Tommy
It is very easy to kill the bottom end performance with a slightly too-big hydraulic cam. Then you have to get a bigger TC and maybe more rear gear too.
If you are gonna cam it, I highly recommend a small solid lifter cam with a tighter LSA to maintain the same or similar ICA. Without a compression increase,your bottom end performance depends on that ICA
Your oem 1974 LA 318 was advertised with an 8/1 compression ratio, and came with a 240/248/112 cam.In at split overlap and at 500ft elevation, that would yield an ICA of 50* and pressure of
133@109VP. Read about VP here
V/P Index Calculation
You already know what this feels like. Keep your eye on the pressure/ PV as I continue.
Say you put an oem 360-2bbl cam in there with specs of 252/260/112: The ICA moves to 56* and pressure to
126@100VP .
Or say the popular 262/270/110 cam: the ICA goes to 59* and pressure to
123@95VP .
Or the ever popular 268/276/110: the ICA to 62 and pressure to
119@90VP .
Are you seeing the trend here? The ever bigger cam trades away low rpm performance to get high rpm power, not the greatest thing for a streeter.Especially a small displacement one. a VP of 90 is down in slanty territory.You wouldn't like that.
Now it's true you can get the low-RPM performance back with a hi-stall TC. And you can get the low-SPEED performance back with more rear gear. But that costs money.
But here comes my point; You can install a fast-rate solid-lifter cam with a tighter LSA and keep most of that low-RPM performance, while simultaneously getting some hi-rpm power as well.
Say you found a 256/262/106 cam, with an ICA of 53* the pressure might be
129@104VP, so that is climbing back up. (Compare that to the original 133@109VP.) This cam will mostly preserve your current low-RPM performance
while yet increasing the hi-RPM power. I'm guessing this theoretical solid lifter cam might be around
[email protected],after lashing, compared to the hydraulic 268 also at
[email protected]; but remember that the latter cam only made pressure of 119@90VP. Furthermore, with the pressure/Vp restored to near oem levels, you could keep your current TC and gears...... at least for awhile,lol.
Of course the down-side is periodic lash adjustments, like once a year. The upside is better rev control so with the right springs, you can rev it till you can't stand it anymore; well over 6500 if you have done the oiling mods.
With this 256/106 cam the .050 spec difference to oem is about 29degrees so it might be considered 4 sizes bigger than the factory 240/112 cam. That is a lot.
I tell you this to try and save you a lotta money; the wrong cam comes with the additional one-time costs of TC,gear,headers, and a free-flowing exhaust; and the continuing cost of lousy fuel mileage.
On a side note, the 318 does very well with 4.10/3.91s and a .69 overdrive, as a streeter, even as a stock-cam,2bbl,single exhaust, power house.
Happy HotRodding
