Why did Pontiac add those cooling holes to the 421 SD but not to millions of regular everyday Pontiac V8s?
If it was truly beneficial why didn’t they? The added tooling and machining cost could have been a factor.
Perhaps potential long term durability issues?
The 421 SD, produced in very limited numbers mostly for racing, had no factory warranty so any failures wouldn’t end up as a liability.
I’m guessing not many Pontiac engine builders today offer that particular modification on their list of different options, maybe I’m wrong. If it was something that really made a difference everyone would be doing it.
Thread closed.
1964 421 HO block, 370 hp code 45B for manual trans, no special added cooling holes.