What is the LS Crank Bolt Size?

Technical Discussions
1

I’m in the middle of prepping for an LS engine rebuild, and I’m trying to make sure I have all the right specs before I start disassembly. One critical question I have is: what is the exact size of the crank bolt for the LS engines?

A Few Details:

  • Engine Type: Gen III/IV Chevy small block V8
  • Bolt Specifications: I want to ensure I get the right size and thread pitch for compatibility with the crankshaft and any aftermarket components I might want to use.

Why It Matters:

When reassembling an engine, using the correct bolt size is crucial for ensuring that everything fits securely and operates properly. I’ve read that using the wrong size can lead to serious issues, especially during high-performance applications.

Questions:

  • Can anyone confirm the size for me?
  • Are there any aftermarket options you’d recommend that might have different sizes?
  • What torque specs should I be aware of when tightening the crank bolt?

I appreciate any insights or guidance on this topic. It’ll really help me keep things running smoothly!

8 Likes
2

I’ve been digging into this myself. The standard crank bolt size for LS engines is typically 7/16-20 with a length around 3.0 inches. You can find this in the OEM service manuals.

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3

That’s super helpful! Is there a specific manual you recommend for LS specs?

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4

You can check the GM Service Manual for the LS series engines. They usually have detailed specifications for bolt sizes and torque settings.

5

I’ve seen variations, though. Some aftermarkets offer different lengths. Are those safe to use?

6

Great! So, GM manuals are the gold standard for these specs? I’ll have to find one!

3 Likes
7

Yes, GM documentation is very reliable. However, make sure to double-check length and thread pitch before making any purchases.

8

For those who like forums, places like LS1Tech have threads dedicated to such specifics, where users share their experiences with different sizes.

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9

I’ve spent hours on that forum. It’s one of the best for LS engine info!

10

Just be careful with bolt sizes. Using the wrong size can lead to serious engine problems. I’ve learned the hard way!

11

That is a great point, and I definitely want to avoid any mistakes. Better safe than sorry!

1 Like
12

Has anyone tried non-OEM crank bolts? I’m curious about their performance and reliability.

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13

I once used aftermarket bolts, and it was a disaster! Stick with OEM for peace of mind.

14

That’s a bit scary! I’ll definitely heed the warnings about aftermarket parts.

15

On a lighter note, at least if things go wrong, we’ll get some awesome stories, right? LOL.

16

The LS crank bolt is typically a 1-1/4" bolt. For safely removing and installing it, you’ll need a good impact wrench or a breaker bar with a socket that fits snugly. Don’t forget to check the torque specs which usually range around 74 lb-ft to 80 lb-ft depending on the year and model.

17

That’s good to know! Do you have any tips for ensuring I don’t strip the bolt head while I’m loosening it?

18

Use a high-quality socket, and make sure it’s fully seated on the bolt before applying torque. Also, consider using a torque wrench to avoid overtightening when reinstalling it. A little anti-seize on the threads can help, too!

19

Great advice! Is anti-seize recommended for every installation?

20

Yes, but use it sparingly. It can affect the torque readings, so be sure to adjust your torque value slightly if you do it. Always check your manuals for specific guidelines.