The L19 was available from 1988 to 1995 in 2500 and 3500 trucks, and also in the 1990-1993 SS454 C1500. The general specifications remained very similar for its entire run, other than a block redesign to to new Mark V architecture in 1991.
1988-90 Mark IV
1988-1990 L19’s were Mark IV 454 blocks, with 4 bolt mains and a 2 piece rear-main seal. Air and fuel was supplied 2 barrel throttle body EFI system. The cylinder heads were the ubiquitous peanut port small ovals. Valve-train was non-adjustable with a flat tappet camshaft. Compression ratio checked in at a whopping 7.9:1.
Horsepower was 230 HP at 3600rpm and torque was 385 ft-lbs at a low 1600rpm.
1991-1995 Mark V
In 1991 the new Mark V block was introduced. This was a lighter casting, with a few changes to the cooling and oiling systems. Mechanical fuel pump provisions were removed. The rear main seal was updated to a new 1 piece design.
The intake manifold was updated to a dedicated TBI intake, rather than a 4bbl carbed intake with a TBI adaptor. The 2bbl TB EFI system remained. Compression ratio and cam remained unchanged.
Power ratings remained at 230HP@3600rpm, and 385TQ@1600rpm, barring the 454SS trucks. These gained some power with a higher flowing exhaust system, pumping out 255hp@4000rpm, and 405TQ at 2400rpm.
Detailed Specifications
| Basic Description | |
| Displacement | 7.4L (454ci) |
| Bore | 4.25in |
| Stroke | 4.00in |
| Compression Ratio | 7.9 : 1 |
| Firing Order | 1-8-4-3-6-5-7-2 |
| SAE Net Horsepower @ RPM | 230 @ 3600 / 255 @ 4000 (91-93 454SS) |
| SAE Net Torque @ RPM | 385 @ 1600 / 405 @ 2400 (91-93 454SS) |
| Intake System | |
| Induction | Rochester 2bbl TBI |
| Throttle Bore | 2.0in |
| Flow | 670cfm |
| Camshaft | |
| Intake Duration | 193 @ .050 |
| Intake Lift | 0.398″ |
| Exhaust Duration | 204 @ .050 |
| Exhaust List | 0.430″ |
| Lobe Seperation | 120 degrees |
| Valvetrain | |
| Туре | Nonadjustable, push rod actuated |
| Lifters | Hydraulic Flat Tappet |
| Rocker Arm Ratio | 1.70:1 |
| Cylinder Heads | |
| Туре | Cast Iron Small Oval “Peanut Port” |
| Chamber Volume | 120cc |
| Intake Volume | 208cc |
| Intake Valve Diameter | 2.06in |
| Exhaust Volume | 112cc |
| Exhaust Valve Diameter | 1.72in |
| Head Flow Chart | |
| Lift | CFM (I/E) |
| .100 | 56/44 |
| .200 | 125/87 |
| .300 | 183/111 |
| .400 | 215/130 |
| .500 | 233/144 |
| .600 | 235/150 |
| .700 | 235/155 |
