L-78 engine Birth date

[Stefano]

I have never Dynoed the different exhaust manifolds side by side but it would be no where near a 50 hp difference.

The top dog prior to the mystery motor was the 409/425. GM could not go backwards in the public eye/marketing, at least at the initial release of their new solid lifter engine.

Some early '66 L78 Chevelles have been documented as showing the L78 option rated at 425hp.

I believe Bill Thomas' Blue printing guide/book has a dyno chart or info showing that the L78 could produce 425hp if brought to exact specs.

The First 427/L72s were factory rated at 450hp.