318 Port match heads to Performer RPM Intake
The simple answer is this
After the cam is in, and the heads are on; but before the intake goes on, do a compression test. Here's my opinion;If you have
120psi and less, this is a nightmare
125 to 130psi is really doggy
130 to 140 is still soft and needs both a hi-stall AND gears
140 to 150 is getting somewhere, a 2400staLL is barely adequate at the 150 side, and 2800 at least on the 140side and she'll still want 3.23s or better.
150 to 160 is where you want to be. She still burns 87 on the 150 side and might want 91@WOT on the 160 side. 160psi will allow a 2400 and 3.23s
165 is about the limit for iron heads, but I wouldn't go there with open chamber heads.
The Wallace calculator is predicting, see above,
130psi in a true 7.8 Smoggerteen, and
about 160psi in a true 9.2 First-gen hi-compression pre 73 318LA.
As you can see, that cam can get you into trouble in a heartbeat.
It can make reasonably generous low-rpm power at hi pressure, but when it gets stuck with 7.8Scr, it takes a lotta lotta rpm to wake up, and then it's all over.
For example 3500 with 3.23s is about 32 mph, and good luck making both tires spin, with the factory TC.
3500 with 2.76s is about 38mph, and no chance at all to spin the tires with the factory TC.
The power of that cam peaks at maybe 4500/4600, and then drops off fairly rapidly so you might shift at 4800. That will give you a powerband of 1300rpm or so, with that low pressure combo, if you end up having that. ..... but your 1-2 split in the 904/727 is .59, so it will drop you Rs from 4800 to 2800, and there you are, with the poor 318LA stuck trying to claw itself out of a hole that starts at (with 3.23s)44mph and begins to wake up at 55, peaks at around 70 and the shift comes at 75 mph. Good for a passing gear, but not much else.
The factory 318 cam was a 240/248/112. And in at 108 the Ica would be 48*, and the 8.0 nominal 318LA (more like 7.8 it's been said) made about 136psi with that. That's your measuring stick.
The Whiplash, in at 104*, has an Ica of 54* (estimated by me) and is predicted to make just 129psi
That is about a 5% powerloss at low rpm, and all the way up to 3000 to maybe 3500 with that combo. To compensate for that, you would need 5% more rear gear AND 5% more torque at take off, Which means a higher than factory stall, to compare apples to apples.
If your teener, before the cam made 210 ftlbs at 1800 stall, it might now need a 2000TC just to make the same take-off.
Whereas a compression ratio boost from 7.8 to 8.1 gets your 136psi back, and now she is with the Whiplash cam taking off just like it used to, and using the same gears. But is that what you want, just to be the same?
Ima thinking you didn't just spend a wad of cash to go slower to 32mph, and not go the same either. And 32mph assumes 3.23s!
What Hughes is saying, is that cam has 48* of overlap, like a factory 340cam(44*),So you get the 340sound;
but it is about one cam size smaller than a 340 cam at advertised: 260*(estimated by me) versus 268*, so it won't be as doggy as a 340 cam tends to make a stock 318 be.
What is not mentioned is that the 260 cam is about 260less 240=20 degrees, and 20/7 = 3 cam sizes bigger than a factory 318 cam
Typically one cam size drops your cylinder pressure about 3psi in this range so, with 3 sizes, I'd expect 9psi ; whereas the Wallace predicts only 6, which is due to the switch from 112LSA to 109. Good deal.
So the bottom line is,
With no other changes, the Whiplash will not turn your 318 into as lazy a dog as a 340 cam would, but it WILL be lazy all the same.
So then they tell you to change the stall and gears so you won't notice the doginess so much.
In other words, this cam will cost you a TC and gears in addition to the cam purchase. I'll guess close to or over $1000 additional costs, installed.
For a G-note, you could put the proper pistons in there, and maybe have enough left over for some decking, and end up smoking both tires (with a SG of course), commensurate with what the idle-sound is saying, assuming 3.23s and a 2000TC to start with.
But with 2.76s and a 1700, you's still have to wait a bit to find some power.
So ,IDK it all depends on where you are starting from. If you have to buy a a TC AND gears then just make sure they will work with the lazy pressure, after all is said and done.