October '19

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OCTOBER 2019 THE SHOP 41 PRECISION ENGINE The ARP 2000 7/16 x 1.600 inch rod bolts are specified by SCAT at 70 foot-pounds, with a maximum allowable stretch of 0.0062 inches. Each rod bolt was indexed at zero on my rod bolt stretch gauge. During initial tightening (with ARP lube on bolts), the bolts stretched 0.0035 inches at 40 foot-pounds, and at 0.0045 inches at the final (specified) 70 foot-pounds of torque. Using my adjustable tapered Summit ring compressor adjusted to 4.130 inches, the pistons entered their bores with a firm push of the fist, avoiding the need to tap with a piston hammer. Once the pistons were below deck, how- ever, I took advantage of my Goodson extended-nose piston hammer to gently nudge each piston down for rod big end bearing contact with the crank pins. The plastic long-nose piston hammer is handy, eliminating the need to stretch my right arm to push the piston down while guiding the rod onto the crank. Rod side spacing was again verified during final assembly at a consistent 0.018 inches. With all eight pistons installed, ini- tial crank rotation required 23 foot-pounds of effort. (Note: In Part I of this build, I made a boo-boo. A typo that I made noted that the raw cylinder bores were 4.136 inches, which was obviously incorrect. The raw bores were actually 4.116 inches, which were then bored to 4.126 inches and final- honed to 4.131 inches. Sorry about that. Sometimes I'm a lousy typist!) VALLEY PLATE & OIL PRESSURE SENDER OEM valley plates are just plain ugly. An excellent option (aside from fabricating one from scratch) is Holley's new billet alu- minum valley plate that features a trussed-X upper surface and a threaded bung up front that accepts an oil fill cap (P/N 241-362). In lieu of using a fill cap, I opted to take advantage of this bung to install a valley breather, using an aluminum threaded breather tube from CFM along with a K&N breather P/N 62-1450. This provides direct crankcase breathing at the lifter valley. The threaded tube fitting is designed for Holley's thread size and directly screws into the valley plate bung (same thread size as Holley's fill cap for its valve cover). Since the custom Holley valley plate does not feature a hole for the oil pressure sender (as is common for many aftermarket valley plates), I drilled a 5/16-inch hole in the plate that aligns with the Dart block's oil pres- sure hole, and installed an aluminum base adapter from ICT. This adapter shares two of the 8mm valley plate holes for attachment, and offers a 16mm x 1.5 female thread, and seals to the valley cover with an O-ring. This threaded hole will accept a 16mm x 1.5 OE-style oil pressure sensor. However, in order to have the option of using an aftermarket pressure sender, I installed an Earl's adapter (16mm x 1.5 male thread to 1/8-inch NPT female thread) to the ICT adapter (this requires a 16mm crush washer between the base adapter and fitting). This allows installation of any after- market sender that features a 1/8-inch NPT male thread. The only challenge was to obtain a proper O-ring seal between the valley plate and the ICT adapter, since the top of the valley plate features a trussed X-pattern, which creates a 0.050-inch relief in the adapter's O-ring area and the surfaces where the adapter mates to the valley plate. The fix: to mill 0.050 inches off of the bottom of the ICT adapter, leaving about 1/16-inch of material around the O-ring location. This allows the adapter to mount

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