Transcript Block inspection Some visual checks • Cylinder cracking • Scuffing & scoring • Damaged fasteners • Housing bores Copyright 2003 Gary Lewis – Dave Capitolo.

Block inspection
Some visual checks
• Cylinder cracking
• Scuffing & scoring
• Damaged fasteners
• Housing bores
Copyright 2003 Gary Lewis – Dave Capitolo
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
Block inspection
Connecting rod bores
• Special gauges are used for housing bores
• Out of round & size must be checked
Block inspection
Connecting rod failures
• Begin with bearing failure
• Bearing shell wedges under the other
• Rod bolt breaks
• Rod & cap break