Many have already explained the larger lifter bore is an advantage and not a myth, but shelf cams are never going to push the envelope as far as acceleration etc. They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired...
OK, fair to an extent...strangely enough somehow the Chevy and Ford grinds end up with the higher lift lobes though...presumably out of the very same lobe catalog I have here, so why isn't CompCams putting the higher lift lobes on Mopar cams???
I mean like you said:
"...They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired..."
...so what is the reason for pairing the lower lift lobes for our small block engines? Is it poor head flow? Is it bad geometry??? That's the depth of an answer I'm looking for...
Bottom line being: the "shelf cam" argument here holds no water, as I just pointed out the other guys somehow end up running those lobes...so what gives? That's really what my question is about...would you not expect any manufacturer to want to optimize their sales regardless of what engine their product goes into? Makes no sense to me to want to sell less product...after all, if more lift was a bad thing we'd all be running our stock cams! LOL
Don't confuse total lift with the lift rate of the lobe. Two seperate things. The reason all the cams for Chrysler's have low lift is the idea that the port breaks over at about .450 lift. I can make it break over much lower than that. I can also move it up, or at least flatten it out. Put an intake manifold on and it changes everything.
I run as much lift as I can get for the valve gear. I'm running (on the street) a lobe that is 281 on the seat at 255 at .050 so it's pretty close to a Comp MM lobe. With a 1.6 rocker I net about .606 at the valve. It isn't hard on parts. It will idle clean down to 700 but I don't idle it that slow. That's hard on parts. I let it idle at 1000 and it's not an issue.
As to why the manufacturer doesn't optimize lobes for a Chrysler is there is NO MONEY in it. Most guys to this day STILL buy a cam out of a catalog or worse yet, take a poll on a forum and Joe blow runs cam XXYD in his jalopy and it's the cats ass even though Joe has never done any testing. So they have to have a cam today and they buy that crap. Honestly, 98% of the guys out there won't ever know the difference.
It's economics. Simple money math. There are so many companies that will grind a custom cam with a .904 lobe on it for you there is no sense in every buying an off the shelf cam. But, you have to convince the guy on the phone why you need a faster lobe. I bought my cam from Jim at Racer Brown and before he used those lobes we had almost two hours on the phone and flow sheets plus a drawing of the cutter I used used for the valve job.
