LQ4 vs LM7: Which Junkyard LS Is the Better Buy?
With the same parts in the same car, an LQ4 6.0 makes about 30–50 more horsepower than an LM7 5.3, and it usually costs a few hundred dollars more to buy used.
Both are iron-block, Gen III truck engines from 1999–2007, and both use the same 24x computer and wiring. The real differences are displacement, bore size and price.
Side by side
| LM7 5.3 | LQ4 6.0 | |
|---|---|---|
| Years | 1999–2007 | 1999–2007 |
| Came in | Silverado, Tahoe, Yukon | 3/4-ton trucks, vans, Yukon |
| Block | Iron | Iron |
| Factory power (common figure) | 295 hp / 335 lb-ft | 325 hp / 370 lb-ft |
| Compression | 9.5:1 | 9.4:1 |
| Bore | 3.78" | 4.00" |
| Crank trigger | 24x | 24x |
| Typical used price | $900 | $1,300 |
Same parts, same car: what you get
Each row is the same build in a G-body, priced with used parts and your own labor.
| Build | LM7 5.3 | LQ4 6.0 | LQ4 difference |
|---|---|---|---|
| Stock | 305 hp · $7,120 | 335 hp · $7,570 | +30 hp · +$450 |
| Stage 2 cam | 375 hp · $8,395 | 405 hp · $8,530 | +30 hp · +$135 |
| Single turbo, 8 psi | 427 hp · $11,200 | 470 hp · $11,600 | +43 hp · +$400 |
| Cam + turbo, 12 psi | 568 hp · $12,868 | 618 hp · $13,718 | +50 hp · +$850 |
The LQ4's lead grows with boost, because boost multiplies whatever displacement you start with.
What the numbers don't show
- Bigger heads need the bigger bore. L92 and LS3 rectangle-port heads have valves too big for the LM7's 3.78-inch bore. The LQ4's 4.0-inch bore takes them, which is one of the best junkyard power upgrades.
- Boost: both take moderate boost on stock internals. The LQ4 has slightly lower compression and more displacement, which is why turbo builders hunt for it.
- Weight: some 1999–2000 LQ4s have iron heads, which adds weight over the nose.
- Availability: LM7s are in every junkyard. LQ4s come from 3/4-ton trucks and vans, so they take more looking.
Which one to buy
Buy the LM7 if you want the cheapest engine that's everywhere, for a mild street build. Buy the LQ4 if you plan to add boost or a head swap, or the price gap is small where you live.
- Find an LM7 5.3SummiteBayAmazon
- Find an LQ4 6.0SummiteBayAmazon
- Test it before you pay with a compression tester.SummiteBayAmazon
Sources
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