2007.5-2010 GMC Duramax LMM Valve Covers

Scoping the job on a 2007.5-2010 Sierra HD

Think of this collection in three depths. The shallow job is a cover coming off and going straight back on: a gasket set, the grommets at the fasteners, fresh bolts. The middle job is a cover off to reach something else, whether that is injectors, glow plugs or wiring down in the valley, where you are buying sealing parts to finish another repair properly. The deep job is heads off, and that is where the full engine gasket set, the head set and the valve stem seal kit come in, along with a spring compressor and a bench to work on. Buy for the depth you are actually going to, not for the deepest one listed here.

What fails and why

The honest answer is that the LMM top end does not have a known failure. Hydraulic roller lifters, a camshaft that lives down in the block and four valves per cylinder add up to a valvetrain with no documented LMM-specific failure pattern, so what is on this page is service and teardown hardware rather than a fix for a weak design. The gaskets and seals themselves are consumables. They come out because they were disturbed, because a decade of heat cycles has taken the spring out of them, or because a deeper repair opened the joint they were sealing. Valve stem seals belong to that last group; they are a bench-depth item, not a driveway fix.

Stock replacement vs. upgrade

There is not much to upgrade in a sealing job, and that is fine. Mahle sets put the factory sealing back the way GM specified it, and Merchant Automotive grommets plus an Alliant Power head installation gasket kit cover the small parts that are easy to forget until the job stalls. ARP bolt kits are the one piece worth thinking about: stainless or black oxide hardware, clean threads and an even pull across the cover, which is worth more on a truck that has had the covers off before. An XDP billet oil fill cap swaps a handled plastic part for metal. A catch can that gets serviced on a schedule is the only add-on that touches this area, and it does its work with the factory closed-crankcase routing left in place.

What we carry

At the shallow end, Mahle valve cover gasket sets for the 2007.5-2010 trucks and for the wider 2004.5-2010 range, Merchant Automotive upper valve cover grommets, ARP stainless steel and black oxide valve cover bolt kits, and an XDP billet engine oil fill cap. A step deeper, a Mahle lower rocker cover gasket set and an Alliant Power cylinder head installation gasket kit. At teardown depth, a Mahle head set and a full engine gasket set, both listed without the head gasket, plus a Mahle valve stem seal kit. Everything else for this platform is on the Duramax hub.

Fitment notes

Part ranges in here do not line up neatly. Some sets are listed 2007.5-2010, others 2004.5-2010, and the bolt kits run 2004.5-2016 Duramax, because fasteners crossed generations that castings did not. Go by the engine code. The 2007 Sierra Classic HD is the previous GMT800 body with the LBZ, so an early 2007 truck does not automatically belong on this page, and 2011 is a harder break: the Sierra Denali HD arrived that year on a new frame with the LML engine, so treat 2011-and-newer fitment as a separate question. Grommets and bolt kits are sold apart from the gasket sets. Check your VIN in the fitment checker when a listing's range and your truck do not obviously agree.

Frequently asked questions

What is a valve stem seal kit, and when would I need one?

Valve stem seals ride on the valve stems inside the head and keep oil from drawing down past them. They are not a maintenance item on an LMM, and there is no documented pattern of them failing on this engine, so you would buy a set because the heads are already off for other work and the valves are out. If your heads are still on the truck, this is not the part you are looking for.

Only one bank is leaking. Should I do both sides?

The covers are per-bank parts, so mechanically you can do one. In practice, if the truck has enough miles to push oil past one gasket, the other side is the same age, and the labor to be in there a second time costs more than the second gasket. Read what the kit you are ordering actually includes, because some sets cover one application and others cover both covers on a bank.

Do ARP bolt kits do anything on a stock Sierra?

Nothing for power. What they give you is fresh fasteners, clean threads and an even torque across the cover, which matters most on a truck whose covers have been off and back on a few times. The stainless and black oxide versions are the same idea in different finishes. If the original bolts are in good shape and the covers have never been off, the factory hardware is not a problem.

Will anything here fit a 2011 Sierra Denali HD?

Only the parts listed that far. The bolt kits run through 2016 Duramax and cross over, while the gasket sets listed 2007.5-2010 or 2004.5-2010 do not. 2011 brought the LML engine and a revised HD chassis, so check the engine RPO code and let the fitment checker confirm the listing 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.