A 350 small block valve cover is a metal or composite lid that bolts onto the top of your cylinder head to seal the valve train area and prevent oil from leaking out during engine operation.
The Chevrolet 350 small block is one of the most common V8 engines in American vehicles, and the valve covers are among the most frequently replaced or upgraded parts on that engine. They sit directly above the rocker arms and pushrods, which need oil circulation to function. Without a tight seal, oil escapes onto the engine block, spark plug wires, and exhaust manifolds — creating mess, smell, and potential fire risk.
Valve covers come in different materials, heights, and designs depending on your engine year, vehicle type, and what other components are already installed under the hood. Choosing the right one means understanding what your engine needs, what space you have, and whether you want stock appearance or a custom look.
Key Takeaways
- Stock 350 valve covers are designed to fit specific years and engine variations, so you need to know your engine's exact year and block type before ordering.
- Aftermarket valve covers come in aluminum, steel, and composite materials, each with different costs, durability, and appearance trade-offs.
- Tall valve covers can interfere with air cleaners, headers, or engine bay components, so measure your available space before purchase.
- Gasket material and bolt hole design vary between covers, so a cover that fits one 350 may not seal properly on another without modification.
Stock Versus Aftermarket Valve Covers
Factory Chevrolet 350 valve covers were typically cast iron or aluminum, painted black or orange depending on the year. They are still available through GM parts suppliers and reproduction manufacturers, and they maintain the original engine appearance. Stock covers are usually the cheapest option and fit without modification, but they can be harder to clean, more prone to corrosion, and less visually distinctive if you care about engine bay appearance.
Aftermarket covers are made by companies like Edelbrock, Holley, Lokar, and Valve Cover Specialists. These typically offer polished aluminum, powder-coated finishes, custom finning, or engraved designs. They cost more — anywhere from $80 to $400 per pair depending on material and finish — but they seal better, last longer, and let you customize the look of your engine. The trade-off is that some aftermarket designs sit taller or wider than stock, which can create clearance problems.
Understanding Valve Cover Height and Engine Bay Fit
Valve cover height matters because your engine bay has fixed dimensions. A tall cover can hit your air cleaner, hood, or intake manifold. A short cover might not provide enough clearance for the gasket and bolt hardware underneath. Most stock 350 covers are 2.5 to 3 inches tall from the cylinder head surface to the top of the cover.
Before you buy, measure the vertical space above your cylinder head to the nearest obstruction — usually the hood or air cleaner. Then check the product dimensions of the cover you want. Many aftermarket covers list their height in the product description. If you are installing a taller cover, you may need to relocate your air cleaner, modify your intake manifold, or choose a lower-profile design instead.
Width can also be an issue on tight engine bays, especially in older vehicles or those with headers. Lokar and some custom covers have a narrower footprint than stock, which helps in cramped spaces.
Gasket Types and Sealing Performance
The gasket between the valve cover and cylinder head is what actually stops oil from leaking. Stock covers typically use a cork or rubber gasket that compresses when you bolt the cover down. These work but can dry out, crack, or fail after 50,000 to 100,000 miles, especially in hot engines or those that run synthetic oil.
Aftermarket covers often come with modern elastomer gaskets or silicone gaskets, which last longer and resist heat and oil better. Some high-end covers use a molded rubber gasket that is bonded to the cover itself, so you never have to replace it separately. If you are buying an older stock cover used, the gasket is almost certainly worn out and should be replaced before installation.
Bolt hole design matters too. Some covers have studs welded to the cover; others have threaded holes in the cover itself; still others bolt directly to the cylinder head. Make sure the bolt pattern on your new cover matches your cylinder head, or you will have to drill and tap new holes or use adapters.
Material Choices: Aluminum, Steel, and Composite
Aluminum covers are the most popular aftermarket choice. They are lightweight, conduct heat well, resist corrosion, and can be polished or powder-coated to any finish. They cost more than steel but less than some specialty materials. Aluminum is also easier to modify if you need to drill holes for breather fittings or PCV lines.
Steel covers are heavier and more prone to rust, but they are cheaper and can handle higher heat without warping. Some vintage or restoration builds prefer steel to match the original engine appearance. Powder coating protects steel from corrosion, but the coating can chip if the cover is bumped or removed frequently.
Composite or plastic covers are rare on 350 engines but exist on some modern applications. They are lightweight and cheap but offer no aesthetic appeal and can crack in high-heat environments. They are not recommended for performance or show engines.
Breather and PCV Fitting Locations
Your 350 needs a way for crankcase pressure to escape, usually through a breather or PCV (positive crankcase ventilation) line. Stock covers have a hole for a breather tube or PCV hose, typically on one or both covers. When you switch to an aftermarket cover, you need to make sure the hole location matches your existing plumbing, or you will have to reroute hoses or drill new holes.
Some aftermarket covers come with multiple breather boss locations or removable plugs, which gives you flexibility. Others are drilled for a specific setup. If you are building a custom engine or changing your PCV system, measure and plan this before you order the cover, because drilling aluminum or steel after purchase is possible but adds cost and time.
Installation and Bolt Torque Specifications
Installing a valve cover is straightforward: remove the old cover and gasket, clean the cylinder head surface with a gasket scraper, install the new gasket, position the new cover, and bolt it down. The critical step is torque specification — too loose and it leaks; too tight and you crack the cover or strip the bolt holes.
Most 350 valve covers bolt down to 8 to 12 foot-pounds of torque. Check the product documentation or your engine manual for the exact specification. Use a torque wrench and tighten in a crisscross pattern, the same way you would tighten a cylinder head. If the cover has studs instead of threaded holes, use a lock washer under each bolt to prevent loosening from vibration.
After installation, let the engine idle for a few minutes and check for leaks around the gasket perimeter. A small amount of seeping is normal for the first few minutes as the gasket settles, but active dripping means the cover is not sealed properly and needs to be removed and reinstalled.
Frequently Asked Questions
Can I use a 350 valve cover from a different year on my engine?
Sometimes, but not always. Bolt hole patterns and gasket surfaces can vary between years, especially between early (1967–1985) and late (1986–2002) 350 blocks. Check the bolt hole spacing and gasket surface dimensions before assuming a cover will fit. Many reproduction manufacturers make covers for specific year ranges, so ordering the correct year is safer than guessing.
What if my valve cover leaks after I install it?
Remove the cover and check three things: the gasket is seated evenly all the way around, the cylinder head surface is clean and flat with no old gasket material stuck to it, and the bolts are torqued to specification in a crisscross pattern. If the head surface is warped or pitted, you may need to have it resurfaced or use a thicker gasket. If the cover itself is cracked or warped, it cannot seal and must be replaced.
Do I need to replace the gasket every time I remove the valve cover?
Not necessarily, but it is good practice. Cork and rubber gaskets compress and lose their seal after being removed and reinstalled a few times. If you are just doing a quick inspection and plan to reinstall the same cover within a few days, the old gasket may hold. For any longer storage or if you are switching to a different cover, use a new gasket. Modern elastomer gaskets are cheap insurance against an oil leak.
What is the difference between a breather and a PCV valve?
A breather is a straightforward air filter that lets pressure escape but keeps dirt out. A PCV valve is a one-way valve that routes crankcase pressure back into the intake manifold under vacuum. Most modern 350 engines use PCV, but older or carbureted engines may use a breather. Your valve cover needs a hole for whichever system your engine runs, and the hole location must match your hoses.
Can I use a 350 valve cover on a 305 or 327 engine?
The bolt patterns are the same across most small block Chevys (350, 305, 327, 283), so the cover will physically bolt on. However, the gasket surface and bolt hole spacing can vary slightly by year and block type. Test-fit the cover before you buy if possible, or order from a supplier who specifies compatibility with your exact engine year and block code.