* Plymouth ------------1964 Belvedere {Sedan} ------ 1968 Road Runner {Pillared Coupe}
* Engine ----------------- '426' Commando --------------- Road Runner 383
* Shipping Weight -------- #3347 lbs. --------------------- #3422 lbs.
*Weight-to-Horsepower --- 9.17 --------------------------- 10.22
* Bore................................ 4.25"...................................... 3.75"
* Stroke............................. 3.75"...................................... 3.38"
* Compression Ratio......... 10.3 - 1 ................................. 10.0 - 1
* Advertised HP............... 365 HP @ 4800 RPM's ........... 335 HP @ 5000 RPM's
* Advertised Torque........ 470 Ft/Lbs. @ 3200 RPM's .... 425 Ft/Lbs. @ 3400 RPM's
* Engine Dyno HP ........... 315 HP @ 4700 RPM's ........... 310 HP @ 5000 RPM's
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Drag Race Test
Both cars equipped with;
* 4-Speed Transmission
* Hurst Shifter
* 3.91 Gears w/Sure-Grip
* Cheater Slicks {7" Width x 28" Tall}
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1st Gear
Despite being {+75 lbs.} heavier, the Road Runner would get off-the-line first.
The 383 gains the advantage because of the shorter engine stroke, and quicker RPM gain.
The '426 Street Wedge' was notoriously sluggish coming out-of-the-hole.
The Road Runner would jump out to a '3/4' car length lead thru 1st-Gear.
But, by the end of 1st-Gear, the bigger 426 engine {+43 cubic inches} would start to make it's move.
2nd Gear
Advantage for the 426-S 'Street Wedge', as this engine had 'strong' Mid-Range Torque.
Once the RPM's got up in the Engine, the 426-S would start to breath, and catch the 383 {shorter stroke}.
By mid-way thru 2nd-Gear, the 426-S would pull 'even' with the Road Runner 383.
And, by the end of 2nd Gear, the 426-S would have a 'slight lead'.
3rd Gear
The 426-S would add to it's 'advantage' thru early 3rd-Gear, and continue to pull on the Road Runner 383 by
mid-way thru 3rd-Gear.
The 426-S {+43 Cubic Inches} would extend it's lead to a full car-length by the end of 3rd-Gear.
4th Gear
A 'surprise' here. What should be expected, is that the Belvedere 426-S {with +43 Cubic Inches} and longer stroke,
should pull away from the Road Runner 383.
But on 'Top End', the 426-S would starve for fuel, and flatten out.
1} The Carter AFB {575 CFM} limited Air-Fuel mixture.
2} The low-profile Intake Manifold would restrict breathing.
3} Also, the 'weak' Valve Springs would float out at 4800 RPM's.
The Road Runner 383 would make a move, and nearly catch the Belvedere 426-S at the 'Traps'.
1} The Carter AVS {625 CFM} would provide more Air-Fuel mixture.
2} The better design Intake Manifold would provide better flow on Top-End.
3} More Cam {Lift and Duration}, with higher load-rate Valve Springs.
4} Better flowing Cylinder Heads.
5} Better Exhaust System.
