273's are usually only .020 in the hole with flat top pistons. Unlike most LA small blocks. Plus he is running closed chamber heads. No matter what you guys' computers say, 273's are not as finicky as you think. I've actually built and ran them on the street in all kinds of configurations for decades in A bodies, from stock 2 barrel cam to a 284 duration solid cam, from original heads, to 675 318 heads, to "72" 340 "J" heads, Automatic and 4 speed. All through the original manifolds and mostly though the 1965 2.5 inch OD straight through single exhaust. None were dogs, although that is very subjective. A Stock 273 Commando with new 2 barrel pistons and Chrysler rings, a small Isky E-4 cam recently made 265 hp on the Dyno. Nothing trick or fancy, just good machining and tuning ability. That's almost 1 hp per cubic inch with a .425 inch lift and 216 degrees duration @ .050 solid cam, probably even a chevy lobe, go figure. My next build will be with a custom Racer Brown Cam. Can't wait.
