440 six pack question

[moparmuscle1970]

Okay, it is my understanding that the motors' horsepower ratings were lowered for insurance purposes. A 426 Hemi rated at 425 hp actually produced 500 hp, and the 340 six pack was rated at 290, but actually put out 350. Now, a 440 six pack is 100 cubes bigger than the 340(my great mathematical ability at it's finest), so is it reasonable to say that a 440 six pack puts out 450 hp? My 440 is not a true six pack motor, but is a magnum, is there any major difference? ps im trying to replace my double post and dont know how this is gonna work, so  dont get mad if you see this twice as im not sure how it will work!    thnks, mm                                                                                                                                                                

[Andrew]

The reason the 340 sixpack and 426 hemi were underrated so much was mainly because they were chryslers racing engines, the other engines wernt underrated so much as they didnt really need to be. Also, diff between a 440 sixpack and 440 magnum is the sixpack has 3 2bbl carbs on a special intake manifold. The 440 magnum had a single 4bbl carb on a 4bbl intake manifold, so the sixpack had more power than the magnum but about the same amount of torque.

[moparmuscle1970]

Thanks for answering about the racing motors, but what I meant about the difference between the magnum and six pack wasnt a question about carburetion-i have a six pack setup, including a 69 cast iron intake. I just thought that an actual six pack motor had different rods and maybe bigger valves. I'm pretty sure they use they same 906 heads though, right?

[ksierens]

As far as I know the six-pack motor had a higher compression, and a forged crank.

[6packCuda]

I believe they had different rods also.

[moparmuscle1970]

Also, about the 383 magnum. What makes it a magnum vs a regular 383? I was always under the impression that a magnum had 440 heads.

[Chryco Psycho]

Manguns had better cams , Exhaust manifolds , windage trays , valave springs etc , both 383 & 440 used the same heads