If you've spotted a greasy mess or smelled burning oil lately, your ls valve cover gasket is likely the culprit and needs a quick swap. It's one of those jobs that seems annoying when you first see the smoke coming from under the hood, but it's actually one of the easiest DIY fixes you can do on an LS-based engine. Whether you're running a 5.3 in a high-mileage Silverado or a cammed LS3 in a weekend toy, those rubber seals eventually give up the ghost.
Let's be honest, the LS platform is legendary for its reliability, but it isn't bulletproof when it comes to leaks. Over time, the constant heat cycles of the engine turn that once-supple rubber into something that feels more like brittle plastic. Once it loses its ability to squish and seal, gravity does the rest, and oil starts weeping down the side of the head. If you're lucky, it just makes a mess. If you're unlucky, it drips right onto your hot exhaust manifolds, giving you that lovely "old truck" fragrance every time you hit a red light.
Why These Gaskets Start Leaking in the First Place
The LS engine uses a pretty clever design for its valve covers. Unlike older small blocks that used a bunch of bolts around the perimeter, the LS mostly uses center-bolt covers with a deep groove for the gasket to sit in. This usually provides a great seal, but time is the enemy of all things rubber.
Most of the time, it's just age. If your engine has 150,000 miles on it, those gaskets have lived a long life. However, sometimes high crankcase pressure can speed things up. If your PCV (Positive Crankcase Ventilation) system is clogged or if you're running a lot of boost without a proper catch can setup, that pressure has to go somewhere. Often, it tries to push its way past the ls valve cover gasket, creating a leak even if the rubber is still technically "good."
Another common reason for leaks is actually human error. I've seen plenty of guys pull their valve covers to swap rockers or springs and then try to reuse the old, flattened gaskets. While the LS gaskets are technically "reusable" if they're still soft, it's usually not worth the risk. For the price of a new set, you might as well just do it right the first time so you don't have to pull everything apart again in two weeks.
How to Tell if Yours Are Shot
The most obvious sign is the smell. Oil hitting a hot exhaust manifold has a very specific, acrid scent that you can't miss. If you open the hood after a long drive and see a little wisp of blue smoke coming from the back of the engine bay, you've found your problem.
You should also look for "wet" spots on the cylinder heads. Since the LS engine sits at a slight angle and the valve covers are tilted, the oil tends to pool at the back of the head near the firewall. Get a flashlight and look past the coil packs. If the area around the spark plugs looks dark and gunked up with dirt and oil, your ls valve cover gasket has left the chat.
Don't confuse a valve cover leak with a leaking oil pressure sensor, though. On many LS engines, the oil pressure sensor is located at the back of the valley cover. When it leaks, it can spray oil down the back of the block, which looks a lot like a valve cover leak. A quick wipe-down and a few minutes of idling should help you pinpoint exactly where the wetness is starting.
Tools You'll Need for the Job
One of the best things about working on an LS is that you don't need a massive tool chest to get things done. For a gasket swap, you're looking at some pretty basic stuff:
- A 10mm socket (the MVP of any engine work).
- A small flathead screwdriver or a pick tool.
- Some brake cleaner and a few clean rags.
- A torque wrench (if you want to be precise, though many people just wing it).
- A set of new ls valve cover gaskets.
If you're working on a truck or a car with a lot of stuff in the way, you might need an extension for your ratchet to reach the back bolts. Other than that, it's a very straightforward "in and out" type of project.
The Step-by-Step Process
First off, make sure the engine is cool. You're going to be leaning over the fenders and touching the top of the heads, and there's no reason to give yourself a souvenir burn.
Clearing the Way
Before you can get to the valve covers, you have to deal with the coil packs. On an LS, the coils are mounted to a bracket that sits right on top of the cover. You can technically remove the coils individually, but it's way faster to just unbolt the whole bracket as one unit. Unplug the main harness connector and the spark plug wires, then remove the five 10mm bolts holding the bracket down. Set the whole assembly aside.
Removing the Old Gasket
Now that the cover is bare, loosen the four long bolts in the center. These bolts actually stay "trapped" in the cover by rubber grommets, which is a nice touch because it means you won't drop them into the abyss of the engine bay. Once the bolts are loose, wiggle the cover until it breaks free.
Flip the cover over on your workbench. You'll see the old ls valve cover gasket tucked into a channel. Use your pick or screwdriver to pop it out. This is the part where you'll probably notice how hard and brittle the old rubber has become.
Cleaning Is Key
I can't stress this enough: don't skip the cleaning. If you put a brand-new gasket onto a dirty, oily surface, it might not seat properly. Take a rag soaked in brake cleaner and wipe down the "mating surface" on the cylinder head. You want it to be shiny and dry. Then, do the same for the groove in the valve cover itself. Make sure there's no old gunk or debris sitting in that channel.
Installing the New Seal
Take your new ls valve cover gasket and press it into the channel of the valve cover. It should fit snugly. A little trick is to start at the corners (or the "humps" for the rockers) and then work your way around. Make sure it's seated evenly all the way around and isn't pinched anywhere.
Now, check the rubber grommets on the bolts you loosened earlier. These grommets are actually part of the sealing system. If they're cracked or squashed flat, they can let oil seep out from the bolt holes. Most high-quality gasket kits come with new grommets, so go ahead and swap them out while you're at it.
Putting It All Back Together
Carefully set the valve cover back onto the head. You might have to wiggle it a bit to make sure the gasket stays in its groove as you lower it down. Once it feels seated, start the four center bolts by hand.
Pro-tip: Don't over-tighten these. The torque spec for LS valve cover bolts is usually only about 106 inch-pounds (which is only about 9 foot-pounds). If you crank down on them like you're tightening lug nuts, you can actually distort the cover or even crack the aluminum. Just get them "snug plus a little bit" and you'll be fine.
Reattach your coil pack brackets, plug in your harness, and snap those spark plug wires back on. Double-check that everything is plugged in, or you'll be greeted by a blinking check engine light as soon as you start the car.
Wrapping Things Up
Once everything is buttoned up, fire up the engine and let it run for a few minutes. Take a flashlight and look along the edges of the covers. If everything looks dry, you're golden. It's also a good idea to spray down the side of the engine with some degreaser to get rid of the old oil. That way, you'll know for sure if a new leak pops up later.
Changing an ls valve cover gasket isn't a "glamour" mod. It won't add 50 horsepower, and nobody at the car show is going to ask to see your new seals. But in terms of basic maintenance, it's one of the most satisfying things you can do. It stops the smells, stops the smoke, and keeps your engine looking as good as it runs. Plus, it gives you an excuse to get out in the garage for an hour or so—and that's never a bad thing.