2007.5-2010 Chevy Duramax LMM Valve Covers

How the top end seals on the 2007.5-2010 Silverado LMM

The LMM is an overhead-valve, cam-in-block V8 with hydraulic roller lifters and four valves per cylinder, so the camshaft stays down in the block and never passes through the covers. What the covers close off is the rocker area on top of the cast aluminum heads: a lower rocker cover against the head, an upper cover above it, and grommets at the fasteners. The engine also runs closed crankcase ventilation, with crankcase vapor routed back into the intake instead of out a breather, so the top end is a sealed system and it has to go back together that way. Everything in this collection is about restoring that seal the way GM built it.

What fails and why

GM did not leave a documented valvetrain weak spot in the LMM. There is no LMM-specific lifter, rocker or valve failure pattern in the record, which is why this page is sealing hardware rather than repair parts. Most of it gets ordered because the covers are already coming off for something else, whether that is injector work, glow plugs or a head job, and nobody wants to reuse a gasket that has been torqued down through ten years of heat cycles. Grommets and bolts fall in the same category: cheap, in the way, and not worth a second trip into the same job.

Stock replacement vs. upgrade

Factory-style sealing is the right call on almost every truck here. Mahle gasket sets replace what came off in the correct material and thickness, and Merchant Automotive upper cover grommets go back in with them. The two optional pieces are hardware and dress-up. ARP valve cover bolt kits in stainless or black oxide give you fresh fasteners and an even torque across the cover, and a billet oil fill cap from XDP replaces a plastic part that gets handled at every oil change. If oil mist in the charge air is what brought you here, a catch can that actually gets serviced handles that while leaving the factory closed-crankcase routing in place.

What we carry

Mahle valve cover gasket sets listed for 2007.5-2010 and for the wider 2004.5-2010 range, a Mahle lower rocker cover gasket set, and a Mahle head set and full engine gasket set, both without the head gasket; an Alliant Power cylinder head installation gasket kit; Merchant Automotive upper valve cover grommets; ARP stainless steel and black oxide valve cover bolt kits; and an XDP billet engine oil fill cap. Other systems on this truck are on the Duramax hub.

Fitment notes

Listings here spread across 2007.5-2010, 2004.5-2010 and 2004.5-2016 Duramax, because some of this hardware is specific to the LMM while bolts and lower covers carry across several RPO codes. Shop by engine code, not by model year. Grommets are separate line items from the gasket sets, so read what a kit includes before assuming it is complete. The 2007 Classic Silverado HD is the older GMT800 body with the LBZ engine, so an early 2007 truck needs to be identified before you order. When it is not obvious, run the VIN through the fitment checker on any product page.

Frequently asked questions

Which gasket set do I actually need?

It depends on which cover is coming off. A valve cover gasket set covers the upper cover, while the lower rocker cover gasket set is a separate part that seals against the head itself. If the job goes deeper, with heads off or injectors out, the full engine gasket set or the head set covers more of those joints in one order. Tell us what the job is and we will point you at the one that stops in the right place.

Why do the head set and the engine gasket set say "without head gasket"?

Because head gaskets on this engine are ordered per bank and by thickness grade, so they cannot be bundled into a general set. The A, B and C letters on an LMM head gasket are thickness steps, not quality steps, and the right grade comes from what your engine measures once it is apart. Those sets cover everything else, and you add the graded gaskets separately.

How much of a reseal should I do while the covers are off?

More than you might plan on, within reason. Gaskets, grommets and fasteners that are already exposed are cheap next to pulling the same parts twice, so a cover gasket with its grommets and bolts is a normal single order. Going past that, into the lower cover or head-level joints, should be driven by what you find when it is open rather than by whatever a kit happens to include.

Will these fit a 2007 Classic Silverado 2500HD?

Some of them will, but check first. The Classic is the previous GMT800 body with the LBZ, and several parts here are listed from 2004.5, which covers both engines. The LMM-specific sets that start at 2007.5 do not. Look up the engine RPO code or use the fitment checker before you order.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.