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A 6-71 blower can do more than just make you stand out in a crowd

Back To Our Roots

Richard Holdener Sep 27, 2018
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When someone offers up a crate engine, then wants you to run power-adders on it, what do you do? For us, the answer was easy, we grabbed some nitrous and a handfull of superchargers and hit the dyno. Basically, we ran the living stink out of it. The crate engine in question was the power-adder ready 383 Stroker Crate Engine (BP38317CT1) offered by BluePrint Engines (BPE). Built with power-adders in mind, the 383 stroker featured all the important components, including BluePrint’s own four-bolt block, forged internals, and a power-adder friendly static compression ratio of 8.9:1. The fortified internals included a 3.75-inch stroker crank, 5.70-inch I-beam connecting rods, and forged aluminum pistons. Finishing up the stroker long block was a healthy cam profile and free-flowing aluminum heads. Rated by BPE at 445 hp, our crate combo pumped out right at 446 hp and 466 lb-ft of torque using an Edelbrock Performer RPM Air-Gap intake manifold and Holley 650-cfm carb. Obviously, the BPE guys did their homework on this crate engine, but what we wanted to see was how well the combo stood up to the additional power from nitrous and boost.

In our early testing with the 383, we subjected it to both juice and boost, with a Zex nitrous kit being first on the list. Run with 75hp jetting, the Zex-injected 383 thumped out 516 hp and 546 lb-ft of torque. After stepping up to 100hp jetting, the power output jumped to 572 hp and 607 lb-ft of torque. Obviously, the power-adder crate engine thrived on the juice, but we followed that up with some boost from a TorqStorm supercharger. Run with the centrifugal supercharger, the boosted small-block produced 635 hp and 596 lb-ft of torque at a peak boost reading of 9.6 psi. Once again, the BPE 383 shrugged off the boost like a boss, and asked if there was any more? As it turned out, we had more, and more in this case came in the form of a Weiand 6-71 supercharger. Used for decades, but made famous by movies like The Hollywood Knights, Road Warrior, and, most recently, the Fast & the Furious franchise, big roots blowers provide more than just boost. The aural and visual statements offered by a big blower are every bit as important as the actual output.

019 Blueprint  Stroker  6 71  Boost  Weiand 2/19

Given the rich history, it seemed only appropriate that we try one of these beauties on our 383. A quick call to Weiand netted one of their polished 6-71 kits, replete with provisions for dual quads! After all, the only thing better than a big blower is one topped with a pair of four-barrel carburetors. The last thing you want to do is restrict the supercharger with insufficient air or fuel. The Weiand supercharger kit included everything we needed to install the blower out our 383 small-block. To the kit we added a pair of Holley 750 blower-specific carburetors. Among other things, the blower carbs featured boost-referenced power valves that allowed us to dial in the air/fuel mixture under cruise and WOT. After all, who wants to run down the road in their 6-71 blubbering from an excessively rich mixture? We also requested a variety of different supercharger/crank pulleys. The Weiand boys shipped us out pulleys ranging from 34 teeth up to 38 teeth. This provided drive ratios ranging from 11 percent under (slower than engine speed) to nearly 12 percent over (faster than engine speed). For our testing, we only ran the blower a maximum of 2.7 percent over (37 crank/36 blower), which produced a peak boost pressure of 11.4 psi. And, we all know that boost equals power!

002 Blueprint  Stroker  6 71  Boost  Weiand 3/19

The power-adder-ready 383 crate engine from BluePrint Engines (BPE) featured a host of forged internals and boost-friendly 8.9:1 compression in a U.S.-made four-bolt block. The stroker assembly also included a healthy cam profile and free-flowing aluminum heads. The only thing missing was an induction system and a proper power-adder.

003 Blueprint  Stroker  6 71  Boost  Weiand 4/19

To prep for our naturally aspirated baseline, we added an Edelbrock Performer RPM Air-Gap intake.

004 Blueprint  Stroker  6 71  Boost  Weiand 5/19

Before adding boost, we ran the 383 once again in naturally aspirated trim with a Holley XP carb and MSD distributor. So equipped, the BPE 383 produced 446 hp and 466 lb-ft of torque.

005 Blueprint  Stroker  6 71  Boost  Weiand 6/19

Off came the Edelbrock intake to make room for the dedicated Weiand blower manifold.

006 Blueprint  Stroker  6 71  Boost  Weiand 7/19

We installed the lower intake supplied with the Weiand 6-71 supercharger kit. Note the position and orientation of the thermostat housing (our Wilson unit was adjustable).

007 Blueprint  Stroker  6 71  Boost  Weiand 8/19

Before setting the 6-71 supercharger in place, we made sure to install the spring-loaded blow-off valve. Make sure to adjust the spring tension according to the supplied instructions.

008 Blueprint  Stroker  6 71  Boost  Weiand 9/19

To monitor the inlet air temperatures (IATs) below the supercharger, we installed this temperature probe. This data would be extremely valuable later on when we planned on testing some E85, but that’s another story for another day.

009 Blueprint  Stroker  6 71  Boost  Weiand 10/19

Before setting the (heavy) 6-71 supercharger in place on the intake manifold, make sure to remove this warning label (and DON’T over-torque the blower bolts!).

010 Blueprint  Stroker  6 71  Boost  Weiand 11/19

With the warning label removed, we installed the polished 6-71 supercharger in place on the intake manifold. Note the aluminum blower bolts used to secure the supercharger.

011 Blueprint  Stroker  6 71  Boost  Weiand 12/19

We then installed the dual-quad adapter on top of the supercharger. This allowed us to run a pair of Holley blower carbs.

012 Blueprint  Stroker  6 71  Boost  Weiand 13/19

We requested a number of different supercharger pulleys to allow us to adjust the boost supplied by the supercharger. Identified by tooth count, we chose pulleys ranging from 34 to 38 teeth, and started with the largest pulley on the supercharger.

013 Blueprint  Stroker  6 71  Boost  Weiand 14/19

By running the smallest pulley on the crank, this combination produced the lowest possible boost level on our small-block. It’s always better to start low and increase after everything is right.

014 Blueprint  Stroker  6 71  Boost  Weiand 15/19

The supercharger required a small-cap MSD distributor. We ran this Pro-Billet version with an MSD 6AL ignition amplifier.

015 Blueprint  Stroker  6 71  Boost  Weiand 16/19

The kit included both the blower belt and tensioner assembly. Make sure not to over-tension the blower belt. With everything tightened up it was almost time to fire up the dyno.

016 Blueprint  Stroker  6 71  Boost  Weiand 17/19

To feed the beast, we enlisted the aid of a pair of Holley 750 blower carbs. Designed specifically for boosted applications, they featured dual 50cc accelerator pumps and boosted-referenced power valves. Ours worked perfectly right out of the box!

017 Graph 1 18/19

Having run the BPE 383 a number of times in the past, we knew it was capable of handling almost anything we could throw at it. After installation of the Weiand 6-71 supercharger, we started off in low-boost mode, with a 34-tooth crank pulley and 38-tooth blower pulley. Driven 11 percent under, the 6-71 produced a boost curve that began at 4.2 psi at 3,300 rpm and rose to 8.3 psi at 6,400 rpm. This pulley combination produced peak power numbers of 602 hp at 6,400 rpm and 551 lb-ft of torque at 4,700 rpm.

018 Graph 2 19/19

Since we requested a number of different crank/blower pulley combinations, we decided to put them to good use. After producing 602 hp and 551 lb-ft of torque with the 34-tooth crank pulley and 38-tooth blower pulley, we made a change. After installation of the 37-tooth crank pulley and 36-tooth blower pulley, both the peak boost and power output increased substantially. With a peak boost of 11.4 psi, the supercharged 383 produced 643 hp and 589 lb-ft of torque. Mad Max would be proud! For us, we’d opt for the 602hp version running at 8.3 psi. But just wait till you see what happened when we added E85 to the mix. All we can say is, no wonder the corn so popular among racers!

Sources

Westech Performance
Mira Loma, CA 91752
951-685-4767
www.westechperformance.com
Blueprint Engines
Kearney, NE
800-483-4263
http://www.blueprintengines.com
Holley
Bowling Green, KY 42101
270-782-2900
www.Holley.com
Edelbrock
Torrance, CA 90503
310-781-2222
www.edelbrock.com
MSD Ignition
888-258-3835
www.msdignition.com

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