September 30, 2020

LS Cylinder Head Install Procedure

So you got a new set of heads or for some reason you need just reinstall the ones on your engine? It’s really a fairly simple task, but there are a few key steps and things to know. And a few tools you must have. Read on for details to make sure you do it right.

Never reuse LS head bolts

LS head bolts are torque-to-yield (TTY), meaning they cannot be reused a second time. A TTY bolt is stretched when fastened, typically with a specified degree of turn after torquing. This means the bolt will not go back to its original shape after being installed.

Make sure you purchase a high quality new set of head bolts and only use them once. They’re not that expensive.

Before you start

We’ve talked fresh bolts – the most important piece. Now let’s make sure that you have the tools you need:

  1. Torque wrench that can do 22 ft-lbs / 264 in-lbs. Sometimes the big wrench is too big and the small wrench too small. Check before you start.
  2. Torque angle gauge. Not everyone has this and it’s a must-have for this install. It will allow you turn the bolts the exact number of degrees required. Do not guess this. Get a torque angle gauge. Most hardware stores and any home improvement store will have one.
  3. Metric socket set and extensions.
  4. Optional: breaker bar. This is like a ratchet for sockets except it doesn’t ratchet.

Also make sure the block is properly secured on the stand or wherever it is. You will be using quite a bit of force.

Installation procedure

  1. There are two dowel pins on each side of the block (or you need to press them in). They are used to align the gasket and head to the block. Grab one of the old M8 bolts too.
  2. Thoroughly clean the deck surface of the block and the head with a clean rag and cleaner like acetone.
  3. Put the head gasket on the block, ensuring that any markings for “front” or “this side up” are in the correct place – i.e. at the front and/or you can read it.
  4. Place the cylinder head on top of the head gasket, matching the dowel pins. It should sit on there easily and securely, but we like to just thread one of the small M8 bolts into the top center hole. Just a few mm in is fine.
  5. Take all the new bolts and install them finger tight.
  6. First pass of torquing the M11 bolts (#1-10): spec is 22 ft-lbs for all engines and bolt sizes. Make sure to follow the sequence in the graph below.
  7. Second pass of torquing the M11 bolts (#1-10): 90 degrees. This is where the torque angle gauge comes out. If you haven’t used one before, practice with it a bit. We also recommend using a breaker bar and not a ratchet for this step. Try to use as short of an extension on the socket head as possible and don’t use a warble extension.
  8. Third pass of torquing the M11 bolts (#1-10): round the head you go again. This time an additional number of degrees that varies by engine. This is going to require some good strength and leverage:
    • Gen III (LS3, LS6, etc.) M11 x 155.5 mm bolts: 90 degrees
    • Gen III (LS3, LS6, etc.) M11 x 110 mm bolts: 50 degrees
    • Gen IV (LS2, LS3, etc.) M11 x 155.5 mm bolts: 70 degrees
    • For engines using M12 bolts, refer to the GM service manual
  9. Lastly, torque the M8 bolts (#11-15) in 1 pass to 22 ft-lbs. This is going to feel like a piece of cake after the previous steps.

Bolt sequence

And that’s it! Now you’ll want to install the rocker arm bar, pop the push rods in and install the rockers. This also requires a proper procedure, which we’ll explain soon.

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