Any input on the best set up for cast iron manifolds?
If you up-cam, and you do not install headers/free-flowing exhaust, you could be leaving over 30hp on the table, and a lot of torque will be lost, thru-out the entire rpm band.
If you intend to run log manifolds, I wouldn't waste money on a cam. The factory 5.9cam is a good street cam for the lighter weight 71 Scamp.
However, my notes say that the truck 5.9s had their cam's installed severely out of time, on purpose, to limit pressure, to prevent detonation.
If it was mine, I would change that.
BTW;
IIRC,
1) the early Magnums still had provision for mechanical fuel-pumps, and
2) IIRC, Hughes still offers akit to convert them to mechanical pump, but you'll need a timing cover with the pump-mount.
3) If you ditch the serpentine system, you'll have to change waterpumps too, for two reasons;
a) the serpentine pumps run backwards, and
b) just try and make the gasket seal, lol.
There's a few threads that detail this swap.
4) from memory, the 5.9 cam is; chit I forgot, I'll be back
EDIT,
I lost my notebook but then I found it!
My notes say that the 5.9 cam is
250/264/110, and .411/.430 lift.
The factory install is listed at Icl of 119* ..... Which would lead to an Ica of 64*, which, at 9.2 Scr, should make pressure of 140psi@800 ft elevation. and that's why, at low rpm, it feels like a pussy.
That cam needs to be advanced to around split overlap, say in at 106*, for an Ica of 51* which should increase the pressure to ~160psi, thus turning the pussycat into a tiger from just about idle to around 3600rpm..
The now working overlap of 37 degrees , is not far from the 340 cam's 44*, Unfortunately, the lobes on this cam are superslow, so the 050 numbers are pretty tame, 182/194, but, the lifters should last nearly forever.
That's what my notes say, which notes were gleaned from the members of FABO.
Elsewhere; the 5.9M cam is said to be
249/269/109, .410/.417lift,
Which if correct, then the overlap jumps to 41*, and installed on split-overlap, the Ica would be 49*, and the pressure would rise another 2psi.
I have not found the 050 numbers for this cam.
Either way, for this application, I wouldn't throw the factory 5.9 cam away, cuz pressure in the 160s is gunna be hard to find with an aftermarket cam, without increasing the Scr.
And when the pressure goes down, it takes the torque with it.