273 or NOT 273?

polyjohn said

The only problem with the 273 is the small bore size.
To make good power you need a 340 bore to make the heads flow properly.
The factory made a good performance engine in the 273 commando, but things have moved on.
Forged crank, fully floating pistons, adjustable valve gear.
Nice closed chamber heads that flow nice with 318 or 360 valves.

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Cast cranks are much lighter and need external balancing which can be a pain.

From memory the 318 cast crank was still neutral balance so all good there.
Then the 340 got cast cranks in 72 and the external balance thing raised its ugly head.
Then the 318 got the heavier truck rod too and it gets complex in the 70's.

Its the big-blocks that suffer with the external balancing nightmares...:mob: