October '18

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46 THE SHOP OCTOBER 2018 OCTOBER 2018 Engine Build, Part IV p.46 JFC Racing Profile p. 52 Engine Products p.56 PRECISION ENGINE Building a 632 Mountain Motor Part IV – Working on the pushrods, torque specs & fuel pump. By Mike Mavrigian EDITOR'S NOTE: This is the fourth installment in a multi-part series following the build of a 632-ci big-block drag racing engine. See Part I in the January 2018 issue of THE SHOP, Part II in the April 2018 issue and Part III in the October 2018 issue. PUSHROD CHECKING, ORDERING Each pushrod length location was checked as follows: Rotate the camshaft to place the lifter onto the lobe base circle. Install the Here's a view of all rockers installed on the right-side head. checking pushrod (Jesel supplies a multi- piece checker). With the rocker arm adjuster turned one full turn out from the seated position, adjust the checking pushrod to obtain desired lash (in our case, I used a cold lash of 0.020 inches for intakes and 0.022 inches for exhaust. Granted, since hot lash is 0.020/0.022 inches, and anticipated head growth under temperature will cause the heads to grow, I could have used about 0.014 inches cold intake and cold 0.016-inch lash. I decided to keep a bit of lash leeway for adjustment). Remove the checking pushrod and mea- sure total length. The rocker arm adjuster may be adjusted from one-half to two turns out. Jesel warns against operating its rocker arms with the adjuster positioned more than two turns out from the seat. Note: Jesel's pushrod checker consists of three 3/8-inch-diameter aluminum rods that screw together. The shortest piece mea- sures 1.502 inches, the next longest mea- sures 3.00 inches and the longest measures 5.00 inches. Each adjuster tip, from base of the hex to ball tip, measures 0.530 inches.

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