THE SHOP

Performance & Hotrod Business - January '15

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6 n PRECISION ENGINE n January 2015 interlocking, ductile iron valve seats and premium one-piece stainless steel high- flow 2.140-inch intake and 1.810-inch exhaust valves. Heat-treated, machined steel retainers and valve locks with heavy- duty valve springs accommodate valve lifts up to 0.600 inches. The exhaust flange has been extended out 0.125 inches in order to provide dry exhaust bolt/stud holes. Exhaust bolt holes feature helical thread inserts for added strength and durability. While I test-fitted both the Edelbrock dation specifies a three-step process start- ing with 40 foot-pounds, followed by 55 foot-pounds, then 70 foot-pounds. I fol- lowed my preferred four-step tightening, starting at 25 foot-pounds, followed by 40 foot-pounds, followed by 55 foot-pounds, with final tightening at 70 foot-pounds. The polished ARP stainless 12-point bolts provide a beautiful finished appear- ance that will complement any build. The tightening sequence specified by Edelbrock was followed. Pushrods We used custom 3/8-inch chromoly pushrods from Trend at a length of 8.318 inches (from cup seat to tip), a wall thick- ness of 0.080 inches, and cup and tip diameters of 5/16-inch. During measur- ing, I used one of my adjustable checking pushrods, with cam lobes on their base circles and with the rocker arm adjusters set at a distance of 0.370 inches from the bottom of the rocker arm to the rocker's adjuster ball. I then added 0.050 inches preload for the hydraulic lifters. With the checking pushrod removed, I placed a 5/16-inch ball in the cup of the checking pushrod and measured overall length, then deducted the 5/16-inch ball diameter (which actually measured 0.312 inches) to obtain the final BOC (bottom of cup) length. Because it's difficult to measure from the base of the pushrod cup, using the 5/16-inch ball allows you to obtain an accurate measurement. Again, measure overall length of the checking pushrod from the ball to the tip, then deduct the diameter of the ball. In our application, the overall length of our checking pushrod (with temporary ball placed in the upper cup) measured 8.590 inches. Subtracting the 0.312-inch ball diameter resulted in a desired BOC length of 8.318 inches. Rocker Arm System Our rocker arm system is comprised of a pair of Mopar Performance rocker shafts and Mopar Performance billet hold-downs, (five hold-downs per head, all sourced from Summit Racing), and a set of Crane aluminum full-roller rockers Our rocker system features a set of Crane full- roller rockers and Mopar Performance rocker shafts and aluminum shaft hold-down kit. Pay attention when installing the rocker shafts. The small oil holes must face downward. Also note that the oil holes are slightly offset in relation to the rocker bolt holes. The oil holes must be biased toward the valves. PRECISION ENGINE Crane's roller rocker set includes forged aluminum bodies, heavy-duty roller bearings, and efficient oiling passages to feed shaft pivot, pushrod and valve tip areas. Hardened ball-tip adjusters and adjuster nuts are included. A set of Crane 0.015-inch shims were used to obtain proper rocker arm side clearance. Rocker side clearance should be in the range of 0.015 inches. While all of the Crane rockers matched in terms of width, the variables included slightly unequal width of the rocker shaft hold- down blocks. In combination with the use of our spacer shims and experimenting with hold-down block location, our setup averaged 0.015 inches of side clearance at all rocker locations. It's a tedious process, so plenty of patience is required in terms of measuring each piece, test-fitting, measuring, recording the results, disassembly, re-shimming, re-assembly, etc. The final results were great, but it took a while. and Mopar Performance heads, I opted to go with the Edelbrock heads for final assembly and dyno run. Head chamber to piston clearance (without head gasket in place) was mea- sured at 0.035 inches at the upper quench area. Factoring in the MLS head gasket thickness of 0.040 inches, this provides a piston-to-head chamber clearance of 0.075 inches. Valve-to-piston clearance (again, without head gasket) measured a healthy 0.250 inches at the intake and 0.270 inches at the exhaust valve locations. Our cylinder head gaskets are the MLS (multi-layer steel) type, from Cometic. These feature a gasket bore of 4.500 inches and an installed thickness of 0.040 inches, (Cometic P/N CGT-C5464-040). In order to secure the heads to the block, I chose ARP's 12-point polished stainless steel head bolt kit, P/N 445-3706. These are 7/16-inch diameter, high tensile strength stainless bolts with an 180,000- psi rating. I applied ARP Ultra Torque Fastener Lubricant to all bolt threads, and to each side of each flat washer and to the underside of each bolt head. (Note: When installing washers to the bolts, note that one side of the washers feature a slight chamfer. This chamfer side must face the underside of the bolt head, in order to insure clearance to the radius on the underside of the bolt head.) Each bolt was tightened, in sequence, in multiple steps. Edelbrock's recommen-

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