1966 Chevelle

Camshaft and Valve Train - Group 0.519

All camshafts with the exception of RPO L78 (396 V8/375hp) used hydraulic lifters set at zero lash. Engine RPO L78 used a mechanical lifter and valve lash is set at .024 (intake) and .028 (exhaust).

All camshafts were cast alloy iron. Both L6 engines (194cid and 230cid) used a Bakelite and fabric composition timing gear setup where the V8 engines used a steel chain and sprocket configuration.

Lobe lift:
L6 engines (194 & 230) ~  .1896 (intake and exhaust)
283 & 327 V8 engines ~ .2658 (intake and exhaust)
396/325hp V8 engine ~ .2343 (intake and exhaust)
396/360hp (L34) engine ~ .2714 intake / .2824 exhaust
396/375hp (L78) engine ~  .3057 (intake and exhaust)

Valve lift:
L6 engines (194 & 230) ~ .3318 (intake and exhaust)
283 & 327 V8 engines ~ .3987 (intake and exhaust)
396/325hp V8 engine ~ .3983 (intake and exhaust)
396/360hp (L34) engine ~ .4614 intake / .4800 exhaust
396/375hp (L78) engine ~ .5197 (intake and exhaust)

Rocker arms are individually mounted stamped steel with ratios of 1.75:1 on the L6 engines, 1.50:1 on the 283 & 327 V8 engines and 1.75:1 on the 396 V8 engine. Push rods are hollow steel with hardened ends on all but the 396 V8 which used carburized steel inserts.

True valve timing on Chevrolet camshafts is milder in most cases than the timing specifications on blueprints indicate. Chevrolet includes clearance ramps in their valve timing specifications for hydraulic lifter camshafts. The clearance ramp is the portion of the camshaft that gradually takes up the clearance of the valve train.

1967 saw the first year the 396 V8 camshaft abandoned the grooved rear journal and matching bearing in the engine block in favor of a smooth journal like the 283/327 V8. Any camshaft from a 1965 or 1966 396 engine can be used in a 1967 or later block but not the other way around. This groove is clearly visible in this photo on the camshaft on the left.

Grooved rear journal unique to 1965 and 1966 396 engines
Photo courtesy Bruce Tester

Note the oil groove in rear cam journal of this 396 V8 camshaft on the left. Both 1965 and 1966 396 V8 engines require this groove along with corresponding rear cam bearing. Most aftermarket camshaft manufacturers DO NOT list the 65/66 396 V8 in their catalogs due to this groove. However, any later camshaft will work if grooved and most aftermarket cam suppliers will either groove the cam for a nominal fee or send you the specifications so you can have your local machine shop perform the operation.

VALVE TIMING (Crankshaft degrees)

  Excluding
Ramps		 Including
Ramps
L6-194 & 230 Cu. In.    
  Intake Valve (zero lash)    
    Opens - BTC 16° 62°
    Closes - ABC 48° 94°
    Duration 244° 336°
  Exhaust Valve (zero lash)    
    Opens - BBC 46° 30' 92° 30'
    Closes - ATC 17° 30' 63° 30'
    Duration 244° 336°
V8-283 & 327 Cu. In.    
  Intake Valve (zero lash)    
    Opens - BTC 12° 30' 32° 30'
    Closes - ABC 57° 30' 87° 30'
    Duration 250° 300°
  Exhaust Valve (zero lash)    
    Opens - BBC 54° 30' 74° 30'
    Closes - ATC 15° 30' 45° 30'
    Duration 250° 300°
V8-396 Cu. In.    
  Intake Valve (zero lash)    
    Opens - BTC 28° 40°
    Closes - ABC 78° 102°
    Duration 286° 322°
  Exhaust Valve (zero lash)    
    Opens - BBC 75° 87°
    Closes - ATC 31° 55°
    Duration 286° 322°
V8-396 Cu. In.- RPO L34    
  Intake Valve (zero lash)    
    Opens - BTC 40° 56°
    Closes - ABC 80° 114°
    Duration 300° 350°
  Exhaust Valve (zero lash)    
    Opens - BBC 88° 110°
    Closes - ATC 32° 62°
    Duration 300° 352°
V8-396 Cu. In. - RPO L78    
  Intake Valve (opens with .024 lash)    
    Opens - BTC   54°
    Closes - ABC   102°
    Duration   336°
  Exhaust Valve (closes with .028 lash)
    Opens - BBC   102°
    Closes - ATC   54°
    Duration   336°

(1) Engine RPO L79 (327 V8/350hp) figures are not included as this was a late March, 1966 option and specifications are not available at press time. Additionally, GM reports no sales of the L79 engine in the 1966 Chevelle.