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Video: How to Choose the Right Cylinder Heads for Your GM LS Engine

There are two important factors to consider when searching for a set of cylinder heads for an LS engine. The first consideration is the type of intake manifold port; the second is piston bore size of the engine block.

First, let’s talk about the types of GM LS intake port designs. General Motors has three different designs for the LS engine: cathedral port, rectangular port, and raised rectangle port. The cathedral port is the most popular and can be found on the LS1, LS2, LS6, the Vortec 4.8L, 5.3L, LQ4, and LQ9 engines. The raised rectangle intake port design can be found on the LS7 and LSX engines. Finally, the rectangular intake port design is on the LS3, L92, L99, L76, and LY6 engines.

More information on LS Intake Manifolds can be found here.

Now on to the second part–the piston bore size of the engine block. GM made quite a wide range of engine blocks with various piston bore sizes to account for different displacement size engines. The 3.89-inch bore LS1 and LS6 engines can only use cylinder heads designed for a LS1, LS6, or LS2 engine. The reason is the valves will come in contact with the sides of the piston walls if a cylinder head for a larger bore engine is used. The LS2 and LQ9 engine block has a 4.00-inch bore and will accept LS1, LS6, LS2, and LQ9 cylinder heads, as well as cylinder heads from the L92, LS9, and LS3. The 6.2L engines have a 4.065-inch bore size and can accept all of the smaller production style cylinder heads. Finally, if you have gotten your hands on a LS7 or have decided to work with a LSX engine block, those have an even larger bore size and you should work with your engine builder to find the right set of heads for your project.

The chart below provides a quick outline of LS engine/cylinder head compatibility.

There are a few engine blocks that we haven’t mentioned, most notably the LS 5.7L, 5.3L and 4.8L iron block Vortec engines. The 4.8L and 5.3L engine blocks have a 3.78-inch bore and require cylinder heads designed for the smaller bore size. Thankfully, companies like Trick Flow Specialties have stepped up and produced heads for these engines. Trick Flow, for example, has designed its GenX Cylinder Heads for the GM LS 4.8L, 5.3L, and 5.7L Vortec engines.

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  1. Are 317 stk cly heads for a LQ9 engine

  2. Larry Phillips says:

    I have a 1999 ls2 iron engine. What aluminum heads will work with this engine?

    • OnAllCylinders says:

      To find a set that works well, we’ll need lots more info such as use of vehicle, cam, intake, exhaust, transmission type & converter, gear ratio, tire size, and type of vehicle. Call the Summit tech line at 330-630-0240 and they’ll be able to find the right heads.

  3. Keith Covey says:

    My 2004 Factory Stock Chevy Silverado Z71 is loosing engine coolant with no visible signs of a leak. This truck has a 5.3 L engine with less than 90k miles on it. I fear the the heads are cracked at the mounting holes, typical problem for this engine. what would be a good head upgrade for this stock engine? I would like more torque and better fuel milage.

  4. Christopher Luna says:

    im looking to turbocharge my 5.3L and wanting to know the cylinder head cc ratio to boost

  5. Joseph. Havens says:

    I was thinking.of changing heads. On. 5.3l. Motor to. 350 heads. Will. It. Work?

  6. So I’m not dong a swap but I have built a 408 bottom end for a Gen3 LS engine. I have a set of 317 heads and a set of 706 heads. I know that the 317 are known for being the worst GM cast heads, but I don’t think the 706’s will give the flow I want/need. I’m thinking of upgrading to the 823 rec port heads and am wondering the difficulty of the electrical hook ups and connections of a newer intake (factory of course)and how hard it would be to connect to an 06 Silverado stock harness.

    Any insight would be appreciated.

  7. Looking to build a LS4 5.3 from a Chevy Impala ss front wheel drive 2005 – 2009 for an 88 pontiac fiero swap. I need to know what Twisted Flow cylinder heads will work on this?

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