Late-model GM small-block V8 engines | Buyer's Guide

By Staff Writer
Sep 5, 2022 | V8, GM, LS6, Buyer's Guide, Engine swap, ls1, vortec, LS, lq4, LS2, LY, Vortec 5300, LQ, LQ9, LY6 | Posted in Shop Work , Buyer's Guides , News and Notes | From the May 2011 issue | Never miss an article

Photography Credits: Courtesy GM (engines), Mick Haupt/Unsplash (store shelf), Colin Wood (illustration)

Story by Liz Miles

The small-block Chevy has been an immensely popular engine since its 1955 release. While many consider this V8 to be a big, fat iron anchor when compared to today’s imported, all-aluminum inline fours, it was a revolutionary engine for its time. 

The original Chevy V8 continued to build power in a reliable package for decades—basically until the turn of this century, when it was finally superseded. In the early ’90s, General Motors assigned their brightest research and development staff members to design a new small-block that could be used across their lineup.

They came up with the first Gen III small-block V8. It was called the LS1. No one could have predicted the popularity this engine would gain after its debut in the 1997 Corvette; by 2001, the Gen III had taken over completely. 

What’s so remarkable about this engine? For one, it was built with the aftermarket in mind. GM gave the engine a low profile so it would easily fit in different cars. The engine is also simple to build and upgrade. The LS engine starts with an aluminum six-bolt main block that is far stronger than any early iron block while weighing about 40 pounds less. With this base, GM built a rotating assembly that can easily support 500 horsepower. 

Superior cylinder head design allows the LS to make big power with stock and aftermarket parts. The engine was built to be assembled like a Lego set, and each piece fits together with dry gaskets. There are four exceptions: the pea-sized globbies found at each corner of the oil pan gasket. 

That first LS was only the beginning. The LS6 came next and featured better-flowing heads, a more radical cam, and a higher-flowing intake manifold for 400 out-of-the-box horsepower. 

[Addressing internet myths about LS swaps]

Iron-block versions of the LS6 were put into trucks and SUVs. They offer more room for bigger bores and usually feature a lower compression ratio, a trait that works well with superchargers and turbos. From there, the line exploded into 650-horsepower models as well as ones fitted with variable valve timing and displacement-on-demand features.

There have now been more than two dozen different LS-series engines. Here are the versions that seem to work best with the gearhead set—and can be easily acquired without destroying your budget. These can be purchased new through GM Performance Parts or found at the local salvage yard. 


The original model received 15-degree, cathedral-port heads that flow excellently. Power adders work well with the 10:1 compression ratio.

  • found in: 1997-2004 Corvette, 1998-2002 Camaro/Firebird, 2004 GTO
  • displacement/compression: 346 cubic in., 10.1:1
  • output: 300-350 horsepower, 320-375 lb.-ft.


Basically an LS1 fitted with even better heads, a bigger cam and a higher-flowing intake manifold. These heads are very impressive for their age.

  • found in: 2001-’04 Z06, 2004-’05 CTS-V
  • displacement/compression: 346 cubic in., 10.5:1
  • output: 385 or 400 horsepower, 385 or 400 lb.-ft.


Call it the iron-block version of the LS6; it was made for the GM truck and SUV line. It has a 4-inch bore that is compatible with the better L92 and LS7 heads. The heads it comes with are similar to those on the LS6, but with a larger combustion chamber. The LQ9 has more compression and a more aggressive camshaft. Great base for real performance.

  • found in: 1999-2004 Silverado, Suburban, Yukon, and Hummer H2 (LQ4); 2002-’06 Escalade; 2003-’07 Silverado SS and Sierra (LQ9)
  • displacement/compression: 364 cubic in., 9.4:1(LQ4), 10.1(LQ9)
  • output: 300 horsepower, 360 lb.-ft. (LQ4), 345 horsepower, 385 lb.-ft. (LQ9)

Vortec 5300

(LM7 Gen III iron, LM4 and L33 Gen III aluminum, LH6 Gen IV aluminum) 

The most plentiful of the Gen III and Gen IV engines, with more than five million cores currently found in North America alone. Choose between the iron- and aluminum-block configurations. Beware: Not all engines named Vortec are Gen III or IV. The one you want is easily identified by a forward-mounted throttle body. The LM4, L33 and LH6 are aluminum-block versions that have 9.5:1 to 9.9:1 compression ratios, meaning power ranges appropriately. The iron LM7 and LY5 have similar compression ratios but feature iron blocks. Avoid the Vortec 4800, though.

  • found in: 1999-and-up mid- and full-sized trucks and SUVs
  • displacement/compression: 325 cubic in., 9.5:1 to 9.9:1
  • output: 280-315 horsepower, 320-338 lb.-ft.


Time for a Gen IV revision to the popular GM V8. LS6 heads are still used, but with a large 4-inch bore and an LS6 camshaft. Compression ratios are up. This one is just now getting old enough to be found in the yards.

  • found in: 2005-’07 Corvette, 2005-’06 SSR, 2005-’06 GTO, 2006-’07 CTS-V, 2006-’09 Trailblazer SS
  • displacement/compression: 364 cubic in./10.9:1
  • output: 400 horsepower, 400 lb.-ft.


This is the Gen IV answer to the iron-block LQ4/LQ6 engines. Variable valve timing bumps the output. In a few years, this will be a junkyard score. Iron block plus low compression: Boost, anyone?

  • found in: 3/4-ton 2007-and-up Silverado, Sierra, Suburban and Yukon
  • displacement/compression: 364 cubic in., 9.67:1
  • output: 353 horsepower, 373 lb.-ft.
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View comments on the GRM forums
7/11/22 1:46 p.m.

quiero hacerle un swap a mi pontiac fiero gt 1986 y deseo saber sobre los motores y accesorios que tengan disponibles 

Noddaz GRM+ Memberand UberDork
7/11/22 6:27 p.m.

Bienvenido a bordo!

Si desea mantener todo GM, un motor 3800 sobrealimentado requeriría algo de trabajo pero encajaría.


Pero tu pregunta es para otro hilo. Este hilo es para hablar sobre diferentes motores GM v8.


Si esto te parece una tontería, gracias al Traductor de Google.

Thank you Google Translate


fidelity101 UberDork
9/6/22 1:42 p.m.

sloppy mechanics would argue against avoid the 4800 series. 

classicJackets (FS)
classicJackets (FS) SuperDork
9/6/22 2:41 p.m.

For the folks who have really done it - how bad is the 1998 LS1 to swap? I see there are kits out there to convert to later PCM for relatively cheap, but it sounds like the remainder of the electrical has other cocnerns too if you were to swap to a later year engine.

I have a 1998 LS1/T56 that would love to swap into something else, and i have access to an LQ9. I would need car accessories regardless.. Would be great to swap the LS1 in, and swap it out for the LQ9 down the road - but hesitant to start if it would require a complete rewire down the road anyway.


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