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

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.