Recipe - Duramax 6.6L V8 Turbo Diesel (GM HD, LB7-LMM 2001-2010)

Specific Fix build

Reliability tier: aggregated - verify before ordering, see /disclosure/

Head-gasket replacement path (Head gasket failures (higher mileage / load)): stock gaskets age and elevated cylinder pressures finish them. The LB7/LLY OEM gaskets are grade-coded (A/B/C x side, 12637785-90) - the grade is chosen from piston protrusion measurements at teardown, not guessed. The later generations carry OEM 'less head gaskets' kits (98403365 LLY, 98434773 LBZ/LMM) alongside the gaskets themselves; aftermarket Solid Seal kits bundle upper gaskets + Grade-C gasket + 220ksi studs (Dave's, California-excluded). Stock head bolts are torque-to-yield: replace with new bolts or upgrade to studs.

Parts

Duramax LB7/LLY Cylinder Head Gasket, Grade-Coded (OEM) - grade-coded OEM head gaskets for LB7/LLY - aliases carry all six PNs (grade A/B/C x L/R); grade from measured piston protrusion (qty 1)
Duramax LLY Cylinder Head Gasket Kit, Less Head Gaskets (OEM) - OEM upper/lower gasket kit without head gaskets (LLY) - the rest of the job's sealing (qty 1)
Duramax LBZ/LMM Cylinder Head Gasket Kit, W/O Head Gaskets (OEM) - OEM 'w/o head gaskets' kit for LBZ/LMM (qty 1)
Duramax 6.6L Head Stud Kit (LB7-LMM 2001-2010) - stud kit replaces single-use TTY head bolts; two live Dave's options (custom-age $647.66, PPE $539.99) (qty 1)
Duramax LB7 Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket - aftermarket bundled kit (gasket Grade-C + studs) for LB7; California-excluded per seller (qty 1)
Duramax LBZ Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket - same bundled kit for LBZ (qty 1)
Duramax LMM Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket - same bundled kit for LMM; MY2007 build-date caveat (qty 1)
Duramax Engine Oil Cooler Assembly (OEM) - while the cab/engine is opened at this mileage: inspect the oil cooler - the classic cross-generation cooling service item (different job, same teardown window) (qty 1)

Install order

measure piston protrusion, select gasket grade (LB7/LLY)
verify generation by VIN at the 2004/2007 switches
remove heads; machine/inspect decks
fit gaskets + new studs or new TTY bolts
assemble with the generation's OEM kit gaskets

Expected outcome

sealing restored across the heat cycles; no coolant loss or compression cross-bleed

Do not

do not guess the gasket grade - protrusion measurement decides it on LB7/LLY
do not reuse torque-to-yield head bolts - they are single-use by design
do not skip deck flatness checking on a truck that cooked the gasket

Parts budget

About $790-$1,150 in parts. It depends on what the diagnosis finds; each option below is what you buy together. Prices marked "at Dave's" are Dave's Auto Center's, the same as in his store; the others are approximate prices from OEM and maker catalogs, rounded (a manufacturer's list price can run higher). Parts only, no labor.

about $1,050-$1,150: Duramax LB7/LLY Cylinder Head Gasket, Grade-Coded (OEM) (about $55) + Duramax LLY Cylinder Head Gasket Kit, Less Head Gaskets (OEM) (about $420) + Duramax 6.6L Head Stud Kit (LB7-LMM 2001-2010) ($539.99 at Dave's)
about $970-$1,100: Duramax LBZ/LMM Cylinder Head Gasket Kit, W/O Head Gaskets (OEM) (about $430) + Duramax 6.6L Head Stud Kit (LB7-LMM 2001-2010) ($539.99 at Dave's)
$789.00: Duramax LB7 Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket ($789.00 at Dave's)
$789.00: Duramax LBZ Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket ($789.00 at Dave's)
$789.00: Duramax LMM Head Gasket Kit - Solid Seal, w/ Grade-C Head Gasket ($789.00 at Dave's)

DIY or shop: Shop: this is a full head-off job with machining decisions - not DIY territory.