The Dodge Challenger Message Board

Has anyone ever dynoed a Mopar 340 to find out the actual horsepower of the engine. I know 70 and 71s were rated at 275 horsepower, but I understand that the Chrysler engineers said that the 340 was closer to 325 actual horsepower and they were rated lower for insurance reasons. The same goes for Hemi, 425 Horsepower?, more like 500.

Good question. With the little bit of work on my motor, I would guess it to be around 400hp right now. Anyone know what does it costs to get a session on the dyno these days?

As for the 426, I saw an episode of American Muscle car where they did a shoot out with engines from the era. The dyno said 800+ hp (stock). Heard rumors that motor was a ringer thought. Probably started by some Chevy guys.

One of the guys that did the actual Dyno work on the street hemis said they generally made a true 425 HP on the dyno.

I doubt the 340 ever put out more than 280hp from the factory.

Cars given to magazines to test were always tuned for more power by Chrysler engineers.

dave is right the horse power numbers were only conservatively rated maybe off by 5 or 10 horses, as far as the hemi, remember that was a race engine that was de-tuned for the street, so it really hurt the motor, as far as drivability,i hear tell that a fully dressed race hemi put out 750 to 800 horses

I bet the 340 made a little more than the rated 275 H.P. First in 1968 it used a 600 CFM Carter AFB/AVS , then in 1971 they went to the huge 900 CFM Thermoquad, which is why many SuperStockers race with that 71-72 340 'package' not counting the sixpack, but 275-290 is what I feel they actually made. The 426 Hemi heads flow enough for 600 H.P. in stock form with well over 300 CFM port flow through the heads. The valve springs and small factory camshaft would prevent the 800 H.P. mark. Slip in a Crane R-296 Roller and battleship valvesprings and watch that number skyrocket. 800 is a lot of power and to think they used a factory stock motor is simply patronizing our intelligence. What did the factory cars show at the track? Timeslips from that period show it couldnt have made that much power even with slicks.

Timeslips from that period show it couldnt have made that much power even with slicks,that tells it all!

Has anyone here built a hot 340ci with W heads, high comp and all the good stuff, and if so how much HP did you get?