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Chevrolet Bowtie Sportsman Engine Block - Stover's Stroker

Cylinder Walls
Robin Stover | Writer
Posted January 1, 2007

Part 1: A Bow Tie Stroker Engine For Mud Bogging And Heavy Hauling

Editor's note: Long overdue, this multi-part story has been on our minds for more than three years now. For those of you who've often wondered when we were going to build a bad-to-the-bone stroker motor from scratch, this is it.

One of the many reasons we like the Bowtie Sportsman block better than other blocks on the market is because it features siamesed cylinder walls, which allows for additional cylinder-bore volume without worrying about running out of material. If you bore out a non-siamesed block, typically it won't cool well. We plan to punch our cylinders to .030 inch over.

We admit it-tech-heavy motor buildups rarely grace these pages. It is because such articles require a significant investment in the form of research, planning, and general legwork. Let's face it-most of us gearheads have to balance our hobbies with our daily routine, family, and budgetary constraints. This lifestyle leaves very little time for component research and engine blueprinting. Then, there is always that ever-present shortage of cash that seems to prevent ordering the necessary parts. Luckily, in this go-around, a few generous industry leaders such as GM Performance Parts, Edelbrock, and Summit Racing were willing to support the cause. With this introduction, we plan to establish a realistic end-all goal for our engine and focus on the best options available to get us there. Following segments will cover all the juicy details about how we built our stroker.

We felt that the above criteria covered 90 percent of what most readers would want from an engine in a real-world daily-driver/tow-rig application that might also be used for mud bogging fun from time to time. Here in California, we have the strictest emissions rules in the nation, so we thought it would make the most sense to build our stroker to California's code and prevent potential hassles later on down the road. We recommend educating yourself about your individual state's smog polices before attempting a buildup like this. We know what the majority of you are saying about this, but believe us, pollution control laws are not going away; if anything, they are only getting stiffer.

Project Criteria
1 California emissions-compliant
2 6,500-rpm redline
3 Reliability for towing
4 91 octane, pump-gas friendly
5 Nitrous-compatible
6 500 rear-wheel horsepower/450 lb-ft of torque (on nitrous)

In the Chevy truck arena, the Bowtie Sportsman block by GM Performance Parts is the cat's meow when it comes to performance per dollar spent. Sure, we could have scored one of those super-lightweight aluminum blocks for this project, and it probably would have made gobs of power and torque, but would its lighter weight really provide any added value in this particular application? We didn't think so. The block you see here is made of iron and runs about $2,200 and is quite capable of handling all of our performance goals when paired with the proper internal components.

Another great feature included with every Bowtie Sportsman block are three center mains, which feature four bolts each, all with 16-degree splayed or angled outers. These main bearing caps are critical to engine longevity. Instead of just two bolts per cap, GM uses four bolts on these center caps to better secure the crank to the block. We like this method because of the added strength it will provide when we hit the nitrous switch. In this photo, you can also see the oil galleys machined into each of the lower mains. This allows oil to flow freely into the main bearings of the crankshaft, a key feature designed to prolong the life of the bearings.

Some of you may remember this '92 Chevy K-1500. We first showcased this vehicle in "The Lowdown on Four-Wheel-Drive Conversions" (June '05), when we demonstrated how to convert a 4x2 Chevy pickup to four-wheel drive. This rig belongs to Off Road Unlimited (ORU) of Burbank, California, and serves both as shop tugboat, and-hopefully soon-mud-bog showboat. In each case, the requirement for usable torque is paramount. Sporting a clean-looking ARB winch bumper and 1-ton axles, equipped with Detroit traction aids and 38-inch Pro Comp Xterrain tires, this rig excels in almost any wheeling scenario. However, its throttle-body-injected 350, with more than 100,000 miles on the clock, is about as useful as a bucket of nails in the fast lane.

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Sources

Summit Racing
Akron, OH
800-230-3030
SummitRacing.com
GM Performance Parts
Detroit, MI 48232
800-577-6888
www.gmperformanceparts.com
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