I tried a test with the compcams software just to see what would happen and now I will ask here as there was no a sure soulution to the question .
I tryed to do this with everything being equil and just changing pistons and cams , Same heads and even swap of intakes . I will admit I do have a limited knowledge but this is how we learn
12:1 compression = 580 hp
7:1 with a weiand 144 and 10 lbs of boost (net compression of 12:1)=589 hp
8.5:1 with 6 lbs of boost ( net 12:1) came up at 580 hp also
The slight difference in hp outcomes I am sure is from having a limited selection of pulley ratios for the blower and not being able to enter the exact ratio that I needed
It makes it difficult for me to see the advantage of the supercharger , will the supercharged motor Rev up faster ?
When building a supercharged motor is there an advantage to running lower compression with more boost over a little higher compression with less boost to get the same net compression ?

one advantage with the supercharger and a compression lower than 12:1 is you can still buy gas for 3 dollars a gallon versus 15 dollars. twin turbo is my choice , it just seems to be a little more streetable.

I thought I would just bump this back to the top , I am suprised that I have only had one reply and no answer to the questions

I know people love to hate it but you could easily run E85 on 12-1 compression, its $2.89 a gallon right now where I live.

Jordon

A super charged engine will rev a lot quicker. It is better to run lower compression and more boost for longevity. You should also make sure you run a boost retard, such as MSD's that you can make adjustments to help eliminate detonation.

Heres how it goes in my mind.

supercharger pros

-smaller cams build same amount of horsepower and likely more torque across a larger rpm range

-this leads to a more streetable engine that consumes less fuel and the availability to run pump gas

-more torque down low allows the use of longer gears, which inturn creates for even better engine/tranny longevity and mpg increase

-and then theres aesthetics the supercharger creates, everybody loves the look of a blower on top of a v8

supercharger cons

-it takes horsepower to turn the supercharger

-it adds weight to the vehicle

the blower and a reasonable compression ratio will be the most streetable. You don't have to run a big crazy cam or race gas. With 12:1 compression, you will need race gas. Of the combos you posted up, I think the 8.5:1 ratio is your best bet with a blower. When in low RPM's the blower is not yet producing boost, but you still have reasonable performance with the 8.5 c.r... When under boost, yes the effective C.R. will be higher, but as boost comes up, the rpm's come up as well and that's why you tune the advance curve to bring the timing in to compensate for this.

If your static C.R. is very low, like 7:1, your engine is going to be a total dog until it starts producing boost... go for a C.R. in the 8-8.5 range for a supercharger... and then run as much boost as you can get away with on pump gas without detonation. You can get away with a little more compression if you're running aluminum heads because they dissapate heat better and tend to resist detonation better.

Once you get the combo running, tune by checking the plugs and making adjustments accordingly. You will have to run a blower on the rich side... one thing you do not want is to have the engine going lean under boost... also running rich will help cool the engine. The way to acheive max performance is dial it in right up to the point of detonation... and then back it off. You want to stay out of detonation, but right below that point is where the engine will operate the best.