· Valued Member
I did some of the original dyno development on the 340 when I was running the dynos at Chrysler. The 4 bbl 340 running under lab gross conditions (no air cleaner, deep sump pan, max spark and F/A, cold intake manifold, no accessories, and lab exhaust) would make in the range of 320 to 330 HP at 6000 rpm. The 275 HP advertised number was for NHRA Stock classificationn to make it more competitive.The 340 was definitely under rated at 275 H.P.
An interesting thing is Chevy built a specific 1969 LM1 combination to compete against it in NHRA.
The 1969 LM1 was a 350 4 bbl under rated at 255 H.P. and is still competitive today.
1969 Nova and Camaro SS models had the 300 H.P. version as standard equipment.
Only lighter non SS cars got the 1969 LM1 package to compete against the light 340 Darts etc.
LM1 cars got Muncie 4 speed trans rather than the Saginaw normally used in cars less than 300 H.P.
Most also received 12 bolt rears instead on the 10 bolt units found in non SS cars.
The 1969 LM1 was discontinued after about Feb 1969 and was replaced by the 350 2 bbl. 250 H.P.