8-71 Weiand Install - Going Big

We add an 8-71 Weiand blower to our 383

Richard Holdener Oct 9, 2012 0 Comment(s)
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It might be the current economic situation, or possibly because it's an election year or maybe we have all just taken a good look at our waistline, but America seems to minimizing their propensity for super sizing. Small is the new big, with a call to arms to shrink everything from the government right down to the size of a New Yorker's favorite carbonated beverage.

One might question the logic behind imposing limits on a Big Gulp, but who among us wouldn't like to drop a few pounds? In many cases, less really is more, but this particular build up isn't one of those instances. In fact, it's all about more, as in more cubes, more cam and more compression--but we didn't stop there. In keeping with the theme, we even added a large blower. Usually reserved for big-block applications, our big-inch, small-block was topped with nothing less than a dual-quad inducted, 8-71 supercharger from Weiand. Loud and proud, nothing screams "look at me" like an 8-71 sticking out of the hood. The question now was did the massive blower have the bite to back the bark? Was it really worth the effort to "Go Big?"

While it is possible to build small-blocks exceeding 450 inches, doing so requires a great many custom components. Our adventure was more of an off-the-shelf variety, including the eventual displacement of our stroker assembly. Not content with a mere 350 inches, we stepped up to the most common of all small-block stroker dimensions, 383 ci. This was achieved in the usual fashion, by combining a 4.03-inch bore with a 3.75-inch stroke. Knowing boost was also on the list, we opted for a 4340 forged steel stroker crank from Scat matched with a set of its 6.0-inch I-beam rods.

Completing the stroker rotating assembly was a set of forged flat-top pistons from JE and matching rings. Some may question the use of (relatively) high-compression flat-top pistons on a blower motor, but elevated static compression improves off-boost power and fuel economy, to say nothing of maximizing overall power. The trade of is it makes octane rating and tuning more critical. Not wanting to use a production block, we instead chose a new four-bolt race block from Procomp Electronics. Available with either a 4.030- or 4.125-inch bore, we chose the smaller of the two. The beefy block was on hand to withstand the prodigious power offered by the blown stroker.

The camshaft all but determines the personality or more accurately the power curve of the motor. Small cams maximize low-speed power (torque) production, while more aggressive profiles shift power production higher in the rev range. Looking for big power numbers from our 383, we chose our cam accordingly. Choosing a cam from the Crane catalog, we selected one of its powerful solid roller profiles. The Crane cam offered a 0.670/0.625 lift split, a 260/268 duration split and 108-degree lobe separation angle.

We know blower cam guys out there might be wondering where the big intake-to-exhaust split or where the wide LSA are, but believe us, this cam worked well both normally aspirated and supercharged. We've even tested this profile against a so-called blower grind and found the NA cam worked better in both applications. The high-lift, roller cam was ideally suited to the impressive flow rates offered by our cylinder heads. Crane also supplied the roller lifters and 1.5 ratio Gold roller rockers. With our cubes, cam and compression taken care of, it was time to address the induction system. Obviously the stroker would eventually be topped by the massive 8-71 supercharger from Weiand, but we also wanted to break in the motor and make a few pulls in normally aspirated guise to establish a baseline. Looking to optimize the induction system, we combined a set of Super 23 230 heads from Trick Flow Specialties with a single-plane intake from Dart.

In addition to the dual 750 HP carbs for the Weiand blower, Holley also supplied a 950 HP carburetor for our normally aspirated testing. As indicated by the name, the Super 23 230 heads featured 230cc intake ports combined with a 2.08/1.60 valve package and 70cc combustion chambers. The chambers on our heads actually measured just under 72cc, bringing the static compression ratio of our combination to 10.3:1. Since the Super 23 230 heads were capable of supporting 650 hp in normally aspirated trim, we knew they were more than adequate to feed our 383. The heads were secured using Fel Pro gaskets and ARP head studs.

The majority of our stroker was ready, but there were still a few pieces missing. The oiling system came from Moroso, including a billet pump with integrated pick up, pan and windage tray. That billet pump flowed some serious oil, requiring that we step down to the supplied relief spring to decrease oil pressure. Additional components included a complete MSD ignition system including (small cap) billet distributor, wire and ignition amplifier and a set of 1 3/4-inch headers from Hooker. We even ran a 1 inch carb spacer from Wilson Manifolds during testing, which improved the power production by 6-8 hp. After the break-in procedure, the normally aspirated 383 demonstrated its worth by pumping out peak numbers of 571 hp and 497 lb-ft of torque. The Crane roller cam allowed the motor to make peak power at 6,600 rpm and peak torque at 4,900 rpm.

With our baseline testing out of the way, it was time for some boost. Let's be honest, hoisting an 8-71 blower up on the small-block is not for the feint of heart (or body). This is a big chunk of aluminum (and steel), but the results (both visual and dyno) were more than worth the effort. Installation of the blower was basically an intake swap, so off came the single-plane Dart intake and on went the lower (blower) manifold for the Weiand.

When it was properly secured, we hoisted the blower up into place and snugged the blower bolts (Do not over-tighten these!). Feeding the beast was a pair of 750 HP Holley carburetors, both working in unison thanks to the supplied dual-quad linkage. We started things out on the conservative side with a 54-tooth crank pulley and 63-tooth blower pulley, which allowed the blower to spin 14.3 percent slower than the engine. Run at this boost level, the blown 383 produced 728 hp and 625 lb-ft of torque. A 728hp Mouse is nothing to sneeze at, but there was plenty more hiding in the 8-71.

The great thing about superchargers is that more power is just a pulley change away. More blower speed equals more boost, which, in turn, equals more power. Of course all this assumes there is no detonation. With extra blower and crank pulleys at our disposal, we decided to crank up the 8-71. To get things started, we made a small change by swapping out the 63-tooth blower pulley for a smaller 61-tooth version. The blower was still under driven (relative to engine speed) by 11.5 percent, but the resulting increase in blower speed pushed the peak boost level to 8.7 psi and the peak power output to 760 hp and 638 lb-ft of torque.

The previous pulley swap netted an increase in boost of just 1 psi, so we decided to make a major change. The air/fuel was spot on at the elevated boost level, so we felt comfortable making a sizable change in boost. Looking to exceed 800 hp, we installed a larger (57-tooth) crank and smaller (59-tooth) blower pulley. The result was a jump in boost to 11.7 psi and a peak power output of 813 hp. Peak torque was up as well, from 638 lb-ft to 667 lb-ft. Even more impressive was the fact that the power curve was still climbing at our self-imposed shut off point of 6,600 rpm. More boost and more engine speed would certainly yield more power, but how can you argue with an 800hp, 8-71 blown stroker small-block? That, my friends, is Going Big.

Sources

Trick Flow Specialties
Tallmadge, OH 44278
330-630-1555
www.trickflow.com
Crane Cams
Daytona Beach, FL 32117
866-388-5120
http://www.cranecams.com
Dart Machinery
Troy, MI 48084
248-362-1188
www.dartheads.com
JE Pistons
Huntington Beach, CA 92649
714-898-9763
www.jepistons.com
Procomp Electronics
Ontario, CA 91761
909-605-1123
www.procompelectronics.com
Scat Crankshafts
Redondo Beach, CA 90278
310-370-5501
www.scatcrankshafts.com
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