John Vermeech

J. Vermeersch

This letter was obtained from an original owner who wrote FORD back in 1971 and asked them to provide him with any engine specifications / information on the BOSS 351.

FORD’s John Vermeersch, who was Product Specialist at the time responded with this letter and document dated July 22, 1971, highlighting specifications of the BOSS 351 engine.

Please click on each one to enlarge.

Letter 1 Letter 2 Letter 3

Rewrite of page 3 above

Critical bolt Torques (ft-lbs)
Bolt-Cyl, Head Step1	55
Step 2	65
Step3	95-100
Bolt_Intake Manifold	23-25 (5/16)
	28-32(3/8)
Bolt-Connecting Rod	40-45
Bolt-Main Bearing Caps	60-70 (Inner)
	35-40(Outer)
Stud-Rocker Arm	65-75

Critical dimension (inches) BOSS 351
Piston to Bore Clearance		0.0055”-0.0065”
Piston Pin clearance		0.0007” – 0.0009”
Rod End Play Side Clearance		0.025”
Rod Bearing Clearance		0.0025” – 0.0030”
Crankshaft End Play clearance		0.004” – 0.008”
Deck Height Clearance (Nominal)		0.0020”
NOTE: Minimum of 0.0015” can be obtained from milling block
Valve Seat Face Angle:	Intake: 45º		Exhaust 45º
Valve Seat Width	Intake: 0.035” Outer edge of valve (strip)		0.070” Outer edge of valve (street)
	Exhaust: 0.050” Outer edge of valve (strip)		0.080” Outer edge of valve (street)
Hand Hone cylinder wall	Approximately 5 minutes per cylinder with 150-180 grit stone
Piston to Valve Clearance	Intake: 0.100 Manual Transmission		Exhaust: 0.100 Manual Transmission

NOTE: Blueprinting specifications are a guide in preparing an engine for competition. These specs don’t necessarily agree with service or original production specs.

Critical dimension (inches) BOSS 351