Our L83 cylinder heads were developed specifically for the stock displacement, 5.3L Direct Injected engines to deliver improved cylinder fill in the lower RPM ranges while adding substantial airflow increase in the upper ranges as well. Our testing has shown over 30 hp increase while improving torque below the curve.
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OEM Casting ported and chambered – with valves less springs.
Intake Port Volume:Â Â
Exhaust Port Volume:Â Â
Lift |  Intake Flow @ 28″ |  Exhaust Flow @ 28″ w/ No Pipe |
.300 | 235 | 163 |
.400 | 273 | 201 |
.500 | 290 | 211 |
.600 | 306 | 211 |
.700 | 315 | 211 |
.800 | 322 | 211 |
.900 | 327 | 211 |
Cores must be received within 30 days of receipt of your GPI Ported GEN V L83 Cylinder Heads, must be in acceptable condition, and include usable valves. Please allow up to five business day upon receipt of your return cores for inspection and verification, followed by up to five business days before your refund is processed.
Easier than gutting the old heads
Beautiful porting job by the GPI team. My only objection is the long lead time, which wasn’t really an issue as I was waiting for other items to support the cylinder head swap.
Good
Super fast order, these guys processed my order had the heads worked and shipped with in 3 days