Ok, so Joe, I think most of us know what you want to do, And I would be doing the same thing.
In fact I already have. But generally the cam and springs are chosen together, to put the power at the rpm you need it to be. Then the Scr is adjusted to get the most of whatever the Ica comes to on the chosen cam.
But in your case the engines Scr has already been established. So then it is possible to mathematically
whip up an Ica number that will get the most from the Scr. And once you have that, it's just a matter of generating a hypothetical cam with that Ica on it, to fill your needs. And the we go shopping for it, or just call a grinder.
But if you also have some springs you want to re-purpose, then the cam selection process can maybe be modified to try and fit them in.
Notice the Ica got pushed to being the second parameter, I don't see that as a particular problem, especially for a 360.
Lets review what you got;putting all the pertinent info on the same page; I took the liberty of cutting and pasting and rearranging stuff.
-a fresh 5.9 Magnum(+.030) engine topped with a set of EQ CH318-B 1.88/1.62 heads, with an
I'm assuming PROVEN 9.4Scr.and
-My plan for the build is a hot street/cruise/corner burner
370HP/425TQ ish running 2400 stall and 3.55 gears. and
-Car is B Body 3600#. and
-Looking for torque and HP lower in the power range. Shooting for more like 1800-5800.and
-these heads and the cam listed were used on a bone stock, low mileage magnum 360. -Intake was a an M1 and carb I believe the carb was an 850 cfm. Not my build. The TQ and HP was higher up in the RPM range and not what I would consider a decent but not great street engine. I have the dyno numbers somewhere if anyone is curious. and
-These heads were used with a custom Comp Roller 279/291 230/238 .499; Too radical for my build.
-Cam not determined yet. That is why I am here asking. Looking for information on what I can run with the springs listed.
-What range of lift, Duration, valve timing, etc....
Right away I get a clue;"The TQ and HP was higher up in the RPM range and not what I would consider a decent but not great street engine"
This tells me, well probably everybody, that that 279* cam had a very late Ica, which was killing your bottom end torque. and the 2400 was strangling it, and the 3.55s were forcing the engine to stay in it's chitmode for way too long.So that cam: I'll guess was on a 114 LSA, and if you install that at 110.5 this is what you get;
279/291/114+3.5/57 overlap(56 effective/110 comp/97 extraction/ Ica of70*
installed, it looks like;
Static compression ratio of 9.4:1.
Ica of 70*, and 100ft elevation
Effective stroke is 2.64 inches.
Your dynamic compression ratio is 7.19:1 .
Your dynamic cranking pressure is 141.59 PSI. ......................... 142
V/P (Volume to Pressure Index) is 114 ..................................... 114
And there are your problems; first the low cylinder pressure and second is the 114VP which is waay less than a stock 5.2Magnum of about 124VP or more, perhaps up to 130 so that perfectly explains your opinion of that cam as;"not what I would consider a decent but not great street engine". I don't for a second blame you for ditching that cam. But I did guess at the LSA, for worst case.
So now we know that an Ica of 70*, in this engine,at your Scr of 9.4,is " not a great street engine" ; and you are on the money.... IMO,lol. However, you need close to that cam's .050 specs if you want to get close to your target of 370/425. And that 279 cam already had pretty fast ramps, as far as rollers go. so what do we do?
Well lets back up the bus a bit; you are also handicapping the selection process with the 2400 and 3.55s and 3600# weight. I'm gonna suggest to lower your power expectations so as to not get into another lo-perf bottom end situation, cuz lo cylinder pressure and these handicaps do not play well together. Are you with me?
Ok a minute with the Wallace calculator, and it spit this out;
Static compression ratio of 9.4:1.
Ica of 58*/ 100 ft elevation
Effective stroke is 2.93 inches.
Your dynamic compression ratio is 7.87:1 .
Your dynamic cranking pressure is 159.55 PSI. ............... 160
V/P (Volume to Pressure Index) is 143 ........................... 143
I guarantee you these numbers will make you smile.
160psi lets you burn 89 gas at WOT with a tight Quench , 91 without, but of course 87 at cruising.
A VP of 143 is just over the threshold of where the fun starts (140 IMO). So this will light up the tires with that 2400 and 3.55s. This is where I'd like to be.
But it won't make 370/425
If you just gotta get closer to those number, then lets rerun the numbers with the next bigger cam.And I get
Static compression ratio of 9.4:1.
Ica of 62, still 100 ft elevation
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 7.66:1 .
Your dynamic cranking pressure is 153.97 PSI. ..................... 154
V/P (Volume to Pressure Index) is 134 ................................. 134
So here we have a burns any gas engine anytime, but the VP is down to 88% of the previous 143VP. This combo will not like the 2400TC. To get the off-the-line performance back, you're looking at, at least a 2800, 3000 would be better; and a 3200 would let you keep the 3.55s.
And this is just one cam size. And it still won't make your numbers.
Ok so, lets see what cam will make the 62* Ica, just for kicks.
My first go-to is the weight and gears. 3600 plus driver? is getting heavy. and 3.55s are keeping the engine in the unproductive range, and the 2400 is killing your take off, so what can I do?
I can see this;
264/270/110+0/47 overlap(44 Effective)/118 comp/115 exhaust, Ica of 62* ..
Ok so; as a roller, the typical ramp might be 58* so this will get you [email protected] which will likely power peak just below 5000, and I'll guess 330 hp(with headers and a free-flowing exhaust), and adequate take-off torque.
Ok but lets ramp it up;
If you could find a hydraulic roller with faster ramps, say 48* from advertized to .050, then this cam would be [email protected], and that's another 15hp or more, so now up to 345 hp.
But if you could find a hydraulic roller with 38* ramps, then you get a [email protected] and now yur talking maybe 360 hp. I'm still guessing, but you can see how this all plays out.
All of these have the same Ica of 62*, so the cylinder pressure remains the same, so the launch stays the same. But each one fattens up the midrange power and each has successively, more top-end power capability.
I haven't seen the 38* ramps on anything but a Solid roller cam, so don't spend time looking for it; this was just an exercise.
From the exercise I glean this;
I like the 58* Ica cuz it will not have a problem with the 2400 and 3.55s, yur good to go.
But by 62* you can see the pressure is falling, and the VP is down to 134, about the smallest I could imagine running; I wouldn't run it with a 2400, that's for sure. So for this 9.4Scr combo yur looking at a range of 62 to 58(or less for killer Rubber burning take-off)
Now it remains to be seen, if your springs will work with something in this range, and you won't know that until you actually find a suitable cam.
Happy cam hunting.
Of course you can install any cam outside this range, as in one with a bigger than 62* Ica; but you WILL need a higher stall TC, and depending on how much bigger you chose, you might need a bigger rear gear....................
So that leads us back to the 279*cam you pulled out. All it needs is a 3000/3200TC and maybe 3.91s. It's already a fast-ramp roller and already the size you need to make 370/425.... maybe even a tad more.
It could be a street terror
And the bonus is, that you already know the springs are gonna work ....... lol
And if you are able to cheaply pump up the compression a lil, that will just be icing on the cake.
Happy HotRodding
