Engine Blocks & Block Components

How Do You Choose the Right Engine Block Parts?

Start with your block's make, displacement, and the job at hand. Most parts here are application-specific, so a plug sized for a 1947-50 Chevrolet won't seal a Ford 4.0L. This category breaks down into five groups:

• Freeze plugs and expansion plugs that seal casting holes and coolant passages
• Cylinder sleeves that restore a damaged or worn-out bore
• Main caps and main cap girdles that hold the crankshaft in place
• Oil restrictors and relief valve parts that control oil flow
• Bellhousing dowel pins and block hardware that keep parts aligned

If your block is cracked or too far gone to repair, compare bare castings in engine blocks first. For heads, rotating assemblies, and other internal parts, browse the full Engines & Components category.

Which Freeze Plugs and Expansion Plugs Fit Your Block?

The right freeze plug matches your block's hole diameter and the way you can install it. Freeze plugs, also called core plugs or engine block plugs, seal the holes left in the water jacket during casting. You'll typically choose from three types:

• Steel plugs for direct replacement of factory-style press-in plugs
• Brass plugs for added corrosion resistance in the cooling system
• Rubber expansion plugs that tighten in place when you can't drive in a press-fit plug

Dorman Products rubber expansion plugs include a universal 2-1/4" to 2-3/8" size and a fit for 1947-50 Chevrolet engines. For late-model engines, Melling offers an expansion plug kit for Chrysler, Dodge, Jeep, and Ram 5.7L, 6.1L, and 6.4L engines. Melling also makes a jackshaft plug for the Ford 4.0L. You'll also find expansion plugs for 1987-2006 Jeep 2.5L, 4.0L, and 4.2L engines.

Before you drive in a new plug, coat its sealing edge with a product from block filler & sealers.

When Should You Use Cylinder Sleeves?

Use cylinder sleeves when a bore is cracked, scored, or worn past its overbore limit. A sleeve lets you repair the damaged cylinder without replacing the block.

Engine block sleeves come in two designs. Dry sleeves press into the block and never touch coolant. Wet sleeves form part of the water jacket and contact coolant directly.

Dart block sleeves are available for big-block Chevy and small-block Chevy builds. Melling cylinder sleeves come in several bore sizes, such as the CSL729 with a 2.9720" bore, 5-1/8" length, and 1/8" wall. Other Melling options include 3.1610", 3.3860", 3.4840", and 3.6610" bores.

Plan on machine-shop work for any sleeve job. The shop bores the block to accept the sleeve, then bores and hones the sleeve to your finished size. Confirm the sleeve's bore, length, and wall thickness against your block before you order.

How Do Main Caps and Girdles Strengthen the Bottom End?

Main caps clamp the crankshaft's main bearings to the block, so stronger caps add direct bottom-end strength. Factory blocks use 2-bolt or 4-bolt main caps. Performance caps often use a 4-bolt splayed design that angles the outer bolts outward into thicker material.

Milodon main caps fit small-block Chevy 283-327 engines. A main cap girdle ties the caps together into one structure to reduce cap movement at high rpm. Speedmaster main cap girdles fit big-block Chevy 454, small-block Chevy 350, and big-block Ford 429/460 engines.

Pair new caps with fresh main bearings and upgraded main studs and bolts. Then torque everything to spec with our small-block Chevy torque specs and casting numbers or big-block Chevy engine torque specs. For LS main caps, check the bolt values in our Chevy LS engine torque specs guide.

What Do Oil Restrictors and Block Hardware Do?

Oil restrictors limit oil flow to the lifter galleries and top end, so more oil stays available for the crankshaft bearings. Moroso oil restrictors fit small-block Chevy and Ford 351C, 429, and 460 engines. Allstar Performance oil restrictors fit standard Chevy blocks.

Block hardware covers the small parts that keep an assembly aligned and serviceable. Check these items during teardown, since a worn pin or missing deflector is easy to overlook. You'll find Moroso bellhousing dowel pins in .014" and .021" offsets, an oil pressure relief valve deflector for LS-series engines, and magnetic differential plugs.

Refreshing the whole engine at once? Shop engine rebuild kits now to order the rest of your rebuild in one step.