Small-Bore Pontiac Engine Build - Revenge Of The 350
At 3.875-inches, the 350 has one of the smallest bore diameters in the Pontiac engine family. Only the '55 287 (3.750) and '63-'67 326 (3.719) are smaller. Though the stroker crank gains the real inches, a 0.030 clean-up was performed. The pen points to factory-issue valve relief chamfers atop the 350's bores. On this 1973 casting, the chamfers are adjacent to the exhaust valves only. Later 350 block castings have them facing both valves. These chamfers help unshroud the valve heads for improved breathing, but also add combustion chamber volume for reduced compression ratio. A little known fact is that camshaft lifts over 0.650-inch will send the valve heads smashing into the bores on 287, 326 and 350 blocks, unless radical chamfering is performed. Our 0.549/0.573 lift hydraulic roller will be safe, however. | 
The key ingredient in this 383 recipe is Tomahawk's new cast nodular iron stroker crank. It features 3.00-inch mains, 2.200-inch (big-block Chevy size) rod journals, and a 4.00-inch stroke. It can be purchased separately for $325, and there's even an optional version with 2.225 rod journals that'll turn a 400 into a 428. | 
Despite its low price, the Tomahawk crank features chamfered oil holes and fully-radiused rod journals. | 
Revco Balancing handles the balancing work on all Tomahawk stroker kits. The fully welded "no holes" internal balance job leaves no voids in the counterweights to catch oil and stir up windage. The bob weight is 1,979.3 grams. photo by dave anderson. | 
The pen points to an improved thrust bearing by King Bearing. Available as part of main bearing set MB5511AM, it features notched interfaces between the upper and lower halves that collect oil and enhance lubrication. Until now, Pontiac builders had to cut the notches into stock-type thrust bearings (left). The upper halves of the main bearing shells are grooved, the bottoms are smooth. Ken says that fully-grooved main bearings are best left to full race applications, as they can reduce low speed oil pressure in stop and go traffic. | 
Unlike many aftermarket stroker kits for Pontiac, the Tomahawk kit requires absolutely no block clearance work. The pen points out a classic trouble spot that has plenty of clearance, thanks to the crank's compact counterweight design. Notice the ARP main studs. They're stock sized (7/16, 1/2-inch at rear) but offer nearly twice the clamping force of stock bolts. | 
Also included in the $1,595.95 kit price are full-floating 0.990 pins, double spiral locks, bronze bushed 6.8-inch 4340 forged steel I-beam rods and forged Probe full-skirt SRS (Sportsman Racer Series) pistons. The rods weigh 756 grams and are among the lightest 4340 rods currently on the market, while the pistons are equally svelte at 539.5 grams, including pins. Remember when stuff like this was reserved for NASCAR? | 
Installed, the pistons yield a zero deck height with plenty of valve relief volume. The rings are 1/16 - 1/16 moly filled with a 3/16 oil pack. End gaps are set at 0.018 top, 0.021 second. | 
Cutting parasitic drag is the same as adding power, so an Ishihara-Johnson Zero-Tolerance Teflon crank scraper is used. With this innovative design, there is zero clearance between the crank and the scraper. Sold as a kit, several hours are required for precise fitment, but Ken feels the result is well worth the effort. |
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