What to Look For in 5.7 Hemi Valve Cover Gaskets
TL;DR: On a Gen III 5.7 Hemi the valve cover is not just a lid. It carries the ignition coils, it forms the spark plug tubes for sixteen plugs, and on later engines it houses crankcase ventilation hardware. That means a "valve cover gasket" on this engine is really a gasket system: the perimeter seal, the spark plug tube seals, and the bolt grommets that control how much the cover is allowed to move. Buy a set that includes all three in one molded piece, made from a material that survives underhood heat cycling, and confirm the part number against the manufacturer catalogue for your exact year and cover style before you order.
Why this gasket matters more on a Hemi than on a typical V8
The Gen III Hemi is a pushrod, overhead-valve V8 with two spark plugs per cylinder — sixteen plugs total. Each bank carries a row of coils that bolt to the valve cover, with short leads crossing to fire the second plug in each chamber. The plugs sit down in wells formed by the cover itself.
Stack that up and the consequences of a marginal seal get expensive fast:
- Oil in the spark plug wells. A failed tube seal fills the well with oil. The coil boot swells, tracks, and starts misfiring. You chase a misfire, replace a coil, and the new coil dies too, because the well is still full of oil.
- Coil hardware pulling on the cover. The coils are fastened to the cover. Every time someone works on the ignition system, that hardware gets loaded. A cover that is warped or a bolt boss that has been over-torqued will not clamp the perimeter gasket evenly.
- Crankcase ventilation. Later 5.7 Hemis integrate ventilation hardware into the cover assembly rather than using a simple grommet-and-valve arrangement. If your engine is one of them, a restricted or failed ventilation path raises crankcase pressure and will push oil past a gasket that is otherwise fine. Confirm which arrangement your model year uses before you assume the gasket is the culprit.
- Access. One side is usually straightforward. The other is buried behind accessory brackets, lines and heat shielding depending on the chassis. You do not want to do this job twice.
Start with parts filtered to the platform: 5.7 Hemi parts and the broader gaskets and seals category.
The four things a good set actually gets right
1. One molded piece, not a stack of separate rings
The best sets are a single molded elastomer carrier: perimeter seal, plug tube seals and bolt grommets all in one part that drops into the cover channel and stays there while you flip the cover over. Cheaper sets ship the perimeter as one piece and the tube seals loose, which means you are aligning eight small seals in a groove on a part you cannot see once it is on the engine.
If a set does ship the tube seals separately, that is not automatically a reject — but you need to confirm they seat fully and stay seated before the cover goes near the head.
2. Material that survives heat cycling, not just first fit
Everything seals when it is new. What matters is what the material looks like after several hundred heat cycles. Look for a molded synthetic rubber compound rated for engine oil and sustained underhood temperature. Avoid anything cork-based or paper-faced on this engine — the cover geometry and the tube seals need an elastomer that recovers, not a compressible pad that takes a set and stays there.
The practical test on the part in your hand: press a tube-seal lip with a thumbnail. It should spring back cleanly. If it stays dented, it will not follow a plug tube through a cold-start-to-highway temperature swing either.
3. Bolt grommets and sleeves included
The valve cover fasteners on this family run through grommets — often with a metal crush sleeve or limiter — that set the final clamp height. Those grommets are a wear item. They harden, they lose recovery, and a hardened grommet lets the cover chatter against the head.
A set that includes fresh grommets and limiters is worth more than one that does not, even at a higher price, because reusing 150,000-mile grommets is the most common reason a brand-new gasket leaks within a year.
4. A part number that matches your cover
Cover design, ventilation hardware and coil mounting changed over the production life of this engine. A gasket that fits one revision may sit proud of the channel on another. Match the part number to your model year, engine and cover style using the manufacturer catalogue — do not order from a photo, and do not assume both banks take the same part number. Several applications use bank-specific covers and bank-specific gaskets.
What to look for: comparison table
| What you are evaluating | Good sign | Walk away |
|---|---|---|
| Construction | One molded carrier with perimeter, tube seals and grommets integrated | Loose rings in a bag with no carrier |
| Material | Molded synthetic rubber rated for oil and underhood temperature | Cork, cork-rubber composite, paper-faced |
| Tube seals | Full-depth lips that spring back under thumbnail pressure | Thin, hard, or already deformed in the packaging |
| Bolt hardware | Grommets and crush limiters included | Gasket only, "reuse existing grommets" |
| Coverage | Explicit year, engine and bank-specific listing | "Fits all Hemi" with no year breakdown |
| Documentation | Torque sequence and RTV callouts referenced to the service manual | No instructions at all |
| Extras | Matching plug tube seals sold as part of the same set | Tube seals sold separately as an upsell |
Installation details that decide whether it holds
Buying the right set is half the job. The other half is what you do with it.
Clean, but do not gouge. The sealing surfaces on the head and the cover must be free of old sealant and oil film. Use a plastic scraper and a solvent that flashes off clean. A steel blade on an aluminum head — or on a composite cover — leaves scratches that become leak paths, and it drops debris into the valvetrain.
Respect the corners. Where the timing cover meets the cylinder head, many procedures on this family call for a small bead of RTV at the junction before the cover goes on. Check the service manual for your model year for whether your engine needs it, where exactly it goes and how long you have to seat the cover before the sealant skins.
Torque low, torque in sequence, torque with a real wrench. Valve cover fasteners on this engine are a low inch-pound specification, tightened in a defined pattern from the center outward. This is the single most common place people ruin a fresh gasket. Torque in the factory sequence to the value in the service manual for your year — do not guess, and do not use a foot-pound wrench at the bottom of its range. If your cover is composite, over-torque does not just crush the gasket; it strips the boss the coil hardware threads into.
Inspect the coils while you are in there. If the wells were full of oil, the boots have already been soaking. Clean the wells out completely and replace any boot or coil that is swollen, cracked or carbon-tracked. There is no benefit to a perfect new seal under an ignition system that is already contaminated. Browse ignition components while the cover is off.
Have the right tools staged. A low-range inch-pound torque wrench, a proper plug well cleaning method, and the extensions needed for the buried side. Check engine stands and tools if you are short something.
What this job typically costs in shop time
Independent shops generally book this as a modest job on the accessible bank and a longer one on the buried bank, with the total commonly landing in the low-single-digit labour-hour range for one side and higher when both sides are done together or when accessory removal is required for access. Doing both banks in one visit is almost always cheaper than doing them separately, and it is the right call if the engine has enough miles that one side has already failed.
If the shop finds contaminated coils, plugs due for replacement, or a crankcase ventilation problem, expect that to be quoted on top — and it is legitimate work, not an upsell, if the wells were full of oil.
Frequently Asked Questions
How do I know my 5.7 Hemi valve cover gasket is actually leaking? The two clearest signs are oil pooled in the spark plug wells when you pull a coil, and oil weeping down the outside of the head below the cover rail. A misfire on one cylinder that comes back after a coil replacement points at a flooded well rather than a bad coil.
Do I need to replace both valve cover gaskets at the same time? Not mechanically — each side seals independently. But if one has failed at high mileage, the other is the same age under the same heat, and the labour overlap means doing both in one visit usually costs less than two separate jobs.
Can I reuse the old bolt grommets to save money? You can, but it is the most common reason a new gasket leaks quickly. The grommets set clamp height, and old ones harden and stop recovering. Buy a set that includes them.
Does the 5.7 Hemi need RTV as well as the gasket? On many applications in this family a small bead is called for at the timing-cover-to-head junctions. Whether yours needs it, and exactly where, is a service-manual question for your model year — the gasket alone does not always cover those corners.
What torque do the valve cover bolts take? It is a low inch-pound value applied in a specific sequence, and it varies by year and cover material. Torque in the factory sequence to the value in the service manual for your engine. Over-torquing a composite cover strips the coil mounting bosses and distorts the sealing rail.
Will oil in the plug wells damage the spark plugs themselves? The plugs usually survive, but the coil boots do not — they swell and track, which causes the misfire. Clean the wells fully, replace contaminated boots or coils, and inspect the plugs while they are out.
How long should a quality 5.7 Hemi valve cover gasket set last? A properly selected molded set, installed on clean surfaces with fresh grommets and correct torque, is a long-service repair rather than a maintenance item. Premature repeat failures almost always trace back to reused grommets, incorrect torque, or unresolved crankcase pressure.
Sources
- Core Powertrain Parts catalogue and Gen III Hemi fitment data, used to confirm collection coverage and platform categories.
- Core Powertrain Parts internal tech articles on Gen III Hemi service and on valve cover sealing across other engine families.
- Shop experience with Gen III Hemi ignition-well oil contamination and coil boot failure.
- Torque values, tightening sequences and RTV placement are deliberately not reproduced here — confirm them in the factory service manual for your model year, and confirm the current part number against the manufacturer catalogue before ordering.