Poly 318, 390, 402 Camshafts

Before we really dive into bump sticks, let us put the rumors to bed: LA and A-block camshafts and lifters DO NOT interchange. The LA camshaft will physically slide into an A318 block and accept the timing set, but the cam lobes are of different alignment on an A-block for its canted valve configuration, whereas LA cam lobes are aligned for the inline valves of LA wedge heads (see Figure 1 below).While the 1957 – 1958 V800 A318 boasted the hottest factory cam, it was still undersized for what the A318 can make use of with factory spec equipment and certainly for stronger modifications. While mainstream cam manufacturers have given up on the A318 and we have lost other grinders like Chris Nielson (2017), we are lucky to have some custom cam grinders still around, including Schneider, CamCraft, and Racer Brown. Do not throw out old A-block camshafts since blanks are limited and a regrind might be the most viable option. Cam selection is a precise process that depends on multiple vehicle variables from the engine back to the rear tires and should be discussed with the cam manufacturer. The following profiles are ballpark examples and should not be considered the definitive cams for every application. My thanks to Gary Pavlovich, and the tech support at Schneider, CamCraft, and Racer Brown for fielding my questions on the following profiles and my description notes. All specs below are with factory 1.5:1 rocker arms.

Factory Cam Profiles for Historical Comparison Only

V800 2×4-barrel

Intake Duration (gross):256
Exhaust Duration (gross):256
Intake Duration (.050”):208
Exhaust Duration (.050”):208
Intake Valve Lift*:.405″
Exhaust Valve Lift*:.405″
Lobe Separation:110
Valve Lash:.017″ hot
RPM Range:1800-5500

2- and 4-barrel

Intake Duration (gross):240
Exhaust Duration (gross):240
Intake Duration (.050”):198
Exhaust Duration (.050”):198
Intake Valve Lift:.400″
Exhaust Valve Lift:.400″
Lobe Separation:111
RPM Range1500-4400

Popular for Mild Street Build A318
  • 3.23:1 or lower gearing, slightly higher stall converter, and headers beneficial but not necessary. Mild lope with good vacuum.
  • Contact the manufacturers for hydraulic grind availability.

EH-2 (courtesy Racer Brown)

Intake Duration (gross):264
Exhaust Duration (gross):264
Intake Duration (.050”):220
Exhaust Duration (.050”):220
Intake Valve Lift:.450″
Exhaust Valve Lift:.450″
Lobe Separation:110
RPM Range:2000-6000

264H (courtesy Schneider)

Intake Duration (gross):264
Exhaust Duration (gross):264
Intake Duration (.050”):208
Exhaust Duration (.050”):208
Intake Valve Lift:.435″
Exhaust Valve Lift:.435″
Lobe Separation:112
RPM Range:1800-4800
Popular for Performance Street/Strip Build A318, Milder A390/A402
  • 3.54 or lower gearing, headers, and high-stall converter necessary. Decent lope and vacuum.

SSH50 (courtesy Racer Brown)

Intake Duration (gross):274
Exhaust Duration (gross):274
Intake Duration (.050”):222
Exhaust Duration (.050”):222
Intake Valve Lift:.477″
Exhaust Valve Lift:.477″
Lobe Separation:110
Valve Lash:0.015″ hot
RPM Range:2400-6500

274F (courtesy Schneider)

Warning: Checking valve clearance at or above .480” lift is a must with A-block pistons.

Intake Duration (gross):274
Exhaust Duration (gross):274
Intake Duration (.050”):230
Exhaust Duration (.050”):230
Intake Valve Lift:.480″
Exhaust Valve Lift:.480″
Lobe Separation:110
Valve Lash:0.014″ hot
RPM Range:2500-6500
Popular for Performance Street/Strip A390 and A402 Strokers
  • 3.73 or lower gearing, headers, and high-stall converter necessary. Strong lope with lower vacuum.
  • Warning: Checking valve clearance at or above .480” lift is a must with A-block pistons.

SSH25 (courtesy Racer Brown)

Intake Duration (gross):286
Exhaust Duration (gross):286
Intake Duration (.050”):238
Exhaust Duration (.050”):238
Intake Valve Lift:.485″
Exhaust Valve Lift:.485″
Lobe Separation:110
Valve Lash:0.015″ hot
RPM Range:3000-7000

284F (courtesy Schneider Cams)

Intake Duration (gross):284
Exhaust Duration (gross):284
Intake Duration (.050”):240
Exhaust Duration (.050”):240
Intake Valve Lift:.480″
Exhaust Valve Lift:.480″
Lobe Separation:110
Valve Lash:0.015″ hot
RPM Range:3000-7000

Figures
Mopar A-block poly canted valves
Figure 1: A-block Canted Valves Detail