LS Head Bolt Torque: Precision Specs for Engine Performance

The cylinder head gasket is one of the most over-engineered and stressed components in an internal combustion engine. That’s why even the laziest mechanics or DIYers never ever skip tightening the cylinder head bolts to the exact torque specified by the manufacturer and in the exact sequence. And needless to say, you shouldn’t either. 

The LS head bolt torque for the third generation (LS1 and LS6) starts with bolts 1 to 10 and is 22 ft-lb for the first pass, 90° for the second pass, 90° for bolts 1 to 5, and 50° for bolts 6 to 10 for the third pass, and 22 ft-lb for bolts 11 to 15 for the final pass. The head bolt torque for the fourth generation (LS2, LS3, LS4, LS7, LS9, LSA) starts with bolts 1-10 and is 22 ft-lb for the first pass, 90° for the second pass, 70° for the third pass, and then 22 ft-lb for bolts 11-15 as the final pass.

LS Head Bolt Torque Explained

The LS head bolt torque is pretty complicated. First of all, the head bolts for all LS engines are TTY (torque to yield) which means they cannot be reused once they are tightened to the correct torque specs. Such bolts stretch out too much after the initial tightening that they become too long and fragile to reach such high torque again and will most likely snap. 

Next, all LS cylinder heads have a tightening sequence which is just as important as bolt torque. Tightening the bolts in the correct sequence ensures the clamping force is distributed equally and that the cylinder head gasket doesn’t leak.

Furthermore, multiple passes mean you need to tighten the correct bolts in the right sequence to a specific torque, then repeat the process again with a different torque as many times as there are passes.

Now, the LS head torque specs ft lbs are easy to understand, but the LS cylinder head bolt torque is also expressed in degrees for the second and third passes. For example, if the torque spec says 90°, it means you need to turn the bolt clockwise 90° degrees or a quarter of a turn. But to do that precisely, you need a degree torque wrench or a degree dial for a standard wrench.

LS Head Bolt Torque Sequence

Here we will draw out the LS head bolt torque pattern with numbers. Each number represents a bolt, and number 1 means it’s the first bolt to tighten, number 2 is the second one,  and so on. But keep in mind that bolts 11-15 are only tightened on the fourth pass after you tighten all other bolts to the correct and final specification.

LS Cylinder Head Install Procedure

The LS cylinder head install procedure is pretty simple, apart from the complicated bolt-tightening sequence and torque specs. Before you install anything, make sure the engine block mating surface is clean, and also wipe it down one last time before placing the head gasket on it.

Next, install the alignment pins if your engine block has them, and install the head gasket. Make sure you double-check the head gasket orientation because often, one side must be facing upward, but you will find the orientation written on the gasket itself.

After that, wipe down the cylinder head mating surface and put two bolts into its bolt holes so you can align it with the engine block easier. Next, mount the cylinder head onto the engine block and torque it down in the correct sequence and the correct bolt torque. And once again, make sure you have brand new cylinder head bolts.

Lastly, you can have a look at this video, where the whole cylinder head install procedure for LS1 and LS6 engines are demonstrated and explained. The procedure is the same for other LS engines, with the only difference being bolt torque specs.

What Are the Torque Specs for LS Head Bolts

By now, you already know how complex the Chevy LS head bolt torque specs are. But if nothing, the torque specs for all third gen engines are the same, and while the Gen 4 ls head bolt torque is different than Gen 3, it’s still the same for all engines of its generation.

Still, there are some things you should not miss, so before you jump into all the torque specs, read the part that applies to each generation individually.

Third Generation LS Cylinder Head Torque Specs (1997-2005)

The third generation Chevy small block was only available with two Ls variations, the LS1 and LS6. And while the cylinder head torque specs are the same for both, there is one thing we need to turn your attention to just in case you miss it.

And that’s the third pass where you should turn bolts 1, 2, 3, 4, and 5 by 90° for the final pass and bolts 6, 7, 8, 9, and 10 by 50°. But mind you, the bolts are mixed up between the center ones and the exhaust side ones, so make sure you have a diagram in front of you before you start.

LS1 Cylinder Head Bolt Torque Specs

Bolts 1-10 to 22 ft-lb

Bolts 1-10 turn 90°

Bolts 1-5  turn 90°/ Bolts 6-10 turn 50°

Bolts 11-15 to 22 ft-lb

Vehicles With the LS1 Engine

LS6 Cylinder Head Bolt Torque Specs

Bolts 1-10 to 22 ft-lb

Bolts 1-10 turn 90°

Bolts 1-5  turn 90°/ Bolts 6-10 turn 50°

Bolts 11-15 to 22 ft-lb

Vehicles With the LS6 Engine

Fourth Generation LS Cylinder Head Torque Specs (2005-2020)

Although the fourth generation LS saw six different variations of the engine ranging from 5.3 to 7.0 liters, from naturally aspirated to supercharged, and from longitudinal to transverse, the head bolt torque is the same for all. Plus, the tightening sequence and passes are much simpler than with the third-gen.

LS2 Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LS2 Engine

LS3 Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LS3 Engine

LS4 Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LS4 Engine

LS7 Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LS7 Engine

LS9 Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LS9 Engine

LSA Cylinder Head Bolt Torque Specs

Bolts 1-10 (22 ft-lb)

Bolts 1-10 (Turn 90°)

Bolts 1-10 (Turn 70°)

Bolts 11-15 (22 ft-lb)

Vehicles With the LSA Engine

FAQs:

Can you reuse head bolts on LS engines?

No, you cannot reuse head bolts on LS engines because they are TTY bolts (torque to yield). A torque-to-yield bolt means it stretches when it’s tightened, and after you remove the bolt, it doesn’t return to the original length, which means it loses its strength.

Can you over-torque head bolts?

Yes, you can over-torque head bolts. Head bolts can snap just like any other bolt if it’s over-torqued, and if your engine block is aluminum, the threads can strip, resulting in a major repair job if you want to save it.

Is it ok to reuse head bolts?

Whether or not it’s ok to reuse head bolts depends on the type of engine and bolts. If your engine requires TTY (torque to yield) bolts, then they cannot be reused. However, most engines use normal, reusable bolts.

Do I need to retorque the head bolts?

Whether or not you need to retorque the head bolts depends on the tightening sequence and bolt torque on your specific engines. Some head bolts require multiple passes with different torque settings, which in other words, means they need to be retorqued. But that’s not the case for all engines.

What happens if you don’t torque head bolts?

If you don’t torque the head bolts enough, the head gasket will most likely leak, and the cylinder head can warp because of excess flexing. On the other hand, if you over-tighten the head bolts, they can snap or strip the engine block threads.

Are LS and LT heads interchangeable?

No, LS and LT heads are not interchangeable from the factory. LT cylinder heads have direct fuel injection, variable valve timing, and cylinder deactivation. That said, the coolant passages line up, and an LT head will fit on an LS engine with some modifications.

Final Words

Ultimately, the LS head bolt torque specs are pretty difficult to explain without a proper demonstration. Still, we can say that the third-gen LS engines (LS1 and LS6) are 22 ft-lb for the first pass (bolts 1-10), 90° for the second pass (bolts 1-10), 90° for the third pass (bolts 1-5), and 50° (bolts 6-10). And for the fourth pass, you tighten the bolts 11-15 to 22 lb-ft.

On the fourth-gen engines (LS2, LS3, LS4, LS7, LS9, and LSA), the first pass is 22 ft-lb (bolts 1-10), the second pass is 90° (bolts 1-10), and 70° for the third pass (bolts 1-10). And for the final pass, tighten bolts 11-15 to 22 ft-lb. Also, make sure you check out the tightening sequence found earlier in this article.