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How to use plastigage

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#1 Whiplash



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Posted 07 April 2008 - 09:57 AM

PLASTIGAGE was designed as a final check of total vertical oil clearance during reassembly. It was not meant as a replacement for properly measuring crankshaft journals, housing bores or bearing dimensions before engine reassembly with accurate mics and gauges.

To properly use PLASTIGAGE during reassembly, readings should be taken on the bearing cap half shell while the weight of the crankshaft or piston and rod assembly is supported by the other half shell.

Place a small amount of oil on the crankshaft journal only where the PLASTIGAGE will be placed and wipe any excess oil off with a clean rag. This will result in a more accurate reading by preventing the PLASTIGAGE from sticking to the journal.

Place a strand of PLASTIGAGE across the length of the journal parallel to the crankshaft.

Set the cap in place and tighten bolts to the proper OEM torque specification. NOTE: if the crankshaft is moved at this point it will smear the PLASTIGAGE, resulting in inaccurate readings.

Carefully remove the cap and measure the crushed PLASTIGAGE using the graduations printed on the package. Measure the crush along the entire length of the PLASTIGAGE, noting the highs and lows for proper clearance.

After you have made your measurements, carefully remove the crushed PLASTIGAGE from the components without scratching the bearing or the journal.

PLASTIGAGE is available in four different sizes to check total vertical oil clearance on connecting rod and main bearings. Each package has a measuring scale printed in inches and millimeters. Strips are color coded for easy size identification and are soluble in oil.

MPG1 .001”—.003” (.025 —.075mm) Green
MPR1 .002”—.006” (.050 —.15mm) Red
MPB1 .004”—.009” (.10 —.23mm) Blue
MPY1 .009”—.020” (.23 —.50mm) Yellow

Edited by Whiplash, 07 April 2008 - 12:46 PM.

Conquest owner since 1995. Quest has been on stands for a few years. Engine being built. Powder coating everything. ARP head studs and rod bolts. Caravan head with NEW cam, SS swirl polished exhaust valves, roller rockers, Mild port and polish. More coming,...
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