WHAT MAKES A 351C A BOSS 351?

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Most People Don't Know The Difference In A Regular 351C And A Boss 351C. On This Page I Will Attempt To Explain.  No, mine is not an actual BOSS 351 but the power output should be very close if not more.  More or less I liked the name and decided to use it.

Ok, Here Are The Facts According To The Manuals And Various Magazines And Books I Have. Lets Start With The Basics: (Block, Heads, ValveTrain, Crank, Rods, Pistons, And Intake)

BLOCK

The Boss Block Is The Same As All Other 351C's But Almost Always Has The 4 Bolt Main Caps. Jack Roush, A Popular Car Owner In NASCAR And 351C Builder, Said That "Virtually Any 351C Block Can Be Used, Since There Is No Difference In Materials Or Strength." He Also Goes On To Say That The 2 Bolt Main Caps Are Just As Strong As The 4 Bolt Caps.  Boss Blocks Are Said To Be Selected For Hardness.  Hardness Is From Higher Nickel Content.

HEADS AND VALVE TRAIN

The Boss 351C Has The 4V, Quench Combustion Chamber Heads (64.6-67.6 cc's) That Were Only Available In 1970 And 1971. Its Advantages Also Include An Adjustable Valve Train With Hardened 1.73 Rocker Arms, 7/16-inch Screw In Studs, Guide Plates, And Hardened Pushrods To Accommodate The Solid Lifter Cam That Came In The Engine. In Special Order Cases, Needle-Bearing Rockers Were Used As A Fulcrum Kit From Ford. The Valve Guide Bosses Were Machined To Accept Special Spring Seats To Keep The Bottom Of The Valve Spring From Shifting. The Boss 351 Also Came With Heavier Valve Springs, Retainers, And A Single Groove Valve Instead Of The Multiple Groove Valves That All Other Cleveland Heads Had. The Single Groove Valve Was Reccomended For High RPM Use Because The Boss 351, With Its 2.198 Intake And 1.715 Exhaust, Has To Be Wound At 7,000 RPM For Max Power. From The Factory, The Boss Came With Aluminum Valve Covers That Gave It A Distinct Racing Look. Stamped On Them Was A Boss 351 Tag. One Final Note, The Boss 351 Head Is Exactly The Same As A Boss 302 Head.

CRANKSHAFT

All 351 Cleveland Crankshafts Came With Cast Nodular Iron Cranks. The Only Difference That The 351 Boss Crankshaft Has From The Normal 351 Cleveland Is That It Is Selected For Higher Nodularity. In Other Words, It Is Said To Be A Bit Stronger Than Say A 2V Or A 4V Crank.

RODS & PISTONS

The Boss 351 Came With Similar Looking Rods Like The Rest Of The 351 Cleveland's Had With A Few Exceptions. It Was Forged Of 1041 Steel, Shot-peened And Magnafluxed, and Came With 180,000 psi 3/8-inch Bolts And Nuts. The Rod Is Said to Be Able To Withstand Up To 8,000 RPM.

As For Pistons, The Boss 351 Came With Forged Pop-up Pistons (Or Sometimes Called Dome Pistons) That Rendered A 11.1:1 Advertised Compression Ratio.  Other Sources Have Confirmed That The Boss Actually Had An 11.7:1 Compression Ratio When Measured.  These Pistons Are Easy To Distinguish From The Regular 351 Cleveland Pistons.

INTAKE MANIFOLD

Well, The Boss 351 Came With A "High-rise" Dual Plane Intake Similar In Performance To The Cast Iron 4V Intakes But The Aluminum It Was Made From Was 31 lbs. Lighter And Had A Standard Carburetor Flange. Unlike The Boss In 71, Its Sister Engine-The Cobra Jet 351, Had A Spreadbore Flange. On Top Of The Boss Intake Sat An Autolite Model 4300-D 4V Carb. That Flowed Approximately 600-cfm.

IGNITION

The Boss 351 Came With A Dual-Point, Dual-Diaphragm, Centrifugal-Advance Distributor. It Was An Improvement Over The Single Point Version Because It Would Allow For A Much Healthier Cam Profile And You Could Easily Run An Auto Transmission.

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