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Chevy small-block v-8<br />
GM Performance Parts Bowtie<br />
Sportsman Block<br />
Step up to serious street/strip performance when you choose a<br />
GM Performance Parts Sportsman Block. These iron blocks provide<br />
a rock-solid foundation for any application in the 350-500-horsepower<br />
range, be <strong>it</strong> drag strip, circle track or high-performance street<br />
machine. These highly versatile blocks are available in a variety of<br />
finish options that enable maximum flexibil<strong>it</strong>y for building a wide<br />
variety of engine <strong>com</strong>bos. Most of the blocks have siamesed<br />
cylinder walls 1 and 4-bolt main caps 2 that are secured w<strong>it</strong>h Grade<br />
8 bolts. GM Performance Parts Bowtie Sportsman Blocks have<br />
9.025-inch deck heights.<br />
NOTE: Bowtie blocks are called out by main journal sizes (i.e.,<br />
283, 350 or 400) and then by bore size (i.e., 283, 305, 350 or<br />
400) if the bore is not standard to the main size. Example: P/N<br />
24502650—“283 Main-350 Bore size”—has standard 283 main<br />
journal sizes; however the bore is standard 350 size.<br />
Bowtie Sportsman Block Technical Notes:<br />
• Standard 9.025-inch deck height<br />
• Nominal cylinder wall thickness is 0.340-inch<br />
• Minimum cylinder wall bore thickness on 4.155-inch bore is<br />
0.225 inches (excluding P/N 10051181, 10051183, and 10185047)<br />
• Extra thick deck surfaces have blind-tapped bolt holes for<br />
improved head gasket sealing<br />
• Prior<strong>it</strong>y main oiling system<br />
• Main bearing bulkheads are 0.900-inch thick and use Grade 8<br />
bolts<br />
• All five cam bearing locations require 2.00-inch O.D. (1.867-inch<br />
I.D.) bearings P/N 12370843 (except block P/N 10051183)<br />
• Tall lifter bore blocks may require clearancing the top of the lifter<br />
bores for some roller lifters<br />
• Lifter valley oil scavenging boss below bell housing flange is<br />
present, but not drilled and tapped<br />
• Oil dipstick holes are not drilled<br />
• Timing system clearance must be checked<br />
• Seal adapter P/N 10051118 required to use two-piece rear main<br />
crankshafts in one-piece rear main blocks<br />
A<br />
Sportsman Block (front)<br />
350 Bowtie Sportsman Block, 2-Piece Rear Main Seal<br />
B<br />
B. 12480047<br />
350 Bowtie Sportsman Block, 2-Piece<br />
Rear Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center three mains<br />
• 3.980" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
12480175<br />
350 Main, 400 Bore Size Bowtie Sportsman Block,<br />
1-Piece Rear Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center three mains<br />
• 4.117" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
• Comes w<strong>it</strong>h rear seal adapter<br />
12480157<br />
350 Main, 400 Bore Size Bowtie Sportsman Block,<br />
2-Piece Rear Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center three mains<br />
• 4.117" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
Chevy small-block v-8<br />
4-Bolt 400 Main Blocks<br />
12480049<br />
400 Main, 350 Bore Size Bowtie Sportsman Block,<br />
2-Piece Rear Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center three mains<br />
• 3.980" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
See the chart on page 134 for <strong>com</strong>plete specifications.<br />
4-Bolt 350 Main Blocks<br />
A. 10185047<br />
350 Bowtie Sportsman Block, 1-Piece Rear<br />
Main Seal<br />
• Cast-iron maximum effort block<br />
• 4-bolt “straight” nodular mains<br />
• 3.980" rough bore<br />
• 4.090" max bore (siamese cylinder bores)<br />
• Replaces older 4-bolt, 2-piece rear main seal block<br />
P/N 366287<br />
• Rear main seal adapter required!<br />
A<br />
Sportsman Block (rear, for use w<strong>it</strong>h 1-piece seal adapter)<br />
350 Bowtie Sportsman Block, 2-Piece Rear Main Seal<br />
B<br />
12480159<br />
400 Bowtie Sportsman Block, 2-Piece Rear Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center three mains<br />
• 4.117" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
12480174<br />
350 Bowtie Sportsman Block, 1-Piece Rear<br />
Main Seal<br />
• CNC-machined cast-iron <strong>com</strong>pet<strong>it</strong>ion block<br />
• +/-0.001" machining tolerances<br />
• 4-bolt nodular mains, splayed caps on center 3 mains<br />
• 3.980" finished bore<br />
• 4.155" max bore (siamese cylinder bores)<br />
• Extra smooth gasket surfaces for better seal<br />
• Tall lifter bores<br />
• Comes w<strong>it</strong>h rear seal adapter<br />
1<br />
Siamesed cylinder walls have thicker cylinder wall material w<strong>it</strong>h no water<br />
between the bores. This allows for a bigger bore; a bigger bore allows for more<br />
cubic inches and more power!<br />
Builder's Tip<br />
Cylinder Honing w<strong>it</strong>h a Torque Plate<br />
Most GM Performance Parts cylinder blocks require final honing prior<br />
to building the engine. So when you take your new block to your local<br />
machine shop for honing, you should consider having this procedure<br />
performed w<strong>it</strong>h torque plates installed on the deck surfaces. These tools<br />
approximate the load and minute distortion on the block that occurs when<br />
the cylinder heads are installed. By having the cylinders honed w<strong>it</strong>h a<br />
torque plate, you’ll ensure better cylinder pressure and reduce the likelihood<br />
of leaks. And, if you plan to supercharge, turbocharge or n<strong>it</strong>rous-feed<br />
your Small-Block, torque-plate honing is a must!<br />
2<br />
4-bolt mains have more material and more fasteners holding the crank in the<br />
block (4-bolts per main instead of just 2). 4-bolt mains help maintain the integr<strong>it</strong>y<br />
of the block when you drop the hammer!<br />
2-Piece Rear Main Seal<br />
4-Bolt Splayed Main Caps<br />
136 Buy online at www.gmperformanceparts.<strong>com</strong><br />
Available for purchase online at<br />
gmperformanceparts.<strong>com</strong><br />
137
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