Cams for 318's

At the risk of repeating old information; I gotta say this;
If you marry your whatever cam to a decent DCR, you will never go away unhappy.
Wyrmrider preaches duration from .200 to .200 and whenever you can, you need to keep that in mind. If you start from the .200 numbers and work backwards, you will find the Scr you need, to achieve that "decent" DCr.

If you leave your Scr alone as delivered from the factory,and install a bigger cam with a LATER closing intake angle, this is guaranteed to be a low-rpm disappointment. And you will have to bandaid your combo with a higher stall TC, and sometimes, more rear gear.
If this sounds like a foreign language let me walk you thru a few examples.
Lets take an 8.0 advertised Smog-era 318LA, that has a stock HFT cam advertised at 240/248/112 (IIRC), Lets work out the whole picture, I get;
240/129/123/248/20, Ica of 51* and effective overlap of 18*
(intake/comp,power/exhaust/overlap)
Ok so lets install this cam and set the installed centerline to 111*, and at 800 ft elevation, the Wallace says;
Static compression ratio of 8:1.
Effective stroke is 2.84 inches.
Your dynamic compression ratio is 7.00:1 .
Your dynamic cranking pressure is 133.00 PSI.
V/P (Volume to Pressure Index) is ..............................109
read about VP here V/P Index Calculation
In a nutshell VP is a measure of sub 3200 performance that is sorta relatively comparable across all sizes of engines. So a 318 at 109 is gonna feel like a 360 at 109, etc.
Ok so now, you already know what a 318 at 109 feels like, and you certainly don't want your 318 to be any doggier than that, right.
So with no other changes, say you install a Mopar 268 cam with an Ica of 64*; and what happens? I'll tell you, the VP drops like a rock to;
Static compression ratio of 8:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 6.43:1 .
Your dynamic cranking pressure is 118.36 PSI.
V/P (Volume to Pressure Index) is ............................... 88
that is slanty territory right there. If you have a manual trans, you will need 109/88=plus 24% more rear gear to break even in performance at below possibly 3500rpm!
With an automatic, you will have to jump up the stall, possibly also 24%.
Why did this happen?
Well look at the Dcrs, it dropped from 7.0 to 6.43.. Let me jump up the Scr until I get back that 7.0 with the 268 cam.

Static compression ratio of 8.75:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 7.01:1 .
Your dynamic cranking pressure is 133.26 PSI.
V/P (Volume to Pressure Index) is ................ 99
Now you see that the VP has climbed up a bit, but still is weaker than the stock 318.Also the pressure is just 133 so we have lots of room (up to 160psi say, with open chamber heads) to pump it up. Lets take it to 155, so we can burn cheap gas.

Static compression ratio of 9.82:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 7.84:1 .
Your dynamic cranking pressure is 155.03 PSI.
V/P (Volume to Pressure Index) is............................... 115
There ya go; 155psi, and a Dcr of 7.84, and a VP of 115 which is now 115/109= plus 5.5% higher than the stock 318. NOW you got yourself something to work with.

But hang on a sec, I specified an Ica of 64* on that 268 cam , cuz that is ABOUT what comes on the Mopar 340 cam. And the .050 for that is 228/235/114.... and a 228 cam might powerpeak at about 5100rpm, which with 2.76s is maybe 70mph at the top of first gear..... is that what you want?
Furthermore, if you could make the same power at a lower rpm, would you like that? This is where Wormrider's 200/200 spec come in.
Furthermore, if you could get the same power with less advertised duration, would you like that?
I know I would. This where you toss the HFT cam away and get yourself a Solid.
Lets say the fat 200s allow a 263 cam, and lets say the swap to a solid allows a 258 cam. I mean I'm just tossing numbers out there.
So this solid-lifter cam now, lets say it has the following advertised specs
258/123/121/262/44/42Effective and Ica of 57*
This is a whole different build now.

First, lets put the Scr back to 8.0, and I get
Static compression ratio of 8:1.
Effective stroke is 2.72 inches.
Your dynamic compression ratio is 6.74:1 .
Your dynamic cranking pressure is 126.29 PSI.
V/P (Volume to Pressure Index) is ..........................99
Hey that's looking pretty good, lets bump the pressure up again to 155
Static compression ratio of 9.35:1.
Effective stroke is 2.72 inches.
Your dynamic compression ratio is 7.85:1 .
Your dynamic cranking pressure is 155.29 PSI.
V/P (Volume to Pressure Index) is .................... 122
Wow lookit that the V/P is up to 122, And the .050 will be down some, bringing the power peak down with it, but because the 200/200 is fat, you may not lose any power at all! This is the point Wrmrider is trying to make.
With a VP now of 122, you can use whatever stall and gears were behind the 318 but now with INCREASED sub-3000rpm performance.
And finally; it may be a bit cheaper to increase the 318s Scr to 9.35 versus 9.82

Just for the heckuvit, lets install closed chambers on that 318, decrease the Q to .040 or less, and pump it up to 165psi
Static compression ratio of 9.8:1.
Effective stroke is 2.72 inches.
Your dynamic compression ratio is 8.22:1 .
Your dynamic cranking pressure is 165.15 PSI.
V/P (Volume to Pressure Index) is ............................129
wouldja lookit that VP now 129!, that is 129/109= plus 18% stronger than stock. The penalty is that you will have to run 91gas or better at WOT. But think about it;
18% better VP is like adding 18% rear gear, say from 2.76s to 3.23s, or from 3.23s to 3.73s; to the stock 318. Yur gonna notice that punch.

To be clear; this is an example of what you can do;
and specifically with those very nice pages of data that Wrmrider is publishing, as regards the 200/200 numbers.
This is in no way a recommended build. And personally, I would never install any 268 cam in a 318, with open chamber iron heads, for street use, nor any 114LSA cam. And the reason is this; with just 107ish degrees of power extraction, the Mopar 268/276/114 sucks gas bigtime. Or rather, there is a lot of energy still in the expanding exhaust gasses when the valve pops open; energy that could have been used to propel the vehicle, but that all goes to making noise instead.

OK for the one guy who wants to know; what about alloy heads on a 318 with a 268 cam. Here is what I would do
Static compression ratio of 11.2:1.
Ica of 64*/ still 800ft
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 8.91:1 .
Your dynamic cranking pressure is 183.78 PSI.
V/P (Volume to Pressure Index) is 136
I have a manual trans, with NO TC to help get off the line. So, for me, VP of 140 is where the fun begins. missed it by that much,lol.
See what I mean about the 268 cam? the Ica of 64* is just too much for a 318, even at 11.2Scr!

>Also remember that VP importance diminishes with rpm, and a 3000stall just about nullifies it. So, I mean, if you cannot reasonably get to the Scrs that I have indicated in this study,remember that a high stall gets you past the importance of VP.
>But if you have a manual trans, most of the time, you will be operating in that sub 3000/3500 rpm range, And EVERY SINGLE TIME YOU START OUT from zero mph, VP will be very important.
> also remember that at WOT,as the rpm rises,your cylinders are gonna start filling to a denser air charge, and at some point, between maybe 3000 and 4000 rpm, you may have to be careful with your PowerTiming to avoid detonation, on account of that 11.2Scr is getting real close to the line.> but again, I wouldn't run that 268 cam in a 318 on the street, period. I would sooner get me a bigger engine, to run a smaller cam, for the same WOT power AND a stronger bottom end. Oh wait; that is what I did,lol. Here is 360 with a 360 2bbl cam and 9.5Scr
Static compression ratio of 9.5:1.
Effective stroke is 2.95 inches.
Your dynamic compression ratio is 8.00:1 .
Your dynamic cranking pressure is 159.28 PSI.
V/P (Volume to Pressure Index) is ...........................142
See that? VP of 142 without hardly trying.I mean all I did was pump it up to 9.5Scr/8.00Dcr. And the power peak is already in a good place, say 4500@39mph in 2.45 first gear with 3.23s. A footstomp should get both tires spinning.
Happy HotRodding

Edit
Oh but you wanna know about the 268 in the 360?
First at 8.0Scr
Static compression ratio of 8:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 6.46:1 .
Your dynamic cranking pressure is 119.12 PSI.
V/P (Volume to Pressure Index) is ........................100
Not too impressive, the bottom end is weak

optimized for Iron heads and 89 gas
Static compression ratio of 10:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.01:1 .
Your dynamic cranking pressure is 159.55 PSI.
V/P (Volume to Pressure Index) is ......................134
Wow, lookit that jump in VP, impressive

And optimized for alloy heads and 87E10
Static compression ratio of 11.2:1.
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 8.95:1 .
Your dynamic cranking pressure is 184.87 PSI.
V/P (Volume to Pressure Index) is .......................156
there ya go; feels like a 440Magnum of yesteryear...... up to say 3500rpm . Vp of 156 is actually borderline excessive. That's about what my 367runs and 295s don't stand a chance. But it is so sweet to take off with; basically I just blip the throttle a lil in Neutral, then let the flywheel launch me with a dump it and go kindof deal.