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GM 350 Crate Engine Build VII - The Goodwrench Quest, Part VII

We Bolt On A Weiand 142 Blower And Make 470 HP

Mike Petralia Jun 1, 2000

Step By Step

We keep hammering our Scoggin-Dickey-supplied Goodwrench 350, and it keeps making more power. This time, we stuffed more air into it with a Weiand 142ci Pro-Street blower (PN 6500) and made serious torque and horsepower.

Comp Cams produced a special grind hydraulic-blower cam featuring the same duration figures as our normally aspirated cam, but less lift and a wider lobe separation angle (see Cam Specs). Comp Cams would be happy to grind one for you.

Ed Taylor of Ventura Motorsports installed the new cam straight-up. Most blown street engines don’t need the cam advanced to make tons of bottom-end power, and ours was no exception. Taylor applied a locking compound to the ARP timing-chain bolts and torqued the Comp Cams chain set to 25 lb-ft.

Taylor adjusted the Comp Cams 1.5:1-ratio roller-tip rockers to zero lash plus an additional 1/2 turn.

The Weiand blower intake manifold is designed to fit a Fel-Pro intake gasket (PN 1256). Taylor used silicone on the end rails, which is the best way to seal aluminum intakes.

A blower intake doesn’t look anything like the typical four-barrel manifolds we’re used to, but its primary job is still to direct air and fuel into the cylinder heads. The low-profile Weiand intake means that this blower can fit under older musclecar hoods like the cowl-induction models on Camaros and Chevelles.

This is a critical step that people often ignore. When installing any blower, the hold-down bolts are rarely torqued properly. Weiand’s included instructions that emphasized torquing the blower bolts to 8 to 10 lb-ft (96 to 120 in-lbs) max. This is not a misprint, and any more torque may bind the blower, causing damage and voiding the warranty.

The Holley billet distributor went in after we primed the oiling system using a drill motor and an old distributor shaft. You can see Weiand’s throttle-cable bracket bolted to the back of the blower, which will accept a stock GM cable’s end, although a longer length cable may be required.

If your early Chevy’s water neck exits right or straight out, you’ll need to switch to a neck that exits out the left side (driver side) of the manifold. This may also require radiator modifications to relocate the hose for your new water neck.

Although it’s not visible in this photo, Taylor is using a 3/4-inch box-end wrench on the idler-pulley bolt’s nut to pull the idler arm down. He then slips the blower belt over the idler pulley. Weiand blower kits are available to fit most long and short water pumps and will clear most factory accessory drivebelts.

Installed for the last normally aspirated test, “Goodwrench Quest Part VI,” these TFS aluminum heads worked great with the blower. We had no trouble running as much as 6-psi boost on 92-octane unleaded gas. The efficient combustion-chamber shape and high-flow stainless valves helped our 350 crate engine make over 470 hp.

Lots of horsepower for little money can make you happy, but it’s not always easy to find. In the case of our ever dependable Scoggin-Dickey-supplied Goodwrench Quest 350, we had come upon an impasse. In order to make more power and still retain all of its great street manners, we could either pump the 350 full of nitrous oxide and refill bottles every week or bolt on a blower and see how much power we could pump out of it.

While nitrous may be the current rage at the track, a blower offers several advantages on the street over chemically induced horsepower. For starters, the biggest advantage a blower offers is power on demand. You nail the throttle and the tires light up. That’s it. No bottles to fill, no valves to open, or buttons to push—just hammer it and smile. We wanted that kind of performance for our Mouse, so we contacted the folks at Holley Performance Products and they recommended a Weiand 142ci Pro-Street supercharger. Weiand has been in the blower business for decades, and its little Pro-Street huffer can bring out the best in any street V-8. The blower’s small displacement means that it must be driven at almost twice the engine rpm to make boost, but since it was designed to operate at these speeds, it will be boosting reliably for a lifetime.

Blow To Go

Once again, we asked master Mouse handler Ed Taylor of Ventura Motorsports to strap the Goodwrench 350 onto Ken Duttweiler’s dyno for some power pulls. But before he could do that, we decided to make a few changes. First, to make a blower work really well on the street and produce all the power it’s capable of, it should be combined with a blower-compatible cam. Not all cams work well with blowers, but you can make the most power and always run at peak performance once you’ve installed the proper grind. Typically, blower cams are listed in all the major cam grinders’ catalogs and picking the correct one is as simple as calling the companies on the phone. A blower cam will have a wider lobe separation angle, which decreases the amount of overlap and helps keep the freshly boosted air/fuel charge in the cylinder.

We contacted Comp Cams for a blower cam for the Goodwrench Quest 350, which featured identical duration figures, but slightly less lift than the XE268-H cam we ran in the normally aspirated engine. Comp Cams spread the lobe centers apart by grinding the cam with a 114-degree lobe separation angle, and Taylor installed it straight-up.

After bolting on the TFS aluminum heads for “The Goodwrench Quest, Part VI” article, the small-block calculated a 9:1 compression, which was perfect for a street blower making under 6-psi boost. Considering that the TFS heads are made from aluminum and feature an efficient combustion-chamber shape, we probably could have safely increased compression to 9.5:1, but that would have meant tearing the short-block apart and milling the deck. For the minor increase in power it may have netted us, we determined that was something we didn’t want to do. Although a regular GM HEI would be more than adequate under the low boost conditions you’d normally see on the street, we asked Taylor to install a Holley billet distributor with matching plug wires to ensure that the new boosted air/fuel charge would not have trouble igniting. Everything else in this engine was compatible with the blower, so it was time to visit the dyno.

Pumping Power

Dyno-testing a blown street engine such as this one is a pretty straightforward process. You bolt on a carb that’s big enough to ensure the blower will get all the air it needs to make boost, jet it a little rich to be safe, decrease the total ignition timing a bit to stave off detonation, and then lean on it hard. That’s exactly what Duttweiler did, and the Goodwrench Quest 350 running on 92-octane pump gas reported back sharply with 471 hp. Even more fun was the huge increase in low-end torque we found over its normally aspirated configuration. The dyno began recording data at 2,500 rpm, and the normally aspirated engine made a respectable 357 lb-ft of torque down there. With the blower bolted on, torque at 2,500 rpm jumped to more than 400 lb-ft, almost eclipsing the 410 mark. It gained more than 50 lb-ft of torque at a rpm where most of us are just cruising down the highway. Peak torque also responded well, increasing by 29 lb-ft, making 452 lb-ft at 4,000 rpm. But it’s the low-end that drives you around, and this Mouse’s tremendous low-end is what you’ll feel in your rear!

Interestingly enough, after making several jet changes to the Holley 750-cfm double-pumper carb, Taylor found that the blown Mouse made its best power using the same jets as it did normally aspirated. While it’s unusual for a blown engine not to need more fuel, this could be a case of the carburetor working more efficiently once the blower was installed. It might not have been pulling all the fuel and air it could through its normally aspirated venturis, and the higher venturi velocities created by the blower kept the engine running at peak efficiency. The dyno’s BSFC (brake-specific fuel consumption) numbers hovered around the mid- to upper-4s, showing that our blown Mouse was fairly efficient in converting fuel into horsepower.

Timed To Blow

Ignition timing is most critical in any blown motor—too much and your engine will turn into melted cheesecake; too little and it’ll drive like melted cheesecake. For the first 92-octane pull, Taylor and Duttweiler called upon their years of turbo experience and set the total ignition timing at a conservative 28-degrees advance. The engine responded sluggishly and the exhaust temps were high, both signs that the engine wanted more spark advance.

Taylor bumped the timing to 32 degrees, and the small-block came alive. Peak power was generated using 32 degrees of total advance. It’s important to understand that while this number may have worked well on the dyno, it could be a bit high for the average street car. Your car may load the engine differently than a dyno, and our test day was relatively cool. Higher inlet air temperatures tend to make an engine more prone to detonation, and detonation is the bane of all supercharged engines. Detonation in blown engines can kill a set of pistons before you even hear it knocking, so if you install a blower on your mild street engine, you’d be wise to add forged aluminum pistons to the mix. Adding a shot of 100-octane fuel or octane boost may also be a good idea.

Any way you look at it, installing a blower like the Weiand Pro-Street 142 is money well spent. The power benefits are huge, the installation process is simple, and the rewards are immeasurable. Going blown is certainly the fastest way to get down the highway.

Sources

Chevrolet Performance Parts
Detroit, MI 48232
800-577-6888
www.gmperformanceparts.com
Borla Performance Industries
Oxnard, CA 93033
877-462-6752
www.borla.com
Ventura Motorsports
Ventura, CA 93002
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