Twin Turbo 1971 Scamp Project
I agree. I love the slants so for me there really isn't too much of an arm twist. But Tim's Dart was beyond insane and a turbo small block might not cost much more! ;) Plus if you got an EFI Magnum starter engine you'd have PFI already. ;) All of my turbo stuff generally ends up with EFI. Nothing wrong with a blow through carb but I like laptop tweaks after the fact.
My problem is, I don't know much about the factory fuel injection that came on the factory 360 Magnums. I have a 318 Magnum in my '93 Dakota and I have never read a good word about the "beer barrel" intake manifold that rests on top of that particular configuration of injected Magnum. Everybody bad-mouths its design, and contends that it breathes very poorly. I have to assume that later versions that came om 360s were better, but, how much better? Would you choose to use that manifold/injection setup for your 350 (flywheel) horsepower build? Or, is it a design that would make it difficult to actually make 350 (flywheel) horsepower, in which case, you'd probably opt for something like an Air Gap manifold with some sort of throttle-body injector on top?
Like I said, I have scant knowledge about cost-effective fuel injection systems for these 360 Magnums.
Cost considerations are going to play a big part in this comparison, because a 350 (flywheel-horsepower) turbocharged slant six is not going to cost very much at all to build. I am thinking a stock reciprocating assembly, stock cam with some homemade 1.6:1 rocker arms (like mine,) a used Super-six 2bbl intake manifold, a Holley 500 two-barrel on top, a Pishta-design (J-Pipe) turbo mount, a Lean-Burn distributor with a locked plate, and a bone-stock head. I would definitely use an alcohol injector, but the jury is still out on what type, because a Snowperformance Boost Cooler
base model is $300.00 and I think we can probably get it done with some sort of home-brewed system for about half that.
Stock converter, and a 2.76:1, 8.25" rear axle out of an Aspen/Volare.
I am opining that ten pounds of boost will give us 300 rear wheel horsepower. That would equate to about 350 flywheel horsepower, I think.
That's my best guess. But, that's all it is... a guess; what do I know??? LOL!
I realize that it will only take a cam and a set of headers, probably, (and, maybe a small increase in the compression ratio,) to get that much power out of a 360 Magnum, but there are other considerations besides just engine modifications to consider if this vehicle is going to be a useful, driveable, vehicle.
Considering cost, initially, the slant six is a throw-away engine and can be gotten for little or nothing. A 360 Magnum with a working fuel injection system is likely not going to be a "freebie." So, the disparity of initial cost must be factored into the final cost/equation.
In order to make decent mid-range torque, for decent driveability, the 9:1 compression of that Magnum engine would probably need to be increased by a little, maybe up to 10: when the necessary longer-duration cam is added, which would probably be required to get 350 flywheel hp. Milling (for increased compression) costs money, particularly in the case of a V8. which has to have the angled surfaces of the intake manifold and the bottom of the intake manifold milled, anytime the heads are milled. The slant six will require NO milling of anything, since the turbo will work well with the stock compression ratio.
A stock torque converter will work well with the /6's stock cam; the V8 MAY require a higher-stall converter, depending on the cam profile. Maybe not...
The Pishta-design turbo mount for the slant 6 can be built for probably less than $75.00. The headers for the 360 will cost more... just how much more will depend on the source. The cost of the turbo and wastegate is a matter for conjecture, as this is being written. A properly-sized turbo might be difficult to locate for this application, dunno...
No intercooler should be needed.
Turbo slant sixes have a strange behavioral facet to their performance-personality, in that they seem to like to be heavily loaded to make good power. Test have demostrated that the best quarter-mile acceleration times come with final drive ratios in the high "twos." That means that a slant six turbo car only needs one ratio to perform well at the drag strip AND on the highway.
Not so, the V8 car. That 4.56 gear that makes for great e.t.'s at the strip, will prove to be less than ideal on the highway at 70 mph. Gas mileaage and engine-wear considerations will dictate that you have two sets of gears for that 12-second puppy; a 2.76:1 Highway gear and a 4.10 or 4.56 for the streip, if you want to do much racing. That 2.76 gear will sslow you down about 3 car-lengths... or, more.
That all means that you're going to need a drop-out center-section for the frequent gear changes you'll likely be required to make. They don't give away A-Body 8.75" housings any more... plus, you'll have the added expense of setting up TWO sets of gears... not cheap.
The slant six's 8.25" will already have the gear you need, in all likelihood...
All of that needs to be considered as part and parcel of the V8 vs. /6 swap when comparing the
real cost of a V8-powered car or a turbo'd slant six car.
Lots to consider beyond the basic cost of the engine...
Here is Pishta's setup