THE SHOP

July '20

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JULY 2020 THE SHOP 65 PRECISION ENGINE tolerance range of a mere 0.7 gram, and our ICON pistons revealed a range of only 0.2 gram. Keep in mind that 1 gram is equal to the weight of a single U.S. currency bill. While no machining corrections were needed, the rods and pistons were matched and labeled in order to compensate for these small differences, mating lighter pistons to the heavier rods, resulting in a close-to-zero tolerance for these matched components. In this balance job, bobweights were set at 852.5 grams. Due to the light weight of our pistons and the weight-relieved SCAT crank, Holtrey was forced to add two small slugs of tungsten into the front and rear counterweights, with a 28-gram slug in the front counterweight and a 20-gram slug in the rear. Our final crank bal- ance result was -0.9 gram front and -0.5 gram rear, which is within the ideal range. Next time we'll address the cam and bearings, bearing clearance, the belt drive and more. MIKE MAVRIGIAN owns and operates Birchwood Automo- tive in Creston, Ohio, where he builds custom engines and street rods, and performs vehicle restorations. He has written thousands of technical articles, as well as nine books on automotive technology during the past 30 years. Mike can be reached at (330) 435-6347 or birchwdag@ frontier.com. Visit Birchwood's website at www.birchwoodautomotive.com. Our example balance job weights were recorded as follows (in grams): Rod big end 429 Rod small end 186 Rod bearings (for one piston) 86 Piston 406 Piston pin 117 Piston pin locks (for one piston) 3 Rings and rail 41 Total 1,697 ½ total 848.5 +4g oil cling 852.5 When final-installed with all bearings and main caps torqued, our crank end play measured 0.006 inch. 800.264.9472 • DesignEngineering.com • BLOCKS EXHAUST AND ENGINE HEAT • BLOCKS EXHAUST AND ENGINE HEAT • USE ON TRANS TUNNELS F,IREWALLS, • USE ON TRANS TUNNELS F,IREWALLS, FLOORS, ABOVE EXHAUSTS & MORE FLOORS, ABOVE EXHAUSTS & MORE • AGGRESSIVE ADHESIVE BACKING • AGGRESSIVE ADHESIVE BACKING • BLOCKS EXHAUST AND ENGINE HEAT • USE ON TRANS TUNNELS, FIREWALLS, FLOORS, ABOVE EXHAUSTS & MORE • AGGRESSIVE ADHESIVE BACKING DEALER & DISTRIBUTOR INQUIRIES WELCOME BLACK IS COOL! BLACK IS COOL! BLACK FLOOR & BLACK FLOOR & TUNNEL SHIELD TUNNEL SHIELD EXTREME HEAT BARRIER EXTREME HEAT BARRIER BLACK IS COOL! BLACK FLOOR & TUNNEL SHIELD EXTREME HEAT BARRIER

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