Bore, stroke, rod length,Scr, Ica, and elevation
then go here,
Wallace Racing: Dynamic Compression Ratio Calculator
and pay close attention to the V/P, which you can read about that here
V/P Index Calculation
to get a picture of where you are starting from , plug 7.8 in for Scr and 50* for the Ica,These are the specs for a stocker with a 240/248/112 cam, in at 110....
plus the basics; 3.91x3.315, 6.123rods, and your local elevation; 300ft IIRC. I get 132psi@
109VP, and you already know what that feels like.
I took the liberty to max out your compression for this cam, with a bore job and hi-compression pistons and retarded the FACTORY cam to a Ica of 53* so you can rev it a bit. This is about the max you could run on pumpgas. I get
Scr of 9.25 @161psi @
132VP @7.97Dcr.
This would make a real stump puller, with fabulous first gear performance. and tons of grunt in second at say 30 to 45 mph just where you need it.
With 2.76s and the 2800TC, you won't get any better, to somewhere between 45 and 50 mph.
As a comparison this
132VP is more VP than a factory 340(
128)calculates to , more than a factory 360(
121)calculates to,and even a 440Magnum calculates to just (
136) with the 4bbl cam.
And we haven't even talked about the fuel mileage improvement,or what the 4bbl and headers are gonna do for you. These V/P numbers are most valuable to know, from a factory stall to in the range of 3000 to 3500, after that the combo better be making power elsewhere cuz the VP advantage has diminished to nothing. That factory 240 cam is done pulling around 4500rpm. That doesn't mean you have to shift it there, in fact with the standard TF ratios, the 1-2 split is 59.2%, so for low-ET this combo might need to be revved yet higher, perhaps 5000 or a bit more.
And for anyone reading this that has a manual trans, you know how much time you spend from 1600 or so to 2800 or so. For you guys VP is really really important. If your combo is doggy in there, I know you ain't happy. And nothing sounds worse than a Mopar impersonating an old Mustang, having to slip the clutch out so it don't stall, and then rev it to near 4000 to find some torque in second; Man, I would be so embarrassed . With VP like this, and typical street gears,and street flywheel,you can just dump it and go. I'm not kidding. As a comparison my 367 calculates to
156VP and spins 295s/325s to waaaaay past the speed limit. I have to lift at 65,lol. Actually I have to cuz that is 6900 with my gearing,lol. Oh! we're not talking about high rpm in this chat,sorry,lol.
Ok so with my 10.97 starter gear, it really is a blip the throttle and slip it out, without any gas pedal, deal. It was pretty similar with a 9.44 starter gear. But with 3.23x2.66 it needed a bit of gas-pedal, and/or easy on the clutch pedal. This is where big VP pays off;throttle response and low-rpm driveability and the ease of initiating tirespin without racegears. 156 is a lotta,lotta VP. 132, as you can see, is quite a bit.
