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Home >> Cadillac >> 2020 >> CT6 V >> Repair and Diagnosis >> Engine Mechanical >> Engine Mechanical - 4.2L (LTA) >> Specifications >> Engine Mechanical Specifications

Engine Mechanical Specifications

Application Specification
Metric English
General
  • Engine Type
 V-8
  • Displacement
 4.2 Liter 256 cu in
  • RPO
 LTA
  • VIN
 J
  • Bore
 86 mm 3.386 in
  • Stroke
 90.2 mm 3.551 in
  • Compression Ratio
 9.8:1
  • Firing Order
 1-5-4-3-6-8-7-2
  • Spark Plug Gap
 0.75 mm 0.005 in
Block
  • Crankshaft Main Bearing Bore Diameter
 76.993 - 77.007 mm 3.0312 - 3.0318 in
  • Cylinder Bore Diameter
 85.992 - 86.008 mm 3.3855 - 3.386 in
  • Cylinder Bore Out-of-Round - Production Max.
 0.025 mm 0.001 in
  • Deck Flatness
  • Between Holes
 0.1 mm 0.0039 in
  • Any 25 mm Span
 0.025 mm 0.001 in
  • Any 150 mm Span Along Length
 0.05 mm 0.002 in
Camshaft
  • Camshaft Thrust Width
 48.94 - 49.04 mm 1.9268 - 19.307 in
  • Camshaft Bearing Inside Diameter - Front Number 1
 31.000 - 31.020 mm 1.2205 - 1.2213 in
  • Camshaft Bearing Inside Diameter - Positions 2 - 5
 27.000 - 27.020 mm 1.0630 - 1.0638 in
  • Camshaft End Play
 0.055 - 0.470 mm 0.0022 - 0.0185 in
  • Camshaft Journal Diameter - Front Number 1
 30.936 - 30.960 mm 0.9424 - 0.9433 in
  • Camshaft Journal Diameter - Positions 2 - 5
 26.936 - 26.960 1.0605 - 1.0614
  • Camshaft Journal Out-of-Round
 0.008 mm 0.0003 in
  • Camshaft Journal to Bore Clearance
 0.040 - 0.084 mm 0.0016 - 0.0033 in
  • Camshaft Lobe Lift - Exhaust AFM
 6.1695 mm 0.2429 in
  • Camshaft Lobe Lift - Exhaust Non AFM
 6.1488 mm 0.2425 in
  • Camshaft Lobe Lift - Intake AFM
 6.4227 mm 0.2529 in
  • Camshaft Lobe Lift - Intake Non AFM
 6.3913 mm 0.2516 in
  • Camshaft Runout - All Journals
 0.050 mm 0.0020 in
  • Fuel Pump Lift
 5.0 mm 0.1969 in
  • Valve Lift - Exhaust AFM
 10.472 mm 0.4123 in
  • Valve Lift - Exhaust Non AFM
 10.472 mm 0.4123 in
  • Valve Lift - Intake AFM
 10.872 mm 0.4280 in
  • Valve Lift - Intake Non AFM
 10.872 mm 0.4280 in
Connecting Rod
  • Connecting Rod Bearing Clearance
 0.015 - 0.069 mm 0.0006 - 0.0027 in
  • Connecting Rod Bore Diameter - Bearing End
 53.967 - 53.981 mm 3.120 - 3.144 in
  • Connecting Rod Bore Diameter - Pin End
 21.962 - 21.972 mm 0.8646 - 0.8650 in
  • Connecting Rod Length - Center to Center
 138.833 - 138.843 mm 5.4659 - 5.4633 in
  • Connecting Rod Side Clearance
 1.920 - 2.280 mm 0.0759 - 0.898 in
  • Connecting Rod Width - Bearing End
 20.45 - 20.55 mm 0.8051 - 0.8091 in
  • Connecting Rod Width - Pin End
 20.45 - 20.55 mm 0.8051 - 0.8091 in
Crankshaft
  • Connecting Rod Journal Diameter
 50.792 - 50.808 mm 1.997 - 2.003 in
  • Connecting Rod Journal Out-of-Round
 0.005 mm 0.0002 in
  • Connecting Rod Journal Taper
 0.008 mm 0.0003 in
  • Connecting Rod Journal Width
 43.020 - 43.180 mm 1.6937 - 1.7000 in
  • Crankshaft End Play
 0.084 - 0.316 mm 0.003 - 0.0124 in
  • Crankshaft Main Bearing Clearance
 0.036 - 0.056 mm 0.0014 - 0.0022 in
  • Crankshaft Main Journal Diameter
 71.992 - 72.008 mm 2.8343 - 2.8350 in
  • Crankshaft Main Journal Out-of-Round
 0.005 mm 0.0002 in
  • Crankshaft Main Journal Taper
 0.008 mm 0.0003 in
Crankshaft Main Journal Thrust Wall
  • Runout
 0.000 - 0.040 mm 0.0000 - 0.0015 in
  • Square
 0.000 - 0.010 mm 0.0000 - 0.0004 in
Crankshaft Main Journal Width, #2, 4
  • Production
 27.400 mm 1.0787 in
  • Service
 27.300 - 27.500 mm 1.0748 - 1.0827 in
Crankshaft Main Journal Width, #3
  • Production
 27.360 mm 1.0866 in
  • Service
 27.334 - 27.386 mm 1.0761 - 1.0782 in
  • Crankshaft Pilot Bearing Bore Diameter
 29.988 - 30.0125 mm 1.1806 - 1.1816 in
  • Crankshaft Rear Flange Runout
 0.025 mm 0.0010 in
  • Crankshaft Runout
 0.050 mm 0.0020 in
  • Crankshaft Thrust Bearing Clearance
 0.036 - 0.056 mm 0.0014 - 0.0022 in
  • Crankshaft Thrust Surface Runout
 0.040 mm 0.0016 in
Cylinder Head
  • Valve Guide Bore - Exhaust
 6.000 - 6.020 mm 0.2362 - 0.2370 in
  • Valve Guide Bore - Intake
 6.000 - 6.020 mm 0.2362 - 0.2370 in
  • Valve Guide Installed Height
 16.050 - 16.550 mm 0.6319 - 0.5516 in
  • Valve Seat Width - Exhaust Seating Surface
 1.550 - 1.950 mm 0.0610 - 0.0768 in
  • Valve Seat Width - Exhaust Relief Surface
 0.780 - 0.980 mm 0.0307 - 0.0386 in
  • Valve Seat Width - Intake Seating Surface
 1.000 - 1.400 mm 0.0394 - 0.0551 in
  • Valve Seat Width - Intake Relief Surface
 0.500 - 0.700 mm 0.0197 - 0.0276 in
  • Valve Lifter Bore Diameter
 12.008 - 12.030 mm 0.4728 - 0.4736 in
  • Deck Face Flatness
  • Overall
 0.1 mm 0.0039 in
  • Between Head Bolt Holes
 0.03 mm 0.0012 in
  • Any 25 mm span
 0.025 mm 0.001 in
  • Any 150 mm span
 0.05 mm 0.002 in
Pistons
  • Piston Pin Bore Diameter
 21.957 - 21.962 mm 0.8644 - 0.8646 in
  • Piston Ring Groove Width - First Compression Ring
 1.23 - 1.25 mm 0.0484 - 0.0492 in
  • Piston Ring Groove Width - Second Compression Ring
 1.23 - 1.25 mm 0.0484 - 0.0492 in
  • Piston Ring Groove Width - Oil Control Ring
 2.03 - 2.05 mm 0.0799 - 0.0807 in
  • Oil Control Ring
 0.150 - 0.350 mm 0.0059 - 0.0138 in
Valve System
  • Valves
  • Valve Face Angle
 44 degrees (from combustion face)
  • Valve Face Runout
 0.0500 mm 0.0020 in
  • Valve Face Width - Exhaust
 DO NOT GRIND, REPLACE VALVE DO NOT GRIND, REPLACE VALVE
  • Valve Face Width - Intake
 DO NOT GRIND, REPLACE VALVE DO NOT GRIND, REPLACE VALVE
  • Valve Head Diameter - Exhaust
 28.87-29.13 mm 1.1366-1.1469 in
  • Valve Head Diameter - Intake
 35.87-36.13 mm 1.4122-1.4291 in
  • Exhaust Valve Installed Height
 46.88-47.14 mm 1.8457-1.8559 in
  • Intake Valve Installed Height
 47.69 - 47.95 mm 1.8776-1.8878 in
  • Valve Length - Exhaust
 100.64 mm 3.9622 in
  • Valve Length - Intake
 107.14 mm 4.2181 in
  • Valve Seat Angle - Seating Surface
 45 degrees
  • Valve Seat Angle - Relief Surface
 30 degrees
  • Valve Seat Roundness - Maximum
 0.008 mm 0.0003 in
  • Valve Seat Runout - Maximum
 0.025 mm 0.0010 in
  • Valve Stem Diameter - Exhaust
 5.945 - 5.965 mm 0.2341 - 0.2348 in
  • Valve Stem Diameter - Intake
 5.595 - 5.975 mm 0.2344 - 0.2352 in
  • Valve Stem-to-Guide Clearance - Exhaust
 0.035 - 0.075 mm 0.0014 - 0.0030 in
  • Valve Stem-to-Guide Clearance - Intake
 0.025 - 0.065 mm 0.0009 - 0.0025 in
  • Valve Lifters - Stationary Hydraulic Lash Adjuster (SHLA)
  • Valve Lifter (SHLA) Diameter
 11.989 - 12.000 mm 0.4720 - 0.4724 in
  • Valve Lifter (SHLA)-to-Bore Clearance
 0.008 - 0.041 mm 0.0003 - 0.0016 in
  • Rocker Arms
  • Valve Rocker Arm Ratio
 1.68 to 1
  • Valve Rocker Arm Roller Diameter
 17.750 - 17.800 mm 0.6988 - 0.7008 in
  • Valve Springs
  • Valve Spring Free Length
 55.5 mm 2.1850 in
  • Valve Spring Installed Height - Closed
 37.50 mm 1.4764 in
  • Valve Spring Installed Height - Open
 26.03 mm 1.0248 in
  • Valve Spring Load - Closed
 332 - 368 N 75 - 83 lb
  • Valve Spring Load - Open
 611 - 669 N 137 - 150 lb
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