Hi Dan!
Friend;
almost any high lift flat-tappet cam is gonna be "hard" on the stock valvetrain, and often noisy, as compared to the stock parts, which were mostly dead quiet.
How "hard" will depend on how extreme you go, and the willingness of the parts to play nice together, and the level of competency in the assembly of the parts.
The last time we talked, IIRC you just wanted a snappy DD.
At the power-level you were interested in, at that time, this won't be an issue; if the rest of the combo is even just half-decently matched.
In a DD, or in a usage as you described, the absolute power is way less important than having good torque when and where you need it; and to deliver that, with a 318/auto, is gonna be almost entirely dependent on the convertor-stall and gearing.
Absolute power does not happen until all the selected parts come into harmony, which is gonna be an rpm range of about 800rpm, centered somewhere between 4200 of the stock 318 cam, to around 5000 if a cam around factory 340 size. The cams in question here are about 248 to 268 degrees of intake duration, thus a range of 20 degrees. The difference between any two cam sizes is about 7*, so 20 degrees is a range of 3, plus the starting place, so the choices are four, the usual choices being; 248,256,262,268; each cam peaking about 200 rpm higher.
With a stock 318 convertor stalling around 2000 rpm, AND the compression ratio remaining unchanged, and with NO OTHER changes, each cam bigger than 248* is most likely to have LESS take off torque. This means, the power will also be down. The usual cure for this is a higher stall.
The thing is, for a mild 318, and at rpms less than about 2800, each bigger cam is gonna need about 200 rpm more stall just to stay even with the torque of the stock 318.
So even if you keep pace with ever higher stalls, the sub 2800rpm power is hardly keeping pace and the low-rpm performance level is not increasing by much. But at least it's not tanking.
So for a DD that spends most of it's life below 3500; and with only an occasional excursion to maybe 4000, which in Second gear with 2.76s is already over 70 mph; going to a 5000 rpm cam with little or no power increase where you need it below 3500, this is IMO not a good way to go.
The DD needs more power in the operating range that it will be driven in. For a given engine, a bigger cam, by itself, is NOT a good idea. The better idea is to
better match the current engine to the intended application; or, to increase the cylinder pressure, to match the new cam.
Increased cylinder pressure, increases power, EVERYWHERE in the rpm-band.
Here's something that might help you;
Say your engine makes 265 ftlbs of torque at 2000 rpm, going to 290 @2800. This is a realistic progression. Say you have a 2000 stall and an A904, and 2.76 gears. So then, at take off, not including what is going on inside the convertor, to the rear axles is going;
265 x 2.76 x 2.45= 1792 ftlbs.
Lets say all you did was increase the stall to 2800, and swapped in some 3.23 gears. This gear swap by itself is plus 17% . The new number would be;
290 x 3.23 x 2.45= 2295 ftlbs. This is a total increase of 28%
To get the same result, using the 2000 stall and 2.76 gears, but with a bigger cam;
2295 ftlbs/(2.76 x 2.45) = 339 ftlbs . And 339/265 is plus 28% again. A normally aspirated 318 will never ever make plus 28% at 2000 rpm, with no other changes but the cam. Never! Well unless yur coming back to stock from a way too big cam lol.
So then, friend, as I have said before, since, with a bigger cam, you are gonna need gears and a higher stall convertor anyway, you might as well decide on those first, and bolt them up; just maybe, your current engine-combo will be crispy enough for you. It really depends on what is already in your car, and how much hiway driving you intend to do.. For a city car a 2800 and 3.91s is dynomite. That will wake up any old oil-burning smog-era 318, including a 2bbl single exhaust old wheezer. lol Lets say that old wheezer can still make 265 ftlbs @2800; then
265 x 2.45 x 3.91= 2538 to the axles. This is 2538/1792= plus 42%
see what I mean? No cam, by itself, will touch that Plus 42% increase.
Hope this helps
