From the Mitsu Service Guide - 4G15 Mivec
Piston ring side clearance in ring groove mm [LIMIT]
No. 1 0.03 − 0.07 [0.1]
No. 2 0.02 − 0.06 [0.1]
Measured all the pistons, used the small box to get them all at the same height
Use two wrist pins to square the piston ring in the bore
Piston ring end gap mm
No. 1 0.15 − 0.30 [0.8]
No. 2 0.30 − 0.45 [0.8]
Oil ring 0.20 − 0.50 [1.0]
Connecting rod big end thrust clearance mm
0.10 − 0.25 [0.4]
Oil clearance at crankshaft pins mm
0.025 − 0.040 [0.1]
CRANKSHAFT AND CYLINDER BLOCK
Crankshaft end play mm
0.05 − 0.18 [0.25]
Oil clearance at crankshaft journals mm
0.02 − 0.04 [0.1]
Cylinder block gasket surface warp mm
0.05 [0.1]
Cylinder block gasket surface grinding limit (including cylinder head grinding amount) mm
− [0.2]
Cylinder bore diameter mm
75.50 − 75.53 [−]
Taper of cylinder mm
0.01 or less [−]
Cylinder-to-piston clearance mm
0.02 − 0.04
My Measurements of the Block
Bores Measurements| Averages | 0.495 | 76.505 | 0.499 | 76.501 | 0.500 | 76.500 | 0.495 | 76.505 | |
| X is parallel to the crank | 1 is 15mm from top deck | ||||||||
| Y is 90degree rotation of the crank | 2 is 2/3 down the bore | ||||||||
| Pistons Diameter @ Skirt | 76.42 | 76.42 | 76.42 | 76.42 | |||||
| Piston to Wall Clearance | 0.080 | 0.075 | 0.075 | 0.080 | |||||
| Wiseco Recommended Clearance is | 0.08889mm | Bore size | 3.012 | inches | 76.5048 | mm | |||
| OEM Piston to wall is | .02-.04 | mm | |||||||
| Std OEM Piston Bore | 75.5-75.53 | mm | |||||||
| Deck | .05mm | std | 0.1mm | limit | |||||
| Top Ring Bore x | 0.00500 | inches | *Application - Street Moderate Turbo/Nitrous | ||||||
| Second Ring Bore x | 0.00550 | inchens | *Circle Track/Drag Race recommends .0055 & .0060 | ||||||
| Therefore ring gap = [bore size (mm) / 25.4] * (ring bore) | |||||||||
| Top Ring Gap | 0.0150596 | inches | 0.382514 | mm | 0.015 | inches rounded | |||
| Second Ring Gap | 0.0165656 | inches | 0.420765 | mm | 0.016 | inches rounded | |||
We are running 3.5thou piston to wall clearance. Another friend went 4.5thou which isn't really needed due to the Wiseco composition.
From the Mitsu Service Guide - 4G63
Install the piston ring into the cylinder bore. Force it down with a piston, its crown being in contact with the ring, to correctly position it at right angles to the cylinder wall. Then, measure the end gap with a feeler gauge. If the ring gap is excessive, replace the piston ring.
Standard value:
No. 1 0.25-0.40 mm (.0098-.0157 in.)
No.2 0.20-0.35 mm (.0079-.0138 in.)
Oil 0.20-0.70 mm (.0079-.0276 in.)
Limit:
No. 1, No.2 0.8 mm (.031 in.)
Oil 1.0 mm (.039 in.)
