Here's some numbers OP
to help you understand the low-rpm issue, with a 340 and a 284/114 cam in an 8.2Scr 340.
I inputted your 284 cam as a 114LSA, so in at 4* advanced, the ICA would be
72*, and I inputted
800ft elevation.
Static compression ratio of 8.2:1.
Effective stroke is 2.38 inches.
Your dynamic compression ratio is 6.17:1 .
Your dynamic cranking pressure is
111.76 PSI.
V/P (Volume to Pressure Index) is
82VP
Notice the cylinder pressure and VP, are both very low.
read about VP here;
V/P Index Calculation
Here is a stock 225slanty, at the same compression ratio, but with an ICA of 48*due to it's much smaller cam
Static compression ratio of 8.2:1.
Effective stroke is 3.51 inches.
Your dynamic compression ratio is 7.32:1 .
Your dynamic cranking pressure is
141.33 PSI.
V/P (Volume to Pressure Index) is
93VP .
Notice the pressure is up,partly cuz of the earlier closing intake, and notice also the significantly larger VP. The slanty should actually feel more powerful,car for car, in the lower sub-3000 rpm area.
SO VP is the thing you need to do something about.
Here is YRs proposal of retiming the cam to 102. This would get you an ICA of 64*, so
Static compression ratio of 8.2:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 6.58:1 .
Your dynamic cranking pressure is
122.19 PSI.
V/P (Volume to Pressure Index) is
97VP .
Notice your engine picked up 11psi and 15 points of VP.This is a very significant improvement of 18%. This is about as good as it gets with the parts you currently have.
Ok so lets go back to the original install, and boost the stinking compression up
Static compression ratio of 10.5:1.
Effective stroke is 2.38 inches.
Your dynamic compression ratio is 7.82:1 .
Your dynamic cranking pressure is
154.50 PSI.
V/P (Volume to Pressure Index) is
113 .
Ok now you got some pressure, and can still burn 87/89. This is about as good as it gets with that cam and iron heads.
Notice the VP jumps to 113. From the original 82 this is 113/82=38% improvement. So now it's taking off like a 318.
Ok but say 318 take-off sucks to you. Lets put a proper IMO, street cam in there and a matching compression. I like the 268/276/110, in at 108
Static compression ratio of 9.8:1.
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 7.93:1 .
Your dynamic cranking pressure is
157.42 PSI.
V/P (Volume to Pressure Index) is
126
Ok this will burn 87 most of the time, but might want 89/91 at WOT.
Notice the VP is now up to 126; a 54% improvement.This is IMO a real nice balance of low-rpm torque , a fat midrange and reasonably good top-end... for a streeter with 3.55s
Ok one more, if your pockets are deep and you can afford some aluminum heads. This is still with the 268/276/110 cam, but with the Scr pumped up for the new heads . I have burned 87E10 in my 367 with this pressure,
Static compression ratio of 11.3:1.
Effective stroke is 2.61 inches.
Your dynamic compression ratio is 9.11:1 .
Your dynamic cranking pressure is
189.24 PSI.
V/P (Volume to Pressure Index) is
152
Notice the VP is up to 152 now,an 85% improvement, in low-rpm operation, where you probably are some 80% of the time, up to about 3500rpm. The 268 pulls strong to about 5400,then levels off, and with the Eddies I got, I force her to 7000 all the time.
I know, I know, I just included the last one for comparison.
A 152VP is about what a stock 1969 440 Magnum pulled, just so you know.
