5.4 L Engine Tolerance Specs

Below is a list of tolerances for the Boss 5.4 lt engine, The specifications have a minimum and maximum number , The maximum number is worn out and unserviceable. Experienced engine builders will sometimes very from the recommended sizes to meet their performance goals.

Cylinder Bore;

The factory Ford standard cylinder bore is 90.215 mm / 3.6305 in , piston to bore tolerances will be dependant on the brand of piston being used on your application . We typically have used the Manley forged piston, Manley recommend piston to bore tolerances of  0.0762 mm / .003 in , although we run .0635 mm / .0025 in


The crankshaft fitted to the Australian 5.4 engines was a forged steel item that is very strong. It has a stroke of 105.8 mm / 4.1653543 in , bearing sizes are available in std , .25 mm / .010 in,  0.50 mm / .020 in . The Ford recommendations for the conrod to bearing tolerances was 0.068-0.026 mm / .0025 -.001 in. Note the higher tolerances number are seen as worn out, running high rod to crankshaft tolerances will lead to a shortened bearing life and you will also see lower oil pressure. typically as a guide we aim for rod to crankshaft journal tolerance of .75 of the recommended max so that will be  0.047625 mm/.001875 in.

Crankshaft to main bearing factory Ford tolerances were .048-.024 mm / .001891-.0009 in , once again the maximum tolerance number is seen as worn out, as a guide we use .75 of the maximum tolerance and that would be 0.0360172 mm / 0.001418 in. If wider tolerances are used, the engine will see short engine bearing life and lower oil pressure.

Main bearing journal diameter maximum taper (straightness) .004 mm / .0002 in

Con Rod

Center to center of conrod 161.1 mm /6.6575 in. Conrod width 23.876 mm / .940 in. Conrod to crankshaft sideways clearance per pair of conrods should be 0.0381-0.0635 mm / .0015-.0025 in

260 engine Corod pin diameter 22.0 mm /  0.866142 in

290 , 302 , 315 engines conrod pin diameter 23.00 mm / 0.905512 in

Note; Most aftermarket rods use a 22.00 mm / .0866142 in

Torque settings

The below listing is the factory Ford torque settings , many of the bolts inside of the 5.4 l Boss engine were what is called torque to yield, this means they are single use only, its recommended to replace the factory Ford cylinder head & main cap bolts along with side cap bolts with arp studs and bolts.

Factory Ford Torque settings;

  • Camshaft Sprocket bolts tighten to 40 NM then tighten an additional 90 degrees these bolts are single use.
  • Con rod bolts , Stage one tighten to 25 NM, Stage two tighten to 45 NM, Stage three tighten an additional 90 degrees. Note; the con rod bolts are torque to yield and must be replaced after being used each time
  • Crankshaft balancer bolt , four stage install , stage 1 tighten to 90 nm, stage 2 loosen one full turn, stage 3 tighten to 50 nm, stage 4 tighten an additional 90 degrees.
  • Crankshaft main bearing bolts (Vertical) Crankshaft side cap bolts (cross mounted) tighten main cap bolts (vertical) to 40 NM then tighten an additional 90 degrees. Side cap bolts tighten to 30 nm then an additional 90 degrees , all main cap bolts and side cap bolts are single use and must be replaced after use.
  • Cylinder head bolt, Stage one tighten cylinder head bolts to 40 nm, stage two tighten an additional 90 degrees, stage three tighten an additional 90 degrees. note the cylinder head bolts are torque to yield bolts and must be replaced after being used.
  • Dipstick tube bolt 10 nm
  • Exhaust manifold bolts / nuts 23-27 nm
  • Flywheel bolts 73-87 nm
  • Ignition coil covers 10 nm
  • Oil filter adaptor bolts 25 nm
  • Oil pan drain plug 11-16 nm
  • Oil pressure switch 12-16 nm
  • Oil pump bolts 10 nm
  • Oil pump pick up to oil pump bolts 10 mm
  • Oil pick up tube to main cap spacer 25 nm
  • Power steering pump bolts 25 nm
  • Radio ignition interference capacitor 10 nm
  • Rear main seal retainer bolts 10 nm
  • Spark plugs 10 nm
  • Timing chain guide bolts 10 nm
  • Timing chain Tensioner bolts 25 nm
  • Water pump bolts 20-30 nm
  • Water pump pulley bolts 25 nm
  • Power steering bracket lower bolts 25 nm
  • Motor mount cross bolts 80 nm
  • Motor mount Through bolts 80 nm

ARP Fastener

  • ARP head studs p/n 256-4201 Torque cylinder head in three steps following the std torque sequences from center of head out, step 1 30 ft-lb, step 2 60 ftl-lb and last step 3 to 85 ft-lbs ARP head stud instructions available HERE
  • ARP main studs p/n 156-5802 torque main studs to 65 ft-lb, ARP main stud kit instructions HERE 
  • ARP side block to main cap 9 mm bolts. torque to 30 ft-lb using ARP ultra-Torque Fastener Assembly Lubricant. seal under head of bolt with silicon
  • ARP cam to camshaft 10 mm bolts. 65 ft lbs using ARP ultra- Torque Fastener Assembly Lubricant .

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