Big Block Chevy Engine - Battle Of The Boost

Mini Blower Vs. 8-71 On A Basic Rat

David Freiburger Dec 17, 2006 0 Comment(s)

Want big grunt? Go Roots, man. No other single bolt-on will give you a bigger kick in the torque curve, at least not without having to refill a bottle all the time. A Roots supercharger is the simplest way to get boost, since it doesn't require EFI, trick carbs, complicated fuel systems, or any air-tube plumbing. Not that centrifugal blowers aren't fantastic, but they usually don't deliver the same snap-to-life start-up and right-at-the-toe low-end bark you get with a Roots. The only problem is you may get some flak from today's hipsters who'll guffaw at the '80s-throwback hole in your hood and want to talk adiabatic efficiency instead of good old-fashioned tire frying.

Of course, the solution for the hole in the hood is a mini blower, which will fit under most small cowls. In this story we compare the price and performance of a Weiand 177 mini blower to a traditional and far more imposing Weiand 8-71 fullsize supercharger. Unlike the old days, when magazines made it seem like you needed a full-on race motor to support blown power, we'll run these on a very pedestrian big-block.

The Victim
Look at the parts lists and you'll learn every single component that went into this Rat motor. Make sure you check this out: It's got a Scat cast crank, Scat's most basic connecting rods, and a tiny Crane Saturday Night Special flat-tappet cam (PN 134551) with 236/246-degrees of duration at 0.050, 0.553/0.571 lift with 1.7:1 rockers, and an LDA of 110. It couldn't be much more basic. There was a time when you'd never consider using a cast crank with supercharged power, and while it's still not the first choice, the new Scat Series 9000 cranks seem to be stronger than factory castings. Since we're not going to try to overpower it or snap off the snout with huge boost, it works. We wouldn't recommend it with a transbrake, though, even at the power levels seen here.

The crank itself is just $299 and the rods are $320, which is almost cheaper than reconditioning the stock parts and adding good rod bolts. Since that's true, and because you've got to buy new pistons for an overbore anyway, there's no reason not to stroke a big-block these days. The 4.250-inch stroker crank is the same price as the stock 4.00-inch stroke, and combined with a 0.030-inch overbore our Mark V block from the junkyard now delivers 489 ci. With affordable SRP forged flat-top pistons (because we still can't bring ourselves to recommend hypereutectics with a blower) and 110cc chambers in Holley oval-port heads, the compression is 8.95:1.

It's practically a tow-truck engine. In naturally aspirated trim, using a Professional Products high-rise, dual-plane intake, and an 800-cfm Holley, it made 549 hp at 5,300 rpm and 597 lb-ft at 4,000 rpm. Not earth-shattering, but pretty good for junk that will run on 87-octane. Now let's wake it up.




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