Performance Questions 225 vs. 360
20#'s of boost? I don't think you need anywhere near 20#'s of boost to get a /6 equal or better power than a stock 360.
This video: [ame="http://www.youtube.com/watch?v=wd6hFGzLJMc"]Turbocharged Slant 6 Chassis Dyno - YouTube[/ame]
Shows Tom Wolfe's (Shaker223) slant six on a chassis dyno making 259 rear wheel horsepower with 21 pounds of boost on an 80,000-mile engine that was stock except for having a Clifford 4bbl intake manifold and a Holley 4bbl carb that had been modified for blow-thru.
That's IT.
Most people use 85-percent as a reference figure to compare chassis dyno output with output at the flywheel when an automatic transmission is used. 259 is 85 percent of 305.
So, the number 20, for boost, to get 300 horsepower with a 225 slant six is pretty accurate IF the test is run on a stock engine with those tiny valves and ports, with a stock cam and a cast iron exhaust manifold with a flange welded to it (no header.)
I imagine that is you put a ported head with big valves (1.75" X 1.5") and optimized the cam for the turbo, and used a proper individual runner header, you could probably make that much power (300 flywheel horsepower) with a lot less boost. Maybe about 15 pounds?
I am just guessing, but those upgrades would have to make a big difference in output, from stock parameters. Add an alky injector and the amount of booost necessary to make that much power would be reduced even further, I'd opine.
I'm using 300hp (flywheel hp) as a nominal figure for a stock 360 based on their 300hp Magnum crate motor, which was a pretty good example of a stock 360, mechanically. Mopar released that figure on an engine that was dyno'd with a 750 Holley and headers.
So, yes, I think you could probably equal that 300hp V8 performance with a semi-"built" slant six that had a ported head with big valves, a 4bbl, an alky injector and a turbo cam, using only about 15 pounds of boost.
That is all strictly conjecture on my part; your mileage may vary! :cheers:
I want to reiterate what I said about rear end selection for a slant six/turbo-equipped car vs. a V8-swapped car:
The rear axle ratios in the two quickest A Body turbo slant six cars that I have seen evidence of, are 2.76:1 for the strip AND for the street. The turbo motors are weird, in that the car slows down with normally-"steep" rear gears, such as the 4.56:1 units often found in small-block cars. The turbo motor seems to make more power (not unlike a "fuel" motor) when it is "held back" and not allowed to increase rpm quickly. The significance if this is, the turbo motors also can use the same ratio for highway driving AND drag strip action. The small block "built" motor wouldn't much like a 2.76:1 rear end on the drag strip, nor would it perform up to its potential, with a 4.56:1 on the highway. So, if you build a small block and it does double duty, you really need two sets of gears; one for the drag strip and one of the highway. No problem; you can change third members in a couple of hours (or, less.) But, they don't give away 8.75" A-Body housings these days, and neither is it cheap to buy and maintain two sets of third members, with different ratios; one for racing, blah, blah, blah...
The turbo slant six car can easily make do with a "one-ratio-fits-all" rear end. A late model, A Body 8.25" rear end from a junk yard will be lots cheaper (or, one out of an Aspen/Volare car) and will come with highway (and drag strip) gears already in it.... and is plenty strong for this application.
So, in my opinion, the rear end situation is not at all "a wash" because of the foregoing...
one more reason to keep granny's engine on its mounts!!! LOL!
