Torque Specs For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

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The Importance of Following Torque Specifications

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Adhering to the correct torque specifications is crucial when reassembling the Detroit Diesel 71 Series engines. Overtightening or undertightening fasteners can lead to mechanical failure, engine damage, or leakage. Every fastener used in these engines must be tightened to the manufacturer’s recommended values to ensure a safe and efficient assembly.

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Use a Torque Wrench

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Always use a calibrated torque wrench to achieve the specified torque. Avoid using manual estimates or “by feel,” as inaccuracies can lead to misalignment, loose components, or damage to the threads.

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Follow Manufacturer’s Guidelines

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Every component has a specified torque value, based on the bolt size and material. These guidelines are based on extensive testing to ensure optimal engine performance.

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Tighten in Stages

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For critical components like the cylinder head, manifold, and flywheel bolts, tightening should be done in stages using a criss-cross pattern. This method ensures even pressure distribution and reduces the risk of warping or stress on the components.

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Comprehensive Torque Specifications

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Detroit Diesel 2-71 Torque Specifications
Thread Size (in.)	Description	Torque Specifications
		lb-ft	N-m
1/4-20	Standard Torque Specification	7-9	9-12
1/4-28	Standard Torque Specification	8-10	11-14
	Screw-Injector Rack Control Lever	2-3	3-4
5/16-18	Standard Torque Specification	13-17	18-23
5/16-24	Standard Torque Specification	15-19	20-26
	Nut-Lock-Push Rod	15-19	20-26
3/8-16	Standard Torque Specification	30-35	41-47
	Bolt-Air Inlet Housing to Blower	30-35	41-47
	Bolt-Air Box Cover	10-12	14-16
	Bolt-Oil Pan	10-12	14-16
	Bolt-Injector Clamp	20-25	27-34
3/8-24	Standard Torque Specification	35-39	47-53
	Nut-Fuel Jumper Line	12-16	16-22
	Nut-Exhaust Outlet Manifold Flange (Brass)	20-25	27-34
	Nut-Injector Clamp	20-25	27-34
7/16-14	Standard Torque Specification	46-50	62-68
	Bolt-Blower to Block	55-60	75-81
7/16-20	Standard Torque Specification	57-61	77-83
	Bolt-Oil Strainer Shell to Adaptor	30-35	41-47
	Bolt-Connecting Rod to Pin	55-60	75-81
	Nut-Connecting Rod	60-75	81-102
	Nut-Connecting Rod	60-75	81-95
1/2-13	Standard Torque Specification	71-75	96-102
	Bolt-Rocker Shaft Bracket to Cyl Head	90-100	122-136
1/2-20	Standard Torque Specification	83-93	113-126
9/16-12	Standard Torque Specification	90-100	122-136
9/16-18	Standard Torque Specification	107-117	145-159
	Bolt-Flywheel	180-190	244-258
5/8-11	Standard Torque Specification	137-147	186-199
	Bolt-Main Bearing (Boring)	165-175	224-237
	Bolt-Main Bearing (Assembly)	180-190	244-258
	Bolt-Cylinder Head	190-200	258-271
5/8-18	Standard Torque Specification	168-178	228-241
	Nut-Special Self Locking Nut (10SI Alternator)	40-60	54-81
	Bolt-Lube Oil Filter Center	50-60	68-81
	Nut-Alternator Pulley	70-80	95-108
3/4-18	Nut-Standard, Dipstick Tube	30-35	41-47
3/4-16	Standard Torque Specification	290-300	393-407
7/8-14	Standard Torque Specification	475-485	644-658
1-14	Bolt-Crankshaft End (1)	290-310	393-420
1-14	Bolt-Crankshaft End-1-1/2 Hex Head (2)	440-460	597-624
1-20	Nut-Cam and Balance Shaft	250-275	339-373
	Detroit Diesel 2-71 Pipe Plug Torque Specifications
Plug Size (in.)	Description	Torque Specifications
		lb-ft	N-m
1/8-27	Plug-Pipe (3/4 Taper)	10-12	14-16
1/4-18	Plug-Pipe (3/4 Taper)	14-16	19-22
1/4-18	Plug-Pipe (7/8 Taper)	14-16	19-22
3/8-18	Plug-Pipe (3/4 Taper)	18-22	24-30
3/8-18	Plug-Pipe (7/8 Taper)	18-22	24-30
1/2-14	Plug-Pipe (3/4 Taper)	23-27	31-37
1/2-14	Plug-Pipe (7/8 Taper)	23-27	31-37
3/4-14	Plug-Pipe (3/4 Taper)	33-37	45-50
3/4-14	Plug-Pipe (7/8 Taper)	33-37	45-50
1-11 1/2	Plug-Pipe (3/4 Taper)	75-85	102-115
1-11 1/2	Plug-Pipe (7/8 Taper)	75-85	102-115
1 1/4-11 1/2	Plug-Pipe (3/4 Taper)	95-105	129-142
1 1/2-11 1/2	Plug-Pipe (3/4 Taper)	110-130	149-176
1 1/2-11 1/2	Plug-Pipe (7/8 Taper)	110-130	149-176
1/2-20	Plug-Fuel Pump Relief Valve	18-22	24-30
	Detroit Diesel 2-71 Stud Torque Specifications
Thread Size (in.)	Description	Torque Specifications
		lb-ft	N-m
7/16-20	Stud Standard	30-35	41-47

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	Torque Specifications For Detroit Diesel Series 71 (Inline Except 2 Cylinder)
Thread Size (in.)	Description	Torque Specifications
		lb-ft	N-m
1/4-20	Standard Torque Specification	7-9	9-12
	Bolt-Injector Control Shaft Bracket	10-12	14-16
	Bolt-Cam Follower Guide	12-16	16-22
1/4-28	Standard Torque Specification	96-120	130-163
	Screw-Inj. Rack Control Lever	24-36	33-49
5/16-18	Standard Torque Specification	156-204	212-277
	Bolt-Oil Pan (Cast) – Hard Gasket	13-21	18-28
	Bolt-Oil Pan (Low Pan or In Aluminum F/W Hsg. & Front Cover)	10-12	14-16
5/16-24	Standard Torque Specification	15-19	20-26
	Nut-Lock-Push Rod	15-19	20-26
	Bolt-Blower Drive Coupling Rotor Gear	20-25	27-34
	Bolt-Blower Rotor Gear Hub	25-30	34-41
	Nut-Lock Valve Bridge Adj. Screw	20-25	27-34
7/16-14	Standard Torque Specification	46-50	62-68
	Bolt-Tach. Drive	30-35	41-47
	Bolt-Lifter Bracket	55-60	75-81
	Bolt-Valve Bridge Guide (Nylon-Insert)	46-50	62-68
	Bolt-Flywheel Housing Large Hole Cover	30-35	41-47
	Bolt-Blower to Block	55-60	75-81
7/16-20	Standard Torque Specification	57-61	77-83
	Connector-Fuel (Steel Washer)	40-45	54-61
	Nut-Exhaust Manifold	30-35	41-47
	Nut-Connecting Rod	60-70	81-95
	Connector- Fuel (Nylon Insert)	30-35	41-47
	Nut-Connecting Rod	60-70	81-95
	Bolt-Connecting Rod to Pin	55-60	75-81
3/8-16	Standard Torque Specification	30-35	41-47
	Bolt-Camshaft & Seal End Bearing	35-40	47-54
	Bolt-Flywheel Hsg to Idler Gear & Dummy	40-45	54-61
	Bolt-Air Box Cover	10-15	14-20
	Bolt-Rocker Cover Hold-Down Special 12-Point	15-20	20-27
	Bolt-Injector Clamp	20-25	27-34
	Bolt-Oil Pan	10-20	14-27
3/8-24	Standard Torque Specification	35-39	47-53
	Bolt-Accessory Drive to Balance Gear (Steel Disc)	45-50	61-68
	Bolt-Lower Front Cover	25-30	34-41
	Nut-Water Manifold	20-25	27-34
	Bolt-Balance Weight to Hub	25-30	34-41
	Bolt-Balance Weight to Timing Gear	25-30	34-41
	Bolt & Nut-Blower Drive Gear	25-30	34-41
	Nut-Exhaust Outlet Manifold Flange	20-25	27-34
	Nut-Fuel Jumper Line O Ring	13-17	18-23
	Nut-Fuel Jumper Line Flared	11-13	15-18
	Nut-Injector Clamp	20-25	27-34
1/2-13	Standard Torque Specification	71-75	96-102
	Bolt-Flywheel Housing	90-100	122-136
	Bolt-Idler Gear Hub and Dummy Hub	80-90	108-122
	Bolt-Tach. Drive Cover	30-35	41-47
	Bolt-Engine Mtg Brkt to Frt Cover	90-100	122-136
	Bolt-Front Cover (Crankshaft)	80-90	108-122
	Bolt-Flywheel Housing Large Hole Cover	30-35	41-47
	Bolt-Rocker Shaft Bracket to Cyl Head	90-100	122-136
1/2-20	Standard Torque Specification	83-93	113-126
	Bolt-Blower Rotor Gear Retainer	55-65	75-88
	Nut-Oil Pump Drive Idler Gear Shaft	60-70	81-95
9/16-12	Standard Torque Specification	90-100	122-136
9/16-18	Standard Torque Specification	107-117	145-159
	Nut-Crankshaft Bearing Cap	140-150	190-203
	Bolt-Flywheel	180-190	244-258
	Bolt-Flywheel (V-53)	12-16	16-22
	Bolt-Cylinder Head	140-150	190-203
5/8-11	Standard Torque Specification	137-147	186-199
	Bolt-Starter to Aluminum Flywheel Housing	95-105	129-142
	Bolt-Main Bearing (Boring)	165-175	224-237
	Bolt-Main Bearing (Assembly)	180-190	244-258
	Bolt-Cylinder Head	190-200	258-271
5/8-18	Standard Torque Specification	168-178	228-241
	Bolt-Lube Oil Filter Center	50-60	68-81
	Nut-Alternator Pulley	70-80	95-108
	Nut-Special Self Locking Nut (10SI Alternator)	40-60	54-81
	Bolt-Main Bearing (Boring)	140-155	190-210
	Bolt-Main Bearing (Assembly)	155-185	210-251
	Nut-Cylinder Head	190-200	258-271
3/4-10	Bolt-Crankshaft Main Bearing	280-290	380-393
3/4-16	Standard Torque Specification	290-300	393-407
	Nut-Accessory Drive Pulley	120-140	163-190
3/4-18	Nut Standard, Dipstick Tube	30-35	41-47
3/4-24	Bolt-Balance Weight Cover	25-30	34-41
7/8-14	Standard Torque Specification	475-485	644-658
7/8-18	Bolt-Oil Pump Relief Valve Cover	25-35	34-47
1-14	Bolt Crankshaft End	440-460	597-624
1 1/8-18	Nut-Cam and Balance Shaft	300-325	407-441
1 3/4-16	Nut-Transfer Drive Gear (Marsden)	375-400	508-542
	Torque Specs For Detroit Diesel Series 71 (Inline Except 2 Cylinder) Pipe Plug
Plug Size in.	Description	Torque Specifications
		lb-ft	N-m
1/8-27	Plug-Pipe (3/4 Taper)	10-12	14-16
1/4-18	Plug-Pipe (3/4 Taper)	14-16	19-22
1/4-18	Plug-Pipe (3/4 Taper)	38-42	52-57
1/4-18	Plug-Pipe (7/8 Taper)	14-16	19-22
3/8-18	Plug-Pipe (3/4 Taper)	18-22	24-30
3/8-18	Plug-Pipe (7/8 Taper)	18-22	24-30
1/2-14	Plug-Pipe (3/4 Taper)	23-27	31-37
1/2-14	Plug-Pipe (7/8 Taper)	23-27	31-37
3/4-14	Plug-Pipe (3/4 Taper)	33-37	45-50
3/4-14	Plug-Pipe (7/8 Taper)	33-37	45-50
1-11 1/2	Plug-Pipe (3/4 Taper)	75-85	102-115
1-11 1/2	Plug-Pipe (7/8 Taper)	75-85	102-115
1 1/4-11 1/2	Plug-Pipe (3/4 Taper)	95-105	129-142
1 1/4-11 1/2	Plug-Pipe (7/8 Taper)	95-105	129-142
1 1/2-11 1/2	Plug-Pipe (3/4 Taper)	110-130	149-176
1 1/2-11 1/2	Plug-Pipe (7/8 Taper)	110-130	149-176
1/2-20	Plug-Fuel Pump Relief Valve	18-22	24-30
1 1/4-16	Plug-Oil Filter Bypass valve	95-105	129-142
	Torque Specs For Detroit Diesel Series 71 (Inline Except 2 Cylinder) Stud
Thread Size (in.)	Description	Torque Specifications
		lb-ft	N-m
7/16-20	Stud Standard	30-35	41-47

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Parts Catalog for Detroit Diesel 371 Marine and Industrial Engines

Parts Catalog for Detroit Diesel 471 Marine and Industrial Engines

Parts Catalog for Detroit Diesel 671 Marine and Industrial Engines

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Overtightening and Undertightening

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• Overtightening can cause bolts or studs to stretch beyond their yield point, weakening the material and potentially leading to fracture or engine failure.
  

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• Undertightening can allow components to shift under stress, leading to vibrations, leaks, or even catastrophic failure.
  

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Final Checks

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Once assembly is complete, it’s crucial to conduct a final check. This includes rechecking all torque values and monitoring for any signs of leaks or misalignment. Torque should be applied in stages to avoid uneven pressure or damage to components.

By following these guidelines and using the specified torque values, you can ensure that the Detroit Diesel 71 Series engines are assembled safely and efficiently.