J. Vermeersch

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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 Torque (ft-lbs)  

Bolt-Cyl, Head Step1


Step 2




Bolt_Intake Manifold

23-25 (5/16)



Bolt-Connecting Rod


Bolt-Main Bearing Caps

60-70 (Inner)



Stud-Rocker Arm



Critical Dimension (inches) 


Piston to Bore Clearance



Piston Pin clearance

0.0007” – 0.0009”


Rod End Play Side Clearance



Rod Bearing Clearance

0.0025” – 0.0030”


Crankshaft End Play clearance

0.004” – 0.008”


Deck Height Clearance (Nominal)




Note: Minimum of 0.0015” can be obtained from milling block


Valve Seat Face Angle:

Intake:   45Ί

Exhaust 45Ί

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.



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