pollyp
Club Member
tday i measured the bores of the forged engine just to double check.
previously measured the forged pistons to have the widest diameter of 71.4mm
JE guideline says bores measuring 2.5 - 3.625" (63.5 - 92.075mm) need a minimum piston to bore clearance of 0.003 - 0.0036" (0.0762 - 0.0914mm)
measured the bores and plotted on a radar graph to visualise any variations.
cylinder 1: round n tight at TDC, bowls out at MDC then ovals slightly at BDC near the main bearings. the tightest point is 71.493mm at TDC (clearance of 0.093mm, just above minimum)
cylinder 2: slight ovality laterally, again starts tighter at TDC, bowls out MDC but ovals slightly at BDC. tightest point is 71.496mm (clearance of 0.096mm)
cylinder 3: nice even n round, same bowling pattern. bore is 71.506mm (clearance of 0.106mm)
cylinder 4: round n tight at TDC, bowls out abit at MDC but then ovals longitudinally at the bottom near the main bearings like cyl 1. tightest point is 71.498mm (clearance of 0.098mm above minimum)
also updated the "before machining" bore measurement graphs on post #3259
previously measured the forged pistons to have the widest diameter of 71.4mm
JE guideline says bores measuring 2.5 - 3.625" (63.5 - 92.075mm) need a minimum piston to bore clearance of 0.003 - 0.0036" (0.0762 - 0.0914mm)
measured the bores and plotted on a radar graph to visualise any variations.
cylinder 1: round n tight at TDC, bowls out at MDC then ovals slightly at BDC near the main bearings. the tightest point is 71.493mm at TDC (clearance of 0.093mm, just above minimum)
cylinder 2: slight ovality laterally, again starts tighter at TDC, bowls out MDC but ovals slightly at BDC. tightest point is 71.496mm (clearance of 0.096mm)
cylinder 3: nice even n round, same bowling pattern. bore is 71.506mm (clearance of 0.106mm)
cylinder 4: round n tight at TDC, bowls out abit at MDC but then ovals longitudinally at the bottom near the main bearings like cyl 1. tightest point is 71.498mm (clearance of 0.098mm above minimum)
also updated the "before machining" bore measurement graphs on post #3259
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