April '17

Issue link:

Contents of this Issue


Page 48 of 87

APRIL 2017 PRECISION ENGINE 13 PRECISION ENGINE bore, using the skirts to square the piston in the bore. With the base of the compressor tool firmly held against the block deck, push and/or lightly tap against the piston dome until the piston dome is roughly flush to the deck. When inserting the piston through the ring compressor, make sure that the bottom of the compressor remains flat and flush with the block deck. If you feel a dead stop, that means that a ring has expanded out between the bottom of the compressor and the block deck, so stop. Pull the piston back up, re-fit the piston to the compressor and try again. When the compressor is adjusted prop- erly, you should be able to either push the piston into the bore with your fist, or with a gentle tapping on the piston dome with a clean plastic hammer. If it argues with you, don't force it. Re-examine and try again. If you trap a ring onto the block deck and try to force it, you can easily bend or break a ring. While inserting the piston and rod package, keep an eye on the orientation of the rod big end to make sure that it's in line with the rod journal. Avoid cocking the assembly, as the rod big end can snag onto a crank counterweight. Once the top ring enters the cylinder bore, the compressor can be removed. With one hand on the rod big end to guide it, push or tap the piston down until the rod big end bearing makes light contact with the rod journal. Keep an eye on the rod big end as it approaches the rod journal to avoid the rod big end saddle edges from nicking the crank's rod journal. Install the rod cap and bolts, and tighten the rod bolts to specification (using torque only or torque-plus-angle; or by tightening as you monitor rod bolt stretch, depending on the application). After each piston and rod assembly has been installed, rotate the crank with a beam-type torque wrench and note how much force was required to rotate the crank. Do this after each cylinder is filled. If you encounter a cylinder location where excess rotational force is required, this can be a sign that something is wrong (ring slipped/distorted, insufficient rod bearing clearance, rod contacting the block, etc.). Using a V-8 engine as an example, once all eight rods and pistons have been installed, you should be able to rotate the crank with no more than about 25 foot- pounds or so. MIKE MAVRIGIAN owns and operates Birchwood Automotive in Creston, Ohio, where he builds custom engines, street rods and performs vehicle res- torations. He has written thou- sands 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 Visit Birchwood's website at www.birchwoodauto- - Billet or forged pistons - Several proprietary coatings available - Full round and modern strutted forgings available - Lightweight 3D crown and undercrown milling available 7 2 0 1 I n D u S t r I a L Pa r k B Lv D . Mentor, oH 44060 • 800.321.1364 Call today and step up your engine program! 1-800-321-1364 Custom pistons optimiZed For your engine! proud supporter oF drag raCing serVing tHe raCing industry For 75 YEARS!

Articles in this issue

Links on this page

view archives of THE SHOP - April '17