Engine Details

The 1967 Chevelle SS
OEM Available Options:

  • RPO L35 = 396 cu.in. w/325 hp at 4,800
  • RPO L34 = 396 cu.in. w/350 hp at 5,200
  • RPO L78 = 396 cu.in. w/375 hp at 5,600
    (Dealer Option Only in ’67)

The 1973 LS4

(Engine from the Donor Car)

  • Horsepower: 270 hp @ 4,400 RPM
  • Torque: 380 lb./ft. @ 2,800 RPM
  • Compression Ratio: 8.25:1
  • Camshaft, GM #353040
  • Heads = 353049…..73-84…oval…OPEN…454, 122cc chamber, 255/119cc ports

“Warmed Over” Basic Strategy

The basic strategy targeted the car’s usage toward “road-rallying” vs. “drag racing”.

  • Emphasis was on “handling curves” vs. “straight-line acceleration”.
  • More Torque vs Max Horsepower – To get power in lower RPS vs a screaming demon.
  • Move the ’73 LS4 engine towards a ’70 LS5 or LS6 configuration.

“Warmed Over” Details

  1. Pistons Went from stock flat-top with reliefs to domed:
    • TRW L2399F30 – 454ci Open Chamber Head Race Pistons, .030” Overbore
      • Piston Dia.: 4.280”;
      • Piston Top: .095cc Dome
      • Pressed or Floating Pin (I used pressed).
      • Ring Grooves: 5/64”, 5/64”, 3/16”
      • Comp Ratio: 9.24:1 w/122cc Heads (was 8.25:1),
  2. Heads = Casting #353049 (pretty sure but not verified)
    • Specs: Used form 73 to 84; Oval (small) Ports 255/119cc; OPEN chamber ≈122cc
    • Valve Sizes increased
      • From (I/E) 2.06/1.72 to 2.19/1.88
  3. Cam
    • Original 396 Options:
      • L34 = Hyd, 0.398/0.398 @ 198°/198° (@.050) CL 113 (114?)°
      • L35 = Hyd, 0.461/0.480 @ 214°/218° (@0.050) CL 115°
      • L78 = Mech, 0.520/0.520 @ 242°/242° (@0.050) CL 114°
    • LS4 was GM Part 353040
      • Lift = 0.440 / 0.440 ( I / E )
      • Duration = 210° / 210° ( I / E @0.050 ) @ 110.5° LSA
    • Installed = Crane Cams Hi-Intensity Hydraulic HIT-280-2-NC
      • Lift = 0.525 / 0.550 ( I / E )
      • Duration = 224° / 234° ( I / E @0.050 ) @ ??° LSA
        Advertised Duration = 280° / 290°
    • NOW – Thinking about a Roller Cam and Roller Rockers.
      • Any Suggestions?

Engine Rebuild Photos