero deck. They, too, needed lots of handwork to get sufficient valve-to-piston clearance. Compression wound up right at 12.0:1, and the power with the Victor Jr. intake, 2-inch spacer, and 850 Speed Demon was 530 hp at 6,600 pm and 497 lb-ft at 4,900. We also ran it with an Edelbrock Street tunnel-ram and a pair of 650-cfm TR Demons and made significantly more power: 568 hp at 6,600 and 512 lb-ft at 4,600 with gains everywhere in the rpm range.
While the 383 made more power than the 350 (duh), its hp/ci was not quite as good and its rpm rolled off sooner. We'd conclude that the 215cc Iron Eagle is a little happier on the smaller engine when turning in the 6,000-plus rpm range, so we'd select the 230cc intake runners if we were going to do it again.
WHAT’S THE DAMAGE? DESCRIPTION PN SOURCE PRICE STAGE 1: 470 HP 850 Speed Demon 1563010 Summitracing.com $439.00 Mr. Gasket 2-inch spacer kit 6007 Summitracing.com 29.95 Edelbrock Victor Jr. 2975 Summitracing.com 185.95 Intake bolts and washers N/A Local hardware store 2.04 Fel-Pro intake gaskets 1206 Summitracing.com 14.88 Dart 215 Iron Eagle 10511122F Racepartsdirect.com 850.00 0.015 Fel-Pro head gaskets 1094 Summitracing.com 39.76 Fel-Pro valve cover gaskets 1603 Summitracing.com 11.95 Lunati 259/269 solid cam 40115 Summitracing.com 159.69 Lunati solid lifters 70992 Summitracing.com 89.95 Lunati 7.900-inch pushrods 83133 Summitracing.com 82.99 Comp Cams {{{Magnum}}} rockers 1412-16 Summitracing.com 143.88 Poly locks for 31/48 studs 4601-16 Summitracing.com 43.39 {{{Summit}}} timing set G6600 Summitracing.com 31.95 Mr. Gasket fuel pump block-off 1515 Summitracing.com 5.50 Flowtech headers 11100FLT Summitracing.com 96.95 18-inch collector extensions 11230HKR Summitracing.com 54.95 Royal Purple 20W50 (6) RP01250 Summitracing.com 34.50 K&N oil filter HP-1001 Summitracing.com 9.95 VHT Chevy Orange (2) SP123 Summitracing.com 13.98 TOTAL $2,341.21 STAGE 2: 515 HP Minus parts not used (1094 gaskets, cam, lifters) –289.40 {{{Probe}}} forged pistons 13721-STD PAW 509.95 Hone N/A Speed-O-Motive 160.00 Deck N/A Speed-O-Motive {{{100}}}.00 Rings, bearings, gasket kit N/A Speed-O-Motive 185.00 ARP rod bolts 134-6003 Summitracing.com 59.88 Comp 292S cam and lifters CL12-224-4 Summitracing.com 189.95 Milodon oil pan 30902 Summitracing.com 153.95 Milodon oil pickup 18314 Summitracing.com 34.88 Milodon pump shaft 23050 Summitracing.com 13.95 TOTAL $3,459.37