The solution in such a case is to upgrade with more suitable castings. We liked the idea of rummaging around for vintage rectangular-port heads, or even good oval ports, but this desirable iron is getting difficult to find. Vintage big-port heads at bargain prices are rare, and we definitely planned on a full rebuild, along with serious grinding and port work, if we did score a set. Realistically, all of this scavenging and reworking comes at its own price, which starts to add up in time and money. Tally in the seat work, new guides, spring seat machining, new valves, seals, and all the rest, top it with the porting time and supplies for a full port and polish job, and the cost of those vintage castings escalates quickly, even if we could find them.
You might call us lazy, but we just gave up on the heroics of dirt-cheap ported stock iron, and ordered up a fresh set of replacement castings from Summit Racing. These heads feature 308cc rectangular ports, with 2.250-inch intake valves and 1.88-inch exhaust valves. More importantly, they are brand new and ready to run. With 330 to 355 cfm of intake flow, these cylinder heads will outflow any of the stock iron by a substantial margin. The Summit heads definitely save on time scrounging for the "good" OEM iron, and maybe even more time and money in trying to make them "better" with all the rebuilding and porting that's bound to follow.
With the addition of the Summit iron heads, we had our basics in place. To some, it might appear a fairly bare-bones effort-and it is. At this point, there was little to differentiate our engine from any rebuilt truck motor (other than a modest bump in piston spec, a hot cam, and replacement iron heads). Of course, there is the supporting cast of characters required to complete the transformation to a righteous high-performance powerplant. The cam needs support with accompanying parts-good pushrods, rockers, and springs for starters. Here, we upgraded with all of the required components straight out of the COMP catalog. Up top, our bare long-block needed a matching ensemble, and there are quite a few choices in inductions. We opted for Edelbrock's Performer RPM Air-Gap two-plane intake manifold, a reliable power-maker in applications to around 600 hp. A Mighty Demon 800 carb finished off the induction combination.
Number Crunching
With the basic nature of our .060-over 454 build, the assembly was not much more complex than wrenching together a stocker. All told, once dressed-up in a coat of Dupli-Color Chevy Orange paint, Dart cast-aluminum valve covers, and loaded on the dyno at Speed-O-Motive, our 454 had the looks of a solid hot street mill. Fired up and loping at an idle, the solid roller COMP cam definitely exhibited a noticeable thump, though the idle quality was far from outrageous. Thank the conservative cam timing for that. After the required warm-up and break-in period, the final hot valve-lash settings were confirmed and adjusted as required, and the base timing was set to a conservative 34 degrees. Next, dyno operator Jake Hairston methodically dialed-in the air/fuel ratio and we were ready to let the rpm roll for the numbers. Within minutes, we had the output quantified with 579 peak horsepower coming in at 6,200 rpm, and a stout 545 lb-ft of torque at 4,100 rpm.
This big-block certainly generated the torque these engines are known for, coming on hard right at the bottom of the pull, and cresting the 500 lb-ft mark by 3,000 rpm. That's 500 lb-ft right off the go with any reasonable street torque converter, and without a doubt, a full and fat torque curve like this is sure to provide axle-ripping, sideways street action when the hammer is dropped. We could have tuned in more power higher in the curve, in search of the added 21 hp that would give us 600hp bragging rights, and a single-plane or tall spacer and another couple of hundred extra cfm of carb capacity would likely have nudged the top-end power curve skyward. There would be a price to pay, though, in raw low-end torque. When it comes to a street application, torque rules the road. A sky-high induction would also foil any stock flat-hood plan, so we stuck with the lower rise intake and reaped its rewards in torque and stealth.
 A stock-replacement Melling...  A stock-replacement Melling oil pump covers the lubrication needs. The standard pump should provide plenty of lube to let the bearings live a long and healthy life. |
 After we installed the front...  After we installed the front cover, we thought better of it and checked the Buttoned back up with the cam dialed to 108-degree intake centerline, the PRW SFI-certified damper was installed. Leave the mallet in the toolbox, and always use the appropriate installation tool with a damper.cam timing. Sure enough, it was over-advanced. We then opened the cover to dial the cam to the straight-up position. |
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 COMP's EndureX solid roller...  COMP's EndureX solid roller lifters now come with forced-bearing oiling for improved durability in street applications. Install new lifters by following the manufacturer's procedure for cleaning and preliminary lubrication. |
 Though the Summit iron heads...  Though the Summit iron heads we selected come fully assembled, a spring upgrade is appropriate for use with the stout COMP solid roller. In no time, Oscar at Speed-O-Motive substituted a stiffer set of COMP springs (PN CCA-954-16). |
 We weren't about to dig all...  We weren't about to dig all over town for a set of OEM rectangular-port heads, then rebuild and port them. Our set of Summit replacement castings far outflow the stockers (see flow numbers in chart), and come ready to bolt on in most applications. |
 With the solid roller cam,...  With the solid roller cam, the right valvetrain is a must for longevity. We used a set of COMP aluminum roller rockers in a 1.7:1 ratio, and Manley 3/8-inch pushrods. The pushrod selection is important for proper geometry, and should be mocked-up on the engine. The roller tips should sweep the middle third of the valve tip, and this is about perfect. |
 With any solid cam, roller,...  With any solid cam, roller, or flat tappet, the lash must be set to specs during assembly; valve adjustment requirements are often overstated. Once set hot after break-in, the adjustment should hold for quite some time. This street roller takes a tight .018 inch on the intake and exhaust. |
Speed-O-Motive Crate Motor
We realize not everyone has the time or ability to build a 468ci big-block in their garage, in which case you might be interested to know that this exact engine can be ordered as a crate motor from Speed-O-Motive in West Covina, California. The entire package is $8,500, including dyno time. The only substitution is that Speed-O-Motive will use Dart Iron Eagle heads, which are identical to the Summit pieces in our story. (Dart builds and assembles the Summit heads, then engraves them with the Summit Racing logo. When spec'ing out headers, or anything else, use the Dart Iron Eagle guidesheet for the 308cc runner version.) As a point of reference, $8,500 is about the same as the street price for a GM ZZ502 crate motor, which makes 502 hp at 5,200 rpm. To find out more, call Speed-O-Motive at 626-869-0270.