Page 117 of 2009 Performance Parts by GM Parts Direct

chevy big-block v-8 the new big block the classic chevy big-block production engine was introduced in 1965 in the late 1980s a new version arrived designed for marine and fuel-injected applications the early-style engines are known as mark iv big-blocks while the later style is referred to as the gen v and gen vi big-block you can tell them at a glance by checking for a mechanical fuel pump mounting pad if it has one it s a mark iv if there s no fuel pump pad it s a gen v block despite the fuel pump mounting pad difference in their castings the cylinder blocks of the mark iv and gen v are based on the same design architecture there are several other differences particularly in the water jackets near the deck surfaces that make some mark iv and gen v parts incompatible including crucial components such as the cylinder head gaskets gm recently revised the basic big-block architecture to commonize the mark iv and gen v creating an all-new cylinder block casting that commonizes the features of both generations it also incorporates significant updates and strength-enhancing features that make the big-block a stronger engine foundation with provisions to support 21st-century performance although the basic big-block architecture is revised gm performance parts continues to offer two versions each differentiated by performance and displacement capability the bowtie block continues to be the block of maximum performance gm performance parts crate engines use the revised big-block design chevy big-block quick reference chart production-based cast-iron blocks part number 19170538 19170540 casting number deck height 9.800 9.800 f pump boss yes yes cyl wall open siamese bore range 4.250 ­4.310 4.470 ­4.500 main bolt 4 4 main blt degree straight straight cap material cast-iron cast-iron crank oiling jnl dia 2.75 2.75 wet wet seal type 1pc 1pc max weight stroke lbs 4.25 4.25 247 269 max hp 700 700 usage street mod page number 232 232 chevy big-block v-8 bowtie cast-iron big-blocks part number 19212191 19212192 19212193 19212194 19212195 19212196 19212197 cast number 24502504b 24502504b deck height 9.800 9.800 f pump boss yes yes yes yes yes yes yes cyl wall siamese siamese siamese siamese siamese bore range 4.494 ­4.600 4.494 ­4.600 4.494 ­ 4.600 4.494 ­4.600 4.560 ­4.600 main bolt 4 4 4 4 4 4 4 main bolt degree 16° 16° 16° 16° 16° 16° 16° cap material nodular nodular nodular nodular nodular 8620steel 8620steel crank oiling jnl size 2.75 2.75 2.75 2.75 2.75 2.75 2.75 wet wet wet wet wet wet wet seal type 2pc 1pc 1pc 2pc 1pc 2pc 2pc max weight stroke lbs 4.50 4.50 4.50 4.50 4.50 4.50 4.50 258 258 263 263 263 281 296 max hp 800 800 800 800 800 1200 1200 usage sport sport sport sport sport pro pro page number 233 233 234 234 234 236 236 24502506b 10.200 24502506b 10.200 24502506b 10.200 24502504b 9.800 24502506b 10.200 siamese 4.240 ­ 4.600 siamese 4.240 ­ 4.600 here s how we updated the biggest and baddest performance engine platform of the past 45 years · water jackets were revised near the deck surfaces so that mark iv or gen v head gaskets can be used interchangeably · oil pressure feed holes were added to the oil filter boss and front bulkhead to support oil feeds for superchargers turbochargers etc · the oil hole next to the camshaft bore at the front of the block was repositioned enabling safe machining of the cam bore to accept a 50mm roller camshaft bearing · a mechanical fuel pump mounting pad became standard similar to the mark iv · a boss was added next to the distributor hole in the valley to support hardware for digital ignition equipment · revised front bulkhead was made thicker and stronger with marked provisions for 10-bolt timing cover non-bowtie blocks are delivered with drilled and tapped holes for six-bolt covers remaining holes must be drilled and tapped at the prescribed positions · non-bowtie blocks were machined for four-bolt parallel main caps bowtie blocks are machined for four-bolt splayed caps · revised rear-of-block allowed for the machining of one or two-piece main seals similar to gen v design · the front clutch boss was added for older muscle car applications · 454 blocks created a slightly beefier main web than previous blocks · all blocks were made with the standard production roller camshaft and lifter machining · 502 and bowtie blocks shared the same main web which is strengthened considerably from the mark iv and the first-generation gen v bowtie block · bowtie blocks were given a distinctive water jacket design to allow up to 4.600 bores these blocks can be identified by a b suffix behind the casting number additionally two new core plugs were added to the rear bulkhead they enhance the manufacturing process at the foundry and help improve overall quality also new bowtie logo and other identifying marks are added to the bowtie block distinguishing it from previous generations aluminum zl1 block part number 12370850 88958696 cast number 3946053 88958695 deck height 9.800 9.800 f pump boss yes yes cyl wall siamese siamese bore range 4.240 ­4.300 4.250 ­4.300 main bolt 4 4 main bolt degree 16° 16° cap material 8620steel 8620steel crank oiling jnl size 2.75 2.75 wet wet seal type 2pc 1pc max weight stroke lbs 4.38 4.38 110 110 max hp 650 650 usage pro pro page number 235 235 drce blocks part number 24502572 25534406 cast number 1a626 cg deck height 9.525 9.25 ­9.0 f pump boss no no cyl wall siamese siamese bore range 4.500 ­4.700 4.590 ­4.700 main bolt 4 4 main bolt degree 16° 22° cap material 8620steel 4140steel crank oiling jnl size 2.75 2.50 dry dry seal type 2pc 2pc max weight stroke lbs 4.60 4.60 255 n/a max hp 1400 1400 usage pro pro page number 237 237 builders tip valve-to-piston clearance considerations a custom engine combination should always raise the concern of valve-to-piston clearance and while camshaft lift is commonly thought of as the primary culprit of valve/piston interference the overlap period ­ when the piston nears top-dead center and the intake valve is starting to open and the exhaust valve is closing ­ brings the valves and piston closest together so don t assume the gross lift specs are all you have to worry about duration and lobe separation are equally important making a careful clearance inspection all the more important 230 buy online at www.gmperformanceparts.com buy online at www.gmperformanceparts.com 231

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