The phones rang off the hook when we covered the components and dyno testing of the low-buck 454 from Demon Engines in the Oct. '10 issue. Checking in at $2,650 outright (minus carburetor), the low-buck 454 from Demon Engines offered an attractive combination of power and pricing. Bypassing the stock replacement and wrecking yard motors, the mill offered a minimum of 400 hp for just less than three large outright and required no core exchange. Even more impressive was the fact that the 400 hp came with a peak torque reading of 542 lb-ft. In fact, torque production exceeded 500 lb-ft from 2,800 rpm to 4,600 rpm, making this big-block a real thumper and ideal for a variety of different applications, including a performance street machine, a truck, or even an RV. Despite all this motor had going for it, we couldn't help but wonder what it might be like with a few performance upgrades. According to Demon Engines, even with a cast crank and factory rods with a bolt upgrade, the short-block will withstand considerable punishment. No way, you say? Not without a steel crank and forged rods! Check out part three when we add a low-buck turbo kit to the mix-but for now we will concentrate on upgrading the low-bucker with a few simple bolt-ons.
As much as we liked the Demon low-buck 454, we couldn't wait to perform a few upgrades, including new heads, cam, and 1.7-ratio aluminum roller rockers. Westech's Ernie Mena jumped in to adjust the valves during our dyno session.
The three most important power producers in any combination are the heads, cam, and intake. A close examination of this engine reveals that upgrading at least two of these components will yield significant dividends. Since it was already blessed with a dual-plane intake from Procomp, we set our sights on replacing the peanut-port heads and mild Xtreme Energy cam. As it turned out, our choice of cylinder heads required replacement of the Procomp intake, but more on that later. First up was the camshaft. Out came the XE268H cam from Comp Cams to make room for a slightly wilder XE284H. Our hope was that the new cam profile would shift the torque curve higher in the rev range, thus producing more peak power. At the same time, we couldn't help but hope that the gains would result in only minimal trade-off in low-speed power.
The original 454 from Demon Engines featured a static compression of 9.4:1, peanut-port heads, and a mild hydraulic flat-tappet cam. The combination was good for 445 hp and 542 lb-ft.
When it comes to cylinder heads, just about any performance aftermarket head represented a significant step up in flow and power potential compared with the factory truck heads. Ideally suited to the 400 to 450hp level, the peanut-port heads are a significant restriction. They were replaced with a set of Profiler heads from Dr. J's Performance. The Profiler heads offered a number of important upgrades, including lightweight aluminum construction and a significant increase in airflow. Lifting a set of iron big-block heads is no picnic, so it should come as no surprise that replacing them with their aluminum counterparts offers a serious weight reduction. On the all-important power-to-weight scale, less weight is the same as more power. Thus, replacing the iron with aluminum heads offers a power gain irrespective of the additional airflow. Naturally, we did not choose the Profiler heads on weight alone; we were much more interested in their impressive flow figures. The Profiler heads also feature a five-angle valve job, a 5/8-inch-thick deck surface, and 0.250-inch raised exhaust ports. They came with CNC combustion chambers and a valvespring package designed for our sub 0.600-lift hydraulic flat-tappet cam, all for less than $2,000.
Though more than adequate for the 400 to 450hp range, our three-tiered power package included removing and replacing the peanut-port heads.
The Profiler heads were unique in that the 290cc intake ports featured neither a traditional rectangular nor an oval-port shape, but a combination best described as "roval." The intake ports were essentially the size of a performance-oriented rectangular port with the corners rounded to improve flow. For a given area, a round port flows better than a square (or rectangular) one. The port shape required replacing the dual-plane intake from Procomp with an Edelbrock RPM Air-Gap. The Air-Gap was similar in design but featured ports designed for rectangular-port, big-block heads. These offered the best match for the ports in the Profiler heads. Ideally, the heads and intake can be port-matched, but we decided to run them as is to illustrate the combination used by most enthusiasts.
Since the motor had been previously broken in and run, we elected to replace the conventional oil with 5W-30 synthetic from Lucas Oil. Given the new cam, we also took the liberty of adding a quart of high-zinc engine oil additive.
The new heads, cam, and intake were run with a Holley 950 HP carburetor, which flows more air than the 750 HP run on the original low-buck 454. Despite the moniker, the 950 HP is actually a 750 body with an 850 baseplate. The combination actually flowed less than a standard 850 but works well on a variety of different (milder or smaller) engine combinations that might not work well with the larger 850 carburetor. The two final changes included upgrading pushrods and stamped-steel rockers originally supplied on the engine. The pushrods were not actually a necessity, as the 3/8-inch pushrods shared the 8.250/9.250 lengths with the 5/16-inch pushrods, but make sure to specify the proper guideplates when ordering the heads.
The HEI distributor and plug wires from Procomp were retained. With the right curve, we see no reason why the combination wouldn't run on 87-octane.
It is obviously possible to install a wild solid roller cam and even mill the heads to up the static compression ratio if you desire more power, but with this engine we were looking for a combination of daily driver and weekend warrior-something that could easily pull double duty without costing a fortune in fuel and still post some respectable e.t. and trap speeds in a suitable Camaro or Chevelle. The combination of aluminum heads and 9.4:1 compression meant the motor was plenty happy on 91-octane pump gas and could even be run on 87-octane with the right timing curve.
Run with a set of 2.25-inch dyno headers and a Meziere electric water pump, the modified 454 produced peak numbers of 464 hp and 542 lb-ft. The mods improved power by 119 hp, effectively transforming our low-bucker into something a bit more serious.
Run with Lucas 5W-30 synthetic oil, a set of 2.25-inch headers, and a Meziere electric water pump, the modified 454 produced 564 hp at 6,100 rpm and 542 lb-ft at 4,500 rpm. This represented a gain of 119 hp over the previous combination. Note that the peak torque value was unchanged, but it was moved higher in the rev range. Idle vacuum changed by 1.7 inches, and this combination might like a converter with a slightly higher stall for optimum performance. But the upgrade does illustrate that the Demon engine is a solid foundation for a performance buildup. Check back with us next month to see how well the cast crank and stock rods stand up to even more power as we add a homemade, low-buck turbo kit.
Dyno Results
Replacing the heads, cam and intake on the Demon low-buck 454 resulted in some serious power. Where the original low-buck combination offered peak numbers of 445 hp and 542 lb-ft, adding the aluminum Profiler heads, XE284H cam, and Edelbrock intake upped the peak numbers to 564 hp and 542 lb-ft. Even more power is available with wilder cam timing and/or more compression, but the increased cam duration would sacrifice low-speed power, mileage, and throttle response. The big-block offered more than 500 lb-ft of torque from 3,500 rpm to 5,800 rpm. Had we loaded the modified combination lower than 3,500 rpm, the torque production would have exceeded 500 lb-ft well below that engine speed, possibly as low as 2,800 rpm. That, my friends, is one impressively broad torque curve. Is it any wonder enthusiasts choose big-blocks?
AIRFLOW DATA: DR. J'S BBC PROFILE HEADS FLOWED WITH 4.30 BORE LIFT INTAKE EXHAUST 0.100 84 69 0.200 165 117 0.300 236 160 0.400 295 194 0.500 335 225 0.600 356 251 0.700 368 268 PARTS DESCRIPTION PN SOURCE PRICE Dr. J's BBC Profiler heads 19201992 Dr. J's $1,995.00 Fel-Pro 1017 head gaskets 375-1017-1 Jegs 83.98 Edelbrock Performer RPM Air-Gap intake manifold EDL-7562 Summit Racing 259.95 Comp Cams XE284-H CCA-11-250-3 Summit Racing 112.95 Comp Cams pushrods CCA-812-16 Summit Racing 72.95 Comp Cams pushrods CCA-7854-16 Summit Racing 37.75 ARP head studs ARP135-4001 Summit Racing 154.48 Comp Cams 1.7 rockers CCA-1021-16 Summit Racing 299.95 Total $3,017.01
