What's the Right Size for SBC Crank Bolts?

Maintenance and Repairs
1

I’m in the middle of a rebuild on my small block Chevrolet engine and I need to know the correct crank bolt size for the SBC. I’ve seen lots of conflicting information online, ranging from 7/16" to 1/2". I’m particularly working on a 350 block and want to make sure I’m using the right size to avoid any issues down the line.

Here’s what I’ve gathered so far:

  • General Information:

    • The crank bolt size can vary depending on the specific engine and whether it’s a stock or aftermarket setup.
    • It’s essential to have the correct size not just for fitting but also for ensuring proper torque specifications.

  • Specific Sizes:

    • Most SBC engines traditionally use a 7/16" bolt.
    • Some applications may require a different size, especially if you’re using aftermarket components or a different harmonic balancer.

Questions I have:

  • Torque Specs: What’s the proper torque spec for these bolts? I’ve heard different numbers, and I want to be sure I’m doing it correctly.
  • Aftermarket Parts: If I’ve swapped my harmonic balancer or other components, do I need to use a different bolt size?
  • Recommendations: Can anyone recommend a good source for quality crank bolts for my rebuild?

Any help would be greatly appreciated! Thanks in advance for sharing your knowledge.

3 Likes
2

When it comes to SBC crank bolts, the standard size is usually 7/16"-20 for most applications. However, there are variations depending on the specific engine model and year.

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3

That’s really helpful! I’ve heard there are some differences with older models. Can anyone confirm that?

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4

Older small block Chevys, particularly the pre-1970s ones, sometimes used 3/8"-16 bolts. It’s essential to check your engine’s specifics before buying replacements!

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5

Great, thanks for clarifying. What about torque specifications? How tight should these bolts be?

6

For SBC crank bolts, the typical torque spec is around 70-75 ft-lbs, but always verify with your service manual. Too tight can lead to breakage!

2 Likes
7

Wow, I didn’t realize how crucial proper torque is! Bolts definitely aren’t just ‘tight enough’ in an engine. Thanks for the insight, everyone!

8

Is there a specific tool you recommend for achieving accurate torque?

9

A torque wrench is a must! Investing in a good quality one can save you a lot of headaches later on. Digital ones can be pretty accurate too.

10

I might actually have to upgrade mine; it’s pretty old and might not be very reliable!

11

Don’t forget about thread locker! Using it on your crank bolts can prevent them from loosening over time. Just a friendly reminder!

12

That’s a good tip! Do you all use the same type of thread locker for all bolt sizes?

13

Typically, a blue thread locker is a good choice for crank bolts, as it’s removable but adds enough grip to keep things secure. Just don’t go heavy on it!

14

When selecting crank bolts for an SBC, always check the application specifics. The original bolts are often fine for stock setups, but if you have aftermarket components, you might need stronger bolts. Pay attention to the size and thread pitch.

15

Good point! Also, remember to follow OEM torque specifications. Over-torquing can lead to premature failure. Always refer to the service manual!

16

I agree with vincentburch! Using incorrect bolt sizes can lead to severe damage. Make sure you’re using the right length and grade for your application.

17

Don’t forget about aftermarket options! Many performance cranksets require specific crank bolt sizes. Always check the manufacturer’s recommendations before buying.

4 Likes
18

Right! And if you’re unsure, consulting with a performance shop could save you a lot of headaches down the road.

7 Likes
19

Torque specs vary by application, so double-check what you need. Some folks skip this and ruin their setup. Not cool.

20

It seems like everyone is reviewing crank bolts now! Any thoughts on using ARP bolts? I’ve heard mixed things about them.