383 cam standard vs magnum/super commando?

[woodwiz]

What do the experts on the forum know of the 383 in the dodge or plymouth cars that had a different cam put in to bump up HP? I have a 70 RR with the orange block that i heard years ago was called a super commando in the plymouths and a magnum in dodge's. Is their a significant difference between the stock (blue) block 383 and the HP (orange) block 383. Also is it true that the cams for the HP 383's was a 440 cam?......Thanks!

 

[Ranger]

Also is it true that the cams for the HP 383's was a 440 cam?

That's my understanding.

 

[V.R.D]

look in the factory service manual it will tell you the cam shaft speck's

 

[droptop]

Absolutely nothing different about the 383 blocks themselves other than their color. And yes, the Road Runner engine used the 440 cam and the larger valve 906 heads.

 

[woodwiz]

Well that explains the very nice cam like rumble from this 383,even with the factory headers.

 

[Palmer Moe-par 68]

Besides the cam and heads hey also have the larger exhaust manifolds with better flow that are specific to the hp motors. The intake manifold I believe is different from a standard 383 intake, but not sure what the difference is other than part number. Lastly, the pistons might be different in order to give it the slighty higher 10.5 to 1 versus the regular 383 10 to 1, or the head design accounts for that.

 

[Photon440]

Even the regular 2 barrel 383 had the 906 heads in 1968. FSM also shows 9.5 compression in 1970 for four barrel 383 vs. 8.7 for the two barrel. Also, the FSM lists higher valve spring pressure for the road runner 383 vs. the regular 4bbl 383.

 

[CompSyn]

The compression ratio numbers printed in FSM's were influenced by the marketing department and not to be taken at face value. A 383HP with 906 heads had an actual compression ratio of around 9.3:1, on a good day.

This is why cam selection for a 383 is critical as to not over-cam it.