Block inspection Some visual checks Cylinder cracking Scuffing

Block inspection Crack detection • Bolt holes • Main bearing webs • Core plug holes • Intake valley

Block inspection Cylinder wear • Maximum wear 90 across piston pin, at top of cyl • Head bolts & coolant circulation distort cylinder • Taper – difference between bottom and most worn • Actual wear exceeds measured • Taper limit -. 008”

Block inspection Piston clearance • Don’t confuse taper with clearance • Minimum cylinder diameter – max piston diameter

Block inspection Checking pistons • Ring groove wear =. 003” to. 006” or 2 times new

Block inspection Checking pistons • Worn or collapsed piston skirts • Measure 90º across piston pin at top & bottom • Knurling – If clearance exceeds specs up to. 002”

Block inspection Checking pistons • Collapsed piston – When piston loses cam shape • Measure 45º across piston pin • Leads to piston ‘slap’

Block inspection Checking piston pin clearance • Oscillating pins are checked by feel • Full floating pins can be disassembled & measured • . 0002” clearance in pistons • . 0004” clearance in rods

Block inspection Checking block flatness • Scrape deck surface • Deburr deck surface • . 004” Go/No-go • Consider head flatness

Block inspection Measuring main housing bores • Main caps stretch from load • Check block for warpage

Block inspection Measuring main housing bores • Check bearing wear • Bent crankshaft – Wear all around bearing • Warped crankcase – Wear on one side only • Concentricity of main seal

Block inspection Measuring main housing bores • Clean & deburr parting faces • Check fit in saddle • Torque & measure with dial bore gauge

Block inspection Checking the crankshaft • Scoring • Taper & out of round • Taper exceeding. 0005” may allow oil to escape

Block inspection Crankshaft straightness • Use V-blocks or end main bearings • Should not exceed ½ main clearance

Block inspection Crankshaft cracks • “Ring” crankshaft • Wet Magnaflux crankshaft

Block inspection Connecting rod bores • Stretch comes from engine load • High engine speeds tend to stretch bores • Small displacement engines use large rod bores • Caps may spring outward on disassembly • Bend & twist should be within. 001” per 6” of rod. Cause wear patterns on pistons & bearings