The 1991–2001 Chevrolet Gen V and Gen VI big-block V-8 engines have a reconfigured oil system compared to earlier Chevy Mark IV big-blocks. One big change is that an oil cooler is now standard equipment on production Gen V/VI installations. To support this feature, Gen V/VI blocks include oil cooler feed line inlet/outlet provisions near the reconfigured oil pan rail ahead of the oil filter mount. Oil is routed out of the block through the rear outlet nearest the oil filter pad, and returned through the inlet in front. These new taps eliminate the need for the additional seals, gaskets, and adapters required to plumb oil coolers into most production Mark IV blocks. However, for retrofit or other nonstock usage, you may wish to delete the oil cooler. To do this successfully while maintaining proper oil circulation, reconfigure the fittings and/or install block-off plugs as shown in the photo.
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