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Any junkyard tricks for finding a real 6.0?

  • Look at 3/4-ton trucks, vans and big SUVs. The Gen III iron-block 6.0 (LQ4/LQ9) came in the heavier-duty trucks, cargo vans and SUVs, while the half-ton trucks mostly got the 4.8 and 5.3. For example, 1999–2007 Silverado/Sierra 2500 3/4-tons had the LQ4. Our LQ4, LQ9 and LY6 pages list the donor vehicles.
  • Read the glovebox label. The Service Parts Identification sticker lists the engine RPO and VIN code. For 2018 and newer, it's a QR code on the door-jamb label.
  • Know the oddballs: 1999–2000 LQ4s came with cast-iron heads (casting numbers 373 and 873), and the LQ9 uses flat-top pistons for about 10:1 compression.
  • 1999–2000 6.0s have a "long" crankshaft flange, which changes which flexplate/transmission combinations bolt up. That matters if you're planning a 4L60E.

Last updated

Confirm with the donor finder.

What we recommend

Our favorite hunting ground is 2001-and-up Escalades and Denalis, because their 6.0s were always LQ9s. Sellers often label LQ4s as LQ9s to charge more, so we recommend verifying with the donor VIN; a GM dealer can decode the last 8 digits to ID the engine. Keep in mind that 99-00 6.0s have a longer crank that limits transmission choices. Keep the MAP, crank and cam sensors and the coil wiring even if you're going carbureted, because you'll want them later.

Check this first:

  • Have a GM dealer decode the last 8 of the donor VIN
  • Bore-scope the cylinders
  • Pull the pan and valve covers and check the existing fluids

Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk.

Go deeper

Check this first

  1. Have a GM dealer decode the last 8 of the donor VIN
  2. Bore-scope the cylinders
  3. Pull the pan and valve covers and check the existing fluids

Try this, then this

  1. Hunt 2002+ Escalade/Denali donors first — always LQ9 per application list. Worked if: VIN 8th digit is N
  2. Verify any claimed LQ9 by VIN + piston check — LQ4s are routinely sold as LQ9s. Worked if: flat-top pistons or N VIN confirmed

How you know it's fixed

  • VIN decodes to N-code LQ9; crank flange measures 0.857 in on 2001+

Still not fixed?

  • A '99-00 long-crank 6.0 limits trans choices - budget for a spacer/flexplate solution

Key numbers

WhatValue
1999-2000 6.0 crank flange thickness1.25 in (long crank)
2001-up 6.0 crank flange thickness0.857 in (standard)
LQ9 applications2002-2006 Escalade, Silverado SS, VortecMAX
LQ9 vs LQ4higher-output LQ4, flat-top pistons, 10:1

Every option we know of

Maker / productPart #FitsPriceWhereStatus / notes
GM
99-00 long-crank 6.0 crankshaft (1.25 in flange)		n/a

Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.

Time and cost: A day at the yard with tools

How do I find the block casting number and date code on a 6.0 LS block?
What we recommend

The casting number is on the driver's-side rear of the block below the head, and the date code is at the front of the block below the passenger-side head. With the engine in the vehicle you may need a flashlight and a mirror to read the casting number; a common 6.0 example is 12551364. The date code is four characters: the letter is the month, the next two digits are the day, and the last digit is the year, so F203 means June 20, 2003. We recommend decoding both together, since that pins down what you're actually buying and which parts to order for it.

Check this first:

  • Flashlight and mirror for reading the rear casting in the vehicle

Check this first

  1. Verify the date-code location on your specific block - don't assume the row's location

Try this, then this

  1. Read casting + date code at the rear driver side — standard location. Worked if: code decodes cleanly

How you know it's fixed

  • Date code read and decoded

Key numbers

WhatValue
Date code formatletter = month, digits = day + year digit
Casting number locationrear driver side of block

Time and cost: 10 minutes with a light

What should I check on a junkyard 6.0 before paying for it?
What we recommend

Before you pay, we recommend running a compression check if you can, cutting open the oil filter, and looking inside the pan for wear debris. If possible, pull the valve covers and pan too. Salvage engines regularly turn up tweaked valves, broken rings and valve springs, worn cam lobes, failed lifters, bent pushrods and water damage. Our rule is simple: never install a salvage LS without either hearing it run or going completely through it. Factor in machine work, since full short-block machine work quotes have ranged from $850 to $2,500+.

Check this first:

  • Run a compression check
  • Cut open the oil filter and inspect the pan for debris
  • Pull the valve covers to check lifters, pushrods and springs
  • Look for signs of water in the oil or cylinders

Careful: Installing an uninspected junkyard engine risks a failure that costs far more than the teardown would have.

Check this first

  1. Magnaflux and measure before spending - a cracked block makes the machine bill moot

Try this, then this

  1. Get an itemized quote (mag, bore, hone, deck, head refresh) before authorizing — machine bills creep. Worked if: total lands $850-2,500

How you know it's fixed

  • Machine work done within the $850-2,500 window

Still not fixed?

  • If the quote exceeds $2,500, price a reman short block instead

Key numbers

WhatValue
Machine shop services pricingalign-hone, bore/hone, deck, head work itemized

Every option we know of

Maker / productPart #FitsPriceWhereStatus / notes
Golen Engine Service
machine shop services		n/aLS blockssee price listgolenengineservice.comIn production

Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.

Time and cost: 2-4 weeks typical shop turnaround

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