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Chevy 427 Short-Block - Huffer Overhaul Part III

Making Race Gas Power On A Pump Gas Budget

By Andrew Schear

Any engine builder will tell you that the key to making gobs of power is using the correct combination of components. In other words, using a .700-inch lift cam in an 8.5:1 compression small-block with GM 1.94-inch, 1.50-inch iron heads just doesn't make sense. Nevertheless, some builders think more cam means more power. We're here to tell you that even without tons of cubes you can make great power if you use the correct parts for your application.

As a quick refresher course, we left you folks at the machine shop where our Huffer powerplant received freshly machined surfaces, a full engine balancing, and all the necessary details in preparation for assembly.

Project "Huffer" as we've come to call it was designed off of a very common short-block, the 427 Chevrolet; an engine that GM made for many years and is very accessible in the used marketplace. As any avid 427 enthusiast will tell you, the 427 loves rpm which we found was one of the keys to making horsepower with less displacement.

When we began our huffer overhaul we started with a blank piece of paper and asked ourselves what we hoped to accomplish on the dyno. We determined that 700 hp on pump gas and 800 hp on race gas sounded like respectable numbers from 427 inches. At that point we were left with the details of how to make the magic happen with off-the-shelf parts. Since we already had the 427 crank, block, and Merlin heads, we thought that a 7.9:1 compression ratio was perfectly attainable with flat-top pistons and 120cc combustion chambers. The cam choice no doubt left us with the biggest questions. Since most supercharged engines move the powerband down slightly on the rpm table we chose a cam that ordinarily would have been large for a 427, but we figured that 11-13 pounds of boost would be just right. Our Lunati solid roller (50231 LUN), while listed as a drag race cam, had the perfect specs for our blown 427. Valve lift was .680 inches on the intake side and .700 inches on the exhaust, while duration at .050 inches was 258 degrees on intake and 268 degrees on exhaust. Our choice was actually made much easier by the Lunati guide specs provided by their online catalogue. If you're not quite sure what cam specs are best for your engine, it's best to give the tech support a call, they'll probably have the answer you're looking for.

Knowing that boost retard technology was available, we chose to retire the old Vertex magneto in lieu of an MSD 6BTM electronic ignition combined with an electronic boost retard module. While the magneto is great in race applications, the ability to retard timing in situations where detonation may be present is invaluable.

Carburetion is yet one more example where less is more. We often find over carburetion in blown applications. While unsure whether the difference would be significant, we brought our Holley Dominator 1050s as well as a set of HP950 blower carbs with us on dyno day. As we suspected, the smaller carburetors actually produced 12 hp more than the dominators! We have only two words to say, POWER VALVE!

As a general rule when a big-block is going to spend time above 7,000 rpm, it's wise to take a few precautions. So when it came to valvetrain, we opted for a rocker stud girdle to keep things in place. We also used ARP fasteners as opposed to the fasteners traditionally found in an OEM assembly.

When our Huffer was finally assembled, we were off to Vrbancic Brothers Racing and their accurate DTS dyno to see if our combination of speed parts was indeed a winning combination. Unfortunately we found some slight leakage from the water passages on both cylinder heads. So, without a single dyno pull for the day we were back to the drawing board for a little exploratory surgery.

By Andrew Schear
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