Comp's XE Cams

AJ/FormS said
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.

You posting this like it's a 100% fact, be nice for you to find some dyno evidence to support this, the basic premise is true low cr, bigger cams, smaller displacement, higher gears, low stall all can hurt performance especially low end, but the question is where are the lines and or acceptable compromises, 318willrun 318 duster kind of flys in the face of what your saying his car is basically everything you say not to do.

Now these dyno of 318's don't prove either of us right or wrong since they don't all go down to 2000 rpms so there's guesstimating, first in these 7 examples one being a dead stock 2bbl low cr 318 with headers makes peak torque at 2000 rpm of 292 lbs-ft all the other six make around 340/350 lbs-ft at 3000 rpms with a range of cams from 218 to 247 and all but one with about 10:1 cr, the one that has low cr is the stock long block 318 with 4bbl headers and a comp xe262h. (the ones not shown are the 3 400 hp and 1 425 hp 318 builds)

318 Stock low cr long block with headers vs same with 4bbl and xe262h vs same and carb spacer.

TORQUE SUPERFLOW 901 DYNO-TESTED AT WESTECH
RPM	BASE	MOD 1	MOD 2
2,000	292
2,500	287
3,000	287	338	336
3,500	272	335	340
4,000	248	326	330
4500	218	309	319
5,000	188	285	296
5,500		250	258

HORSEPOWER SUPERFLOW 901 DYNO-TESTED AT WESTECH
RPM	BASE	MOD 1	MOD 2
2,000	112
2,500	137
3,000	164	193	192
3,500	182	224	227
4,000	189	248	252
4,500	186	265	274
5,000	179	271	282
5,500		262	270

Now below is a built for the engine master competition but is a 477 hp 318 that makes 337 lbs-ft @ 2500 rpm with a 247 cam and makes the most at 3000 rpm, even if you drop a good percentage off if it's was running stock cr compared to 10:1 cr, reason I post it, it's the only other 318 that shows anything happening under 3000 rpm.

On The Dyno DTS Dyno Data Performance Crankshaft 323CI Small-Block Mopar

RPM	TQ	HP
2,500	337	161
2,600	350	173
2,700	357	183
2,800	357	190
2,900	356	196
3,000	351	201
3,100	345	204
3,200	339	207
3,300	343	216
3,400	356	230
3,500	371	247
3,600	385	264
3,700	396	279
3,800	404	292
3,900	410	305
4,000	415	316
4,100	418	327
4,200	420	336
4,300	422	345
4,400	421	353
4,500	420	360
4,600	421	369
4,700	425	380
4,800	426	390
4,900	427	398
5,000	427	407
5,100	427	414
5,200	426	421
5,300	425	428
5,400	423	435
5,500	421	440
5,600	419	446
5,700	417	453
5,800	415	458
5,900	412	462
6,000	407	465
6,100	401	466
6,200	397	469
6,300	393	471
6,400	390	475
6,500	386	477

AJ/FormS said
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.

Actually more like 292 vs 287 lbs-ft

AJ/FormS said
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.

The cammed low cr is making 338 lbs-ft at 3000 rpm plus 5 more bigger cammed 318,
The biggest cammed 318 is still making that at 2500 rpm but what do the rest make by 2000 rpm same, more, less, a lot less, enough to kill 2000-2500 rpm performance ?? I Don't really think so, but yes there no proof that they do or don't, guess it's how you guesstimate what's going on there.

I have a hard time believing they all take a huge drastic down turn under 3000 rpm and are being massively smoked by the stock cam at 2000 rpm especially factoring that at 2000 rpm for every loss of 2.7 lbs-ft = only a loss of 1 hp, it would take a loss of 27 lbs-ft (292 vs 265) to kill 10 hp at 2000 rpm (111 vs 101). Not saying that don't matter at all but by 3000 rpm and on the cammed engines are making more hp than the stock does at peak hp, don't you think that has a more dramatic effect on performance?

AJ/FormS said
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

Like usually you'll ignore the possibility that there huge holes in what you're saying and won't readjust in anyway, which Is a shame I like you're basic premise.