383 cam standard vs magnum/super commando?

woodwiz

Well-Known Member
Joined
Dec 10, 2020
Messages
288
Reaction score
204
Location
Tucson,Az.
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!
 

droptop

Well-Known Member
Joined
Sep 11, 2008
Messages
3,854
Reaction score
481
Location
Southern Indiana
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.
 

Palmer Moe-par 68

Well-Known Member
Joined
Feb 26, 2017
Messages
81
Reaction score
22
Location
Seattle, WA
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

Well-Known Member
Joined
Dec 7, 2013
Messages
140
Reaction score
5
Location
Surrey, BC Canada
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.
 
Last edited:

CompSyn

Well-Known Member
Joined
Jun 18, 2010
Messages
237
Reaction score
34
Location
Lewiston, Idaho USA
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.
 
Top