I like your thinking
It took me a few seconds to figure out your data , but I get it.
What I like about this kindof stuff is that a guy can better match the power requirement to the idle quality and the Scr can be sacrificed in favor of extraction..... cuz the pressure can be better manipulated with the earlier Ica. This makes for a more enjoyable streeter with better manners and the potential for better fuel economy.
The fuel-economy thing is gonna get more important into the future as the cost of gasoline keeps going up.
Consider the old 292/292/114Mopar cam, in at 110 the numbers look like;
292/292/114+4/64 overlap(56 effective)/104 compression,96 extraction
With just 96* extraction, this cam leaves a lot of energy in the exhaust, instead of putting it into the driveshaft. Plus to get any pressure from the measly 104 compression degrees, the Scr has to be punched up as high as possible, which for a streeter with iron heads, is not nearly enough, so even less energy is being put into the crank, in the name of using pumpgas.
And for what? hyup the 248* @.050, that gives you a wicked idle..... with a soft bottom end that you gotta bandaid up with a big TC and big rear gears and while that takes the fun factor to a new level,it takes the street right out of the streeter.
And the worst part is that the intake valve doesn't actually close at the mathematically derived 76* Ica, nor the exhaust at the mathematically derived numbers. So what you get is a lousy street engine at the typically chosen 9.5 Scr, that comes with the added expense of TC and gears and rotten hiway economy. What a mess.
But if a guy could get a cam with the same .200 duration, with a way smaller .008 number, and a tightened up for street LSA, that would be the cat's meow.
Looking at your examples of similarly advertised cams, I see .200 durations varying from a low of 111, to a high of 149 degrees. That is a flipping huge range.
I took the liberty of re-arranging your data into two groups of similar durations at .050 to see how this would wash out, here it is;
Group I ......................................... Group II
268/222-143 ...............................270/214-119
264/218-149 .............................272/212-130
272/218-141 ............................... 264/212-128
270/218-138 ................................260/211-126
268/218-136 ..............................
260/210-132
270/217-138 ................................268/210-126
....................................................260/208-128
Lets look at Group I.
Overlooking that the advertised numbers might not all sync from the same base point (for this discussion it doesn't matter);
Look at the .050 numbers; a range of 217 to 222 or very close to a difference of one cam size
Next; the .200 numbers; a range from 136 to 149, or about 2 cam sizes!
Finally, the Advertiseds range from 264 to 272, also about one cam size.
So if yur shopping by .050s, yur gonna run into a chitload of WTH, unless you got yur eyes peeled on the .200s
And I gotta wonder; How many times, have the "tiny" 264/218-149 and the 260/210-132 been overlooked .....Get a load of this baby;
264/218-149. In it's group it is the smallest at advertised and, just 1* from the smallest at .050 yet, nearly a full cam size bigger at .200, than the next nearest listed!
Makes me want to rip the front of my engine off and measure my old Hughes HE3037AL; maybe it really is a hi-intensity........ that might explain my 93 mph Eighth.
But one thing that might throw a monkey wrench into the mix for some guys, is the idle rumble; like of the old factory 340 cam. Some guys just gotta have that. Not me. I'd give it up in a heartbeat for a streetable "hi-intensity" cam.
With what you have shown us now, we need a Group III with 228 to 235@.050....hint.....
cuz honestly, I had a
270/276/110 that was 223/230@.050, and I currently have a
276/286/110 that is 230/238@.050; both very streetable.
But lessee, if I could get 10 to 15 more psi from a similar .200 spec cam; I almost wouldn't care about any other spec,lol. And I absolutely don't care about a loss of idle lope. But I could sure use some more extraction degrees; this 230 cam sux gas real good..
Cuz that's one of the things I'm seeing here; one cam size, per the advertised spec, for my engine is is about 9psi pressure. So if I retard, the faster to .200 new cam, to maintain the 180 psi, then I could trade away some compression degrees, to get some more extraction degrees.
Here's how that might work out; first the current combo, then the new one, then compare to the 292Mopar. (#4 is transferred in from further in the conversation)
1)276/286/110+4/61overlap(58Effective)/116compression/
103 extraction/Ica 64/230@.050/unknown .200
2)268/272/106+1/58overlap(58Effective)/121compression/
117 extraction/Ica 59/don't care@.050/ same .200 as #1
3)292/292/114+4/64overlap(56Effective)/104 compression/
96 extraction/Ica 76*/ 248@.050/unknown .200
4)272/278/108+1/59overlap(58Effective)/117compression/
112 extraction/Ica 63/~234or more@.050/more .200/and back to 180psi
Getaload of that 117*extraction. I bet I can get that into or near 30 mpg in point to point. Pounds the crap outta 103*.Ica moved from 64* to 59* so a higher-vacuum, cleaner-idle, as well. And good news! with the same Scr before and after, the extra 5 degrees of compression should be good for 6 more psi. What the heck am I gonna do with 186 psi. The car already has too much..I know, I'll increase the Intake duration and trade away some pressure for some top-end rush! Lessee; how about
272/278/108+1/59 overlap(58E)/117comp/112extr/Ica63/~234@.050 or more/more .200/back to 180psi; there yago; (Added it to the list.)
Or maybe I'll swap out the 3.55s for 3.23s.... naw!
But wait, I could give up a few more psi; lessee, suppose I hadn't decked my block and left the pistons .007 in the holes...... oh if I had only had these options in 1998 when I was dreaming. Oh wait, I couldda built one of my 340s, instead of a 360 with a gas-swilling 292cam...............
Nothing but wins for me.
Am I on track?
Wyrmrider; thanks for enduring the insults, and bringing it!
