We knew the cam would make hard-hitting torque, but questioned whether it would have the legs to run up the rpm range, which would be vital to making big horsepower upstairs. In fact, we questioned whether the 224 degrees of duration would allow the engine to make peak power anywhere near the 6,000-rpm range, an rpm capacity we know a 350-cube engine would require to make over 400 hp. When questioned, Vizard reassured us by stating confidently, "I've been speccing cams for well over 20 years, and haven't been wrong yet, but maybe I'm due." Complementing the cam, we increased the rocker ratio from the stock 1.5:1 to 1.6:1 with a set of COMP Magnum rockers, bumping the valve lift delivered by our cam from 0.528 to 0.563 inch in the process. The high lift delivered by this combination would be a big help in high-rpm power. We didn't skimp on valvesprings, since power production only continues as long as the valvetrain is under control. We used COMP's high-tech beehive springs, which significantly reduce valvetrain weight, and resist the onset of power-limiting valvespring surge. Prior testing had shown that the beehive springs extend the rpm potential of a hydraulic roller system.
With this, our engine's internals were essentially determined, and all that remained were the supporting parts. There was no misunderstanding that we needed an effective induction system with enough capacity to make power up top and a layout that would encourage torque as well. As a nod toward value, we went with a Professional Products Crosswind two-plane intake manifold. We know this intake manifold configuration delivers the best overall power from engines operating up to 6,500 rpm, and prior testing has shown the Professional Products' piece is a worthy unit. To top the manifold, we used a new Holley 3310 750-cfm vacuum-secondary carb, probably the most universal high-performance carburetor ever offered. With 350 cubes to feed, the 750 cfm offered by this carb looked like plenty to keep the engine happy up into the 6,000-rpm range, and it is very hard to beat this carburetor on the basis of airflow per dollar spent. With the addition of a Summit HEI distributor and MSD wires, we had our 350 combination established.
On The Dyno
Anticipation was pretty high on dyno day, as dyno operator Jake Hairston mounted our sweet-looking small-block to the DTS dyno at Speed-O-Motive. Very few engines we've put together have ever drawn such widely varied "guesstimates" regarding the power outputs. Running the numbers on a variety of engine simulation software programs showed output nearly all of us regarded as outrageously optimistic. As the crowd gathered for testing, jawbones were working overtime. We had doubters who maintained that 400 hp would be a stretch [including the author, Steve Dulcich-ed.], while a few in the group figured the engine would be a little stormer. Jake couldn't be engaged in giving an opinion, stating, "We'll be up and running in a few minutes, and I'm just going to wait and let the engine tell the story." With the timing dialed in at a conservative 32 degrees of total advance, the engine was fired and brought to life. Before long, a few stabs of the throttle were made to gauge the carb mixture, and the raw torque numbers looked encouraging. We caught a few numbers flashing well over 400 ft-lbs on the torquemeter-it looked like this thing would make some power.
Our first power runs came on really strong, building torque to 430 corrected ft-lbs, but the power went awry at higher rpms, basically nose-diving just before 5,000 rpm. (Power maxed out at 4,900 rpm with just 400.5 hp registered.) The peak torque rpm of about 4,500 rpm indicated this engine would really run the number upstairs if everything was right, predicting a peak power number somewhere in the vicinity of 6,000 rpm. If that held true, there was no doubt about eclipsing the 400hp barrier, in fact it would be substantially past that point. Jake quickly detected that the high-rpm miss was ignition related, and went to work replacing the HEI module with a high capacity four-pin Dyna-Mod unit from Performance Distributors. With that, the tension in the test cell was higher than ever as the engine was once again loaded against the dyno. The module definitely solved any ignition-related problem, as the engine screamed to the 6,400 rpm upper limit set at the control console, never missing a beat. The power kept coming as the 350 reached a peak at 6,200 rpm, running up the range with even more fury than we had hoped for. We had over 440 hp on the read-out! This combination just kept hanging on as the revs built, and with peak output at 6,200, it was not really surprising that the peak number was well above expectations. Interestingly, the Holley 3310 showed an ideal air/fuel ratio right out of the box. We never cracked open a float bowl for a jet change.
Dialing-in the ignition timing through a timing loop, we achieved a repeatable 447 peak horsepower at 6,200 rpm, and equally impressive torque at 445 ft-lbs. Our cheap 350 proves that outstanding output can be had on a budget. Did we just get lucky on this one? The real magic is in selecting the combination to work together and get the most from the each component. No doubt, our well-planned 350 nailed that requirement.
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