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Block inspection

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.

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Block inspection

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

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

  3. 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”

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

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

  6. 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”

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

  8. 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

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

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

  11. 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

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

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

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

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

  16. 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

  17. Block inspection • Connecting rod bores • Special gauges are used for housing bores • Out of round & size must be checked

  18. Block inspection • Connecting rod failures • Begin with bearing failure • Bearing shell wedges under the other • Rod bolt breaks • Rod & cap break

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