Chevy Small Block Build - Mildly Amusing

How to build a recession-proof 365 hp small-block.

Richard Holdener Oct 1, 2012 0 Comment(s)
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To our surprise, the cast crank was still standard and in excellent shape. We took the liberty of micro polishing the crank just to make ourselves feel better, but it was actually good to go as it came from the wrecking yard. The forged pistons were used in conjunction with a set of used LT-1 pink rods L&R had laying around. Reusing the stock rods can save a few bucks, but we liked having the pink rods for future bench racing sessions. The aftermarket is full of relatively inexpensive forged rods, but our sub-6,000 rpm motor required no such hardware. We did pop for a new harmonic balancer, as the high-mileage unit looked ready to give up the ghost at any moment.

With our short-block assembled, it was time to turn our attention to the power portion of the build up. While a quality short-block is important, the cylinder heads, valvetrain, and induction system are really the determining factors in terms of eventual power output.

First on the list was a suitable camshaft. Since this motor was intended for daily street use, we wanted to avoid any radical cam grinds. Chevy put a ton of duration in its factory performance cams in the '60s, something that inevitably hurt drivability. We erred on the conservative side in terms of cam profile, choosing a mild PowerMax hydraulic flat-tappet piece from Crane Cams. The dual-pattern, emission-legal cam offered a 0.427/0.454 lift split, 204/216-degree duration split (at 0.050), all ground on a 110-degree lobe separation angle. Crane also supplied the necessary hydraulic lifters. Again, note the mild hydraulic cam was a far cry from the solid/mechanical cam run in the original 327. The hydraulic cam made valve adjustment a set-it-and-forget-it proposition.

Next on the to-do list were the cylinder heads. Though a number of great cylinder heads (factory and aftermarket) exist for the small-block, we stuck with the stock castings. Producing 365 hp using a set of aftermarket heads is a walk in the park, but doing so with stock (albeit ported) hardware is much more impressive, not to mention cost effective. L&R Automotive was also responsible for the head work, including porting and installation of the larger 2.02/1.60 stainless steel valves (from S.I.). According to the flow bench, the porting and oversized valves freed up an additional 30-35 cfm per runner. The extra head flow allowed our small-block to take full advantage of the extra lift offered by the Crane cam. Naturally, the 882 heads received a suitable valvespring package to work with the revised cam specs. The stock springs were long since worn out, and inadequate even when new. L&R also set up the heads to accept screw-in rocker studs and guide plates, as factory press-in rocker studs have a tendency to pull out with increased spring pressure. Cost for this would be $725 retail.

The change allowed use of a set of non-self aligning Crane 1.5 ratio roller rockers. It is possible to retain the stock stamped-steel rockers, but given the slightly higher engine speed (over stock) of this new combination, we wanted the extra insurance and valvetrain stability offered by the roller rockers.

With our long-block basically finished, the 350 was missing only the induction, exhaust, and ignition system. When it comes to street motors, forget all about the trick single-plane and tunnel ram intakes. If you want a broad, usable torque curve with plenty of top-end power, stick to a good dual-plane intake. For our 350, we chose an Edelbrock Performer RPM Air-Gap intake. The RPM version offers superior flow compared to a traditional Performer, while the air gap feature theoretically allows for airflow to help cool the individual runners. This cooling feature is even more important once the motor is installed in a vehicle. The RPM intake was topped off with a Demon Fuel Systems 650 Street Demon carburetor. A similar size Holley Street Avenger or even a big Q-jet (or Edelbrock equivalent) would likely work just as well on this combo.




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