RPO code for a 350 hp/410 tq 396 big block engine found in Camaros, Chevelles and Novas from 1967 up thru 1970. It was not produced after 1970. The same engine was rated at 360 hp in 1966.
This was the middle of the road 396 during the muscle car years. The only other 2 396 engines were the 325 hp model, RPO code "L35" and the top dog 396 RPO code "L78".
The L34 engine used a hotter hydraulic camshaft than the L35 did. It also used a Quadrajet 4 bbl carbureator, and a set of oval port heads with 2.06/1.72 valves, casting code 3964290. The compression ratio was set at 10.25:1. The blocks were usually 2 bolt blocks (though some claim 4 bolts were avaliabe). It's also rumored some came with forged cranks while others say nodular.
The L78 396 however used a solid lifter camshaft and a pair of rectangular port heads, a 780 Holley carbureator, a 4 bolt main block with forged crank and an 11:1 compression ratio.
I have an L34 396 in my 1970 Chevelle