The 1-2 split of the 3.09-1.92 combo, with my hi-pressure 367 works great.
The Dcr/pressure/V-P in my current combo is about 8.8/180/156
It has been to 9.3/195/169 with a smaller cam.
IMO
with a 340/3.23/2.66 street-combo, pressure is gonna be your best friend. I would gladly sacrifice power at 5500 to get over 3000 ftlbs into the axles at zero mph.
Here's how you work backwards;
From empirical testing. I know that 3000 ftlbs into the axles is about where I wanna be to bust a pair of 295/50-15s loose and roast them. Skinnier tires with no traction-aide, will bust loose with less. Therefore; 3000ftlbs is my target.
3000/(3.23 x 2.66) =349 ftlbs at the crank. If you want crisp take off at WOT, yur gonna have to rev up your engine until you find that amount of torque. Maybe your 340 will make it at 3000; but maybe not until 3500, it depends on the combo of parts you use and specifically on how much pressure it builds. Heaven help her if she can't get there until 4000.
FYI; My 367 makes that almost right of idle.
But say you swap out that sick 2.66 low for a 3.09; Now the numbers are 3000/(3.23 x 3.09)= 300 ftlbs. any 340 should be able to make that at under 3000 rpm at WOT.
But say you don't want have to go to WOT, all the time just to bust them loose. so say you want to be able to do that at part throttle, say at 240 ftlbs, then
3000/(3.09 x 240)= a 4.04 rear gear
But say you want to keep both the 2.66 and those 3.23s. Then
3000/(3.23 x 2.66 )= 349 ftlbs, but you want those to show up at 2200. Well your 340 is gonna need a lotta pressure to do it.
With an auto trans, you could depend on the TC to help the engine, but you don't got no TC so your engine has to do it all-motor style.
So then, how do you build a 340 to make 349 ftlbs at 2200?
IDK but I can guess;
1) it's gonna need a lotta pressure
2) Pressure is your friend
3) It all starts with, you guessed it; a high-pressure design
Ok so what is a high pressure design?
Well you can make pressure a few ways;
1) with cubic inches
2) with a High Scr design
3) with an Early closing intake
$) with forced induction.
However, you have to stay within the limits of the fuel to resist detonation.
Let's say you had a smog era 318 at a true Scr of 8.0, and the stock 240/248/112cam in it, which is installed 4* advanced and in at 108. The Ica becomes 48*, and so, the Wallace predicts
at 800 ft elevation; 7.1Dcr/136psi/113 V/P
Lets install that same cam into a 340 still at 8.0 Scr. The Wallace predicts 7.1/136/121 V/P, an increase of 7%, which is the exact difference in cubes from the 318, measured in percentage; therefore a 440 could be expected to produce
440/318x 113=156V/P and that is exactly what the Wallace spits out, still at 8.0 Scr and 800ft elevation.
Now a V/P of 156 is pretty nice.
So that is how Scr plays out
Lets go back to the 318 and start playing with the Ica
First the stocker at Ica = 48* ; the Wallace predicted 7.1Dcr/136psi/113 V/P
Lets go to Ica of 58, which is just tickling performance.the numbers fall to
6.7 Dcr/125 psi/ 97 V/P and so the bottom has fallen into the basement.
Lets add 5 more degrees to get an Ica of 63*n which is a typical performance cam. The numbers fall again to
6.47/119/89 V/P which is tickling on slanty terrible-tory. So that's what the Ica does with no other changes, it kills the bottom end.
To get the V/P back up to 119, of the stocker, with that final Ica of 63*, the Scr would have to be jumped up, to 10.0 .... to have the sub 3500 rpm performance to be about the same as ... stock. And where do you ythink a 318 street car spends the vast majority of time? Yeah I'll bet under 3500. So don't put a big cam in a stock 8.0 Scr 318. Not ever.
So now we get to the 340
Say this one is already at 8.73Scr, and has a stock 340 cam in it with an Ica of 64*. The Wallace kicks out;
a Dcr of 6.99/pressure of 133psi/ and V/P of 105; which is back in the basement; under no circumstances would I build one of those. Ok but say you really wanna use that stinker of a pressure robbing cam, and yur still looking for 349 ftlbs at 2200rpm. I'm gonna say; that will never happen and the Scr still be low enough to run pumpgas, But, let's work the calculator anyhow. At 10.0 Scr the Dcr is topping out at 7.99, the pressure is topping out at 159psi, and the V/P is up to a whopping 126. This is less than a stock 5.2 Magnum, so that is as much as you can expect with that cam and best pumpgas. Will it spin the tires? yes I think so, but a Doubt it will make 349 ftlbs at 2200, so yur gonna have to rev it up to get the numbers.
So in that iron-headed combo, the bottom-end is still seriously soft; and keeping it a 340, and naturally aspirated, typically, you only have one other choice, which is to slam the intake closed sooner.
More coming