Project Black Betty
I enjoy the /6 builds. A turboed slant may be my next project. I've got a 69 225/904 and a Duster shell sitting in the weeds.
You've got the raw materials, but depending on how fast you want this car to be, you might consider some alternatives on the base engine's hard parts.
The choices are defined by quarter-mile e.t's, which are defined by various boost levels you might want to run.
At the bottom of the heap would be a fourteen-second car that should be a good race for a stock, 340 Duster and would use the stock reciprocating assembly (stock pistons, rods and crank) and a cylinder head that had been treated to bigger valves (1.74"/1.5") but, no actual porting beyond some minimal pocket-porting in the area underneath the valve head. Cheap...
This base engine would use a turbocharger sized like the one on a Buick Grand National turbo motor's, and if you could find an actual Buick turbo, that would be ideal, because those factory GM Buick turbos (in 1987 and 1988) had a built-in wastegate, so that's one item you wouldn't have to buy or plumb...
A Pishta-design J-pipe turbo-mount that attaches (bolts on) to a stock slant six exhaust manifold would work nicely on this engine. No welding!
The intake would be a Super Six, 2bbl intake manifold mounting a Holley 500cfm 2-bbl carb that had been treated to a set of blow-thru mods to ensure the proper mixture under boost.
A stock distributor could be used, if you limited the total mechanical spark advance to 18 degrees. The stock, vacuum advance unit could add enough spark advance to ensure cool running and reasonable fuel economy.
The stock cam and rocker arm assembly would work nicely in this motor, I think.
That motor, if equipped with a Snowperformance Stage I "Boost Cooler" water/alcohol injector (about $300.00) would provide about 280 horsepower, maybe 300, on pump gas. Not a bad bang for the buck.
A "Stage Two" version of that engine would be more expensive, but would provide a lot more performance on the drag strip.
That engine would include some detail changes that would ensure reliability and increased grunt, putting it on par with some modified V8's in acceleration.
It would have forged pistons ($$$) and 198-length rods ($$$) on an early model (forged crank... cheap), a 4bbl intake manifold (usually available used, for around $150.00) and a 600fm Holley 4-bbl , modified for draw-thru ($$$) and that same stock ignition system, but with a MSD 6-AL digital module for a healthy spark. Again, 18-degrees of advance, maximum under all conditions.
At this point, a fully-ported head would be advised, with the same 1.74"/1.5" valves.
A flat-tappet cam with .480"-lift and 210-degrees duration, ground with about 115-degrees of lobe separation, would fit this engine combination well.
A torque converter with about 3,000 rpm stall speed would make possible some pretty strong launches, so you didn't have to play "catch-up" at the strip...
This car, with the right tire. would probably be capable of mid-11 second e.t.s, but would be somewhat more expnsive to build than the other motor.
Neither motor should need an intercooler (especially, if you use a water/alcohol injector.) That could change if you ramp the boost on this second motor up to levels above 20psi.
Horsepower on this second motor would depend on boost, of course, but 15 pounds should give you a low 12-second car and it should run on 93-octane pump gas and last indefinitely. Probably 350 flywheel HP with this setup and 15 pounds of boost, and I think that estimate is conservative.
I cannot estimate the HP improvement of a custom slant6 turbo header over the Pishta J-pipe setup.... but, it would probably be worth something... sorry... but, it wouln't be necessary or, even, desirable on the Base "build."
The bonus of a setup like this "base" one, is, you can run pump gas, have a smooth idle, and it will be VERY happy with a rear axle ratio in the high twos (2.73, 2.76, 2.93:1, etc.) which is easily attainable by installing the (cheap-to-buy) 8.25" rear end from a late-model A-Body/automatic, such as a '76 Duster V8 or an Aspen/Volare. That way you have a "one ratio fits all," bolt-in, final drive.... no need for an expensive 8.75" drop-out rear for swapping those hiway gears for a 4.56:1 for the strip.... the turbo slant6 likes the low numbers, even at the strip.
The base engine could provide a lot of fun for very little (comparably) money, and would be a great place to start. A low-14-second slant six is a great way to go, I think!
Good luck, with whatever you choose...:cheers:
