Engine Blocks, Parts & Assemblies

Which Engine Blocks Fit Your Engine Family?

Start with your engine family, because bore, deck height, and main journal size change by platform. For small block Chevy builds, Blueprint Engines offers SBC bare blocks with 4.000- or 4.125-inch bores, a 9.025-inch deck, and 350 or 400 mains. Blueprint also builds BBC, SBF, and Gen III/IV LS bare blocks.

Chevrolet Performance offers the 350 Cast Iron Bow Tie Sportsman Competition Block with 400 mains and a 383 bare block. Its lineup also includes the LQ4/LQ9 6.0L Gen III cast-iron block. Dart makes the Pro SHP iron small block Chevy block and the Big M Sportsman iron BBC block with a 4.250-inch bore.

World Products covers both Chevy families with the Motown small block and Merlin IV big block, both cast-iron designs. Ford builders can choose Ford Performance Boss 302 and Boss 351 blocks. There's also a Ford Performance 7.3L gas block with a 107.2mm bore for 2020-2022 Super Duty trucks.

Cast Iron or Aluminum: Which Block Material Fits Your Build?

Cast iron is the durable, cost-conscious pick for most street and bracket builds, while aluminum saves weight for racing. Iron is rigid and holds its shape under heat and load. That's why most blocks on this page, including the Dart, World Products, and Chevrolet Performance options, are cast iron.

Aluminum blocks weigh less and shed heat quickly, which helps front-end weight and handling. They typically cost more than iron, so you'll see them most often in competition engines. The Brodix Custom Aluminum Big Block is the aluminum option for big block Chevy builders.

Your budget, class rules, and vehicle weight goals should drive the choice. Iron fits most street builds, while aluminum makes sense when every pound counts. If you're weighing cost against power, read our guide to a budget vs performance engine build before you buy.

How Do You Choose a Bare Engine Block?

Choose a bare engine block by matching five specs to the parts you plan to run and your power goals. Check each one on the product page before you order.

• Bore size sets displacement and the pistons and piston rings you'll need, such as 4.000 or 4.125 inches on Blueprint SBC blocks.
• Deck height sets how much room you have for stroke, connecting rods, and piston compression height.
• Main journal size must match the crankshafts you're considering, so a 350-main block needs a 350-main crank.
• Cast mains suit most street engines, while billet main caps add strength for high-horsepower builds.
• A 1-piece or 2-piece rear main seal block must match the rear flange design of your crank.

Main journal size also decides which main engine bearings you'll order. Confirm every spec with your machine shop before machining starts.

What's the Difference Between a Bare Block, Short Block, and Long Block?

A bare block is the machined casting with no internal parts, so you pick every component. It's the right start for custom displacement, specific deck heights, or race builds where you control the machining. You'll also handle clearancing, measuring, and assembly yourself or through a shop.

Short block engines arrive with the crank and rotating parts already installed in the block. Long block engines go further and add cylinder heads and top-end parts. Each step up saves assembly time but gives you fewer choices on internal specs.

If you want full control over parts and machining, start with a bare block. If you want a faster path to a running engine, a short block or long block makes more sense. Our article on the difference between a short block and a long block breaks down each option.

What Parts Do You Need to Complete Your Engine Block Build?

A bare block needs a full set of internal parts, each matched to its bore, deck height, and main journal size. Plan these parts before your block goes to the machine shop.

• Crankshafts that match the main journal size and rear main seal style of your block.
• Connecting rods with a length that suits your deck height and stroke.
• Pistons and piston rings sized to your final bore after machining.
• Main and rod bearings that fit your crank journals and clearances.
• Engine block components such as sleeves, freeze plugs, and main cap supports.

Once the bottom end is set, add cylinder heads to finish the long block. Shop each part by spec so it fits your block the first time. Keep your machine shop's final measurements handy when you order bearings and pistons.