Compression Ratio and Boost Query
IDK anything about turbos, and IDK your answer, except that 25 years ago, I was on the same road that you are now on.
I remember back in the day, a 9/1 318 was advertised at 230 hp/crank, which translates to around 195 rear wheel.
And I seem to remember that 8 psi is likely to double your horsepower.
So at 460 hp/crank how close is a 318 to catastrophic failure? never mind 15psi.?
Whereas by 1973, the Net hp was down to 150hp(maybe 175crank), in the 8/1 engines with crappy timing controls and EGR. 350 hp would be doable.
and don't forget that these small-block Mopars only have 4 bolts per cylinder, and tiny cams, and AFAIK, you can't find a headgasket for a 318-sized bore. Which means that the sharp edge at the top of the cylinder bore, is now a part of the combustion chamber, which can't be good.
And then there's attrition. First the small rear end explodes, then the trans explodes, then the U-joints start shattering. and so on. IMO, there is no budget in this 15psi equation, as one thing just leads to another.
And then, there's the problem of finding traction. Lets not forget, that a 350hp 360 can break traction at 50 mph with just a foot-stomp in Second gear, and if you let that fly and the car gets off-axis more than ~7 degrees, depending on Driver experience and road conditions, that car is/or could already be in trouble.
With the more power, the car become a rocket, and the drum brakes can't slow you down anymore and the stupid thing keeps spinning around in a circle on nearly every corner. How much the more with a turbocharged 15psi 318?
Now, I get that if you re-engineer your 318 for a turbo, as opposed to just bolting one on then, ok, guys have made amazing power numbers; But again, forget the budget.
and like I said
IDK anything about turbos, and IDK your answer.
If it's bottom end you want, just bolt on a set of alloy heads onto a 360, and crank her up close to 200psi, and you'll already have more torque than the chassis can handle. I've never been sorry for the alternative to a turbo, that I chose.
Can you do it with a 318?
Sure, but Not on a budget. It's really hard to get to 11/1 Scr with those tiny cylinders.
It may require Specialty pistons and/or rods , and/or a lot of machining.
Now, if you just use the turbo to pump up the 318 bottom end, that is doable. But you can get torque with a higher stall, much cheaper, and way easier. But now you may need another gear, lol; criminy there goes the budget again.