I took the SBC out of the Monza for some re-rigging and want to identify it before I re-install. The block has the numbers GM3951511. Can anyone identify this block for me? The specs of the factory parts? Thanks

Donz,
That is an early 400 block, most likely a 4 bolt, however they did make some in 2 bolt config. How long has it been run in salt?
Bob

Thanks for the info Bob. The engine was run in fresh water for years. I purchased the boat last year and have run it in salt water on three occassions.

Does anyone know what I'd need to do to get to 450hp from the standard configuration of this block? I do see that it has been upgraded with a Perfomer intake and a Holley carb.

Thanks

To get that kind of hp out of your 400, you would need a set of heads in the 210-220 port size, 9.5 - 1 compression, a camshaft with 224-230 @ .050, Performer RPM intake or equivalent and upgraded exhaust. Good luck with your build.

Barry