Best Sealant for Head Bolts: Top Picks and Expert Tips

In the world of automotive repair and engine assembly, the right sealant for head bolts is a critical choice for ensuring the longevity and performance of an engine.

This article explores the best sealants for head bolts, focusing on their compatibility with engine materials, resistance to high temperatures, and chemical stability.

Whether you’re a seasoned mechanic or a DIY enthusiast, understanding the nuances of different sealants can make a significant difference in your engine’s health and efficiency.

Best Sealant for Head Bolts: Top Picks and Expert Tips

Choosing the Best Sealant for Head Bolts

Material Compatibility

When selecting a sealant, I need to consider the compatibility with the materials in my engine.

Some popular sealants for head bolts are Loctite Pipe Sealant with Teflon and Permatex Form A Gasket No 2 sealant.

Both of these sealants are reported to work well with various metals used in automotive applications.

Temperature Resistance

My engine’s operating temperature is a crucial factor in choosing a sealant. Sealants should withstand high temperature ranges since engines can get quite hot.

For example, the Permatex Form A Gasket No 2 sealant mentioned earlier is known for its excellent temperature resistance.

Chemical Resistance

Lastly, the sealant I choose must have good chemical resistance. Engines consist of various fluids such as coolant, oil, and gasoline, and it’s essential for the sealant to maintain its properties in the presence of these substances.

Both Loctite Pipe Sealant with Teflon and Permatex Form A Gasket No 2 sealant offer this chemical resistance, making them suitable choices for head bolts in my engine.

Steps to Apply Head Bolt Sealant


Before applying the sealant, it’s crucial to inspect and clean the head bolts. Dirty or damaged threads can cause false torque readings and reduce clamping force by up to 50%. To ensure proper application, I follow these steps:

  1. Thoroughly clean threads using a wire brush.
  2. Inspect bolts for any defects, such as nicks or deformations.
  3. Replace damaged bolts with new ones.


Once I’ve cleaned and inspected the bolts, I choose a suitable sealant. Some popular options include LocTite and Permatex #518, which are well-recommended for their effectiveness. Here’s how I apply the sealant:

  1. Apply a thin layer of sealant over the bolt threads, ensuring even coverage.
  2. Hand-tighten bolts, taking care not to over-tighten.

Curing Process

The curing process depends on the specific sealant used, as each product has its own requirements. For instance, Permatex #518 remains plastic and cures when there is no oxygen anaerobic. To ensure optimal results, I:

  1. Follow the manufacturer’s instructions regarding cure time.
  2. Allow the sealant to cure fully before attempting to torque the bolts.
  3. Double-check that the curing process is completed before assembling the engine.

In conclusion, when applying head bolt sealant, I focus on preparing the bolts, selecting an effective sealant, and following the recommended curing process. These steps help ensure a proper seal and optimal engine performance.

Best Sealant for Head Bolts: Top Picks and Expert Tips

Safety Precautions

When working with head bolt sealants, it’s important to prioritize safety. I always make sure to carefully read and follow the manufacturer’s instructions for any product I use.

One common aspect is ensuring proper ventilation. Sealants can emit fumes that may be harmful if inhaled in large amounts or for extended periods. I like to work in a well-ventilated area to minimize any risks.

Additionally, using gloves can be helpful in preventing skin contact with the sealant. I find that some sealants can cause skin irritation or even allergic reactions in some individuals.

An important thing to note is the drying time of the sealant. I carefully check the product label for the recommended drying time and adhere to it. This helps avoid excessive torque or other damage to the head bolts.

Some popular sealants for head bolts are Permatex No. 3 and Permatex 59235 High Temperature Thread Sealant. Here’s a comparison table I made for them:

Permatex No. 3– Slow drying
– Non-hardening
– Resistant to oil, gasoline, and grease
– May not be ideal for very high temperatures
Permatex 59235 High Temperature Thread Sealant– Suitable for high temperatures
– Good for oil PSI sending units and sensors
– May be harder to find in some stores

In conclusion, it’s crucial to prioritize safety when working with head bolt sealants. Using the right precautions ensures a secure and successful installation while minimizing potential risks.

Best Sealant Brands for Head Bolts

In this section, I’ll discuss some of the best sealant brands for head bolts. We’ll delve into three popular options: Permatex, Loctite, and J-B Weld.


Permatex is a widely recognized brand in the automotive industry, known for its reliable adhesives and sealants.

One popular option is Permatex Form A Gasket No 2 sealant. It’s slow-drying, non-hardening, and approved for both aviation and automotive applications.

Best Sealant for Head Bolts: Top Picks and Expert Tips


Loctite offers a variety of thread sealants, and their Pipe Sealant with Teflon is a go-to for many automotive professionals2. This sealant has been used by several OEMs, including Chevrolet, which speaks to its quality and effectiveness.

Here’s a brief comparison table of the two sealants:

Permatex Form A Gasket No 2Slow-drying, non-hardening, versatileRequires precise application
Loctite 1158514Designed specifically for head boltsMight not be as versatile

J-B Weld

J-B Weld is another trusted name in the automotive sector, offering a range of adhesives and sealants. While not as popular as Permatex or Loctite for head bolt applications, some users still prefer J-B Weld products for their high-quality and durable results3.

PermatexSlow-drying formulaNone mentioned
LoctiteOEM-approvedNone mentioned
J-B WeldHigh-quality and durableLess popular

With these options in mind, you can choose the best sealant for your head bolt installation based on your preferences and requirements. Remember, using a reliable sealant can help ensure a proper seal, preventing leaks and ensuring the longevity of your engine.

Common Mistakes When Using Sealant

One common mistake I often see is not cleaning the threads properly. It’s important to thoroughly clean the threads of both the bolt and the hole. Dirt and grime can reduce the sealant’s effectiveness, resulting in leaks later on.

A simple example of a thread sealant is LocTite or Permatex #518, which can even seal dirty or oily parts.

Another issue is using the wrong type of sealant for the application. Different sealants have varying strengths and properties, so it’s crucial to choose the correct one.

Over-applying sealant is also a common mistake. It’s essential to use just enough to create a tight seal but not so much that it can squeeze out and create a mess. Excess sealant can also block oil passages and lead to poor engine performance.

Lastly, not following the manufacturer’s instructions can lead to issues. Some sealants, like ARP moly lube, require specific torque settings for optimal performance. Ignoring these recommendations can result in a weak seal or even bolt damage.

In conclusion, to avoid mistakes when using sealant, make sure to:

  • Clean threads properly
  • Choose the right type of sealant
  • Apply the correct amount of sealant
  • Follow the manufacturer’s instructions
Best Sealant for Head Bolts: Top Picks and Expert Tips

Maintenance Tips

I always ensure proper head bolt maintenance, as it’s essential for my engine’s performance and longevity. Keeping the bolts clean and using the right sealant can make all the difference.

When I clean my head bolt threads, I use a wire brush to remove any dirt or debris. This helps prevent false torque readings and maintains the bolt’s clamping force. It’s crucial to inspect each bolt, and if necessary, replace any that are nicked, deformed, or worn.

Selecting the right thread sealant is vital too. I’ve learned that the Permatex Aviation Form a Gasket and plumbers’ Teflon sealant have earned praise for their effectiveness.

These sealants ensure the correct torque and offer good sealing properties. Some other popular options include:

I believe that comparing different sealants helps me find the most suitable one for my needs. Here’s a comparison table to give you an idea:

SealantTemperature ResistanceTorqueEase of ApplicationRetorquable
Permatex Aviation Form a GasketHighGoodBrush topYes
Plumbers’ Teflon SealantModerateGoodSelf-adheringYes
Permatex High Temperature Thread SealantHighExcellentBrush topYes
Permatex Form A Gasket No 2ModerateGoodBrush topYes

I follow these tips and always stay mindful of thread sealant expiration dates, as well as recheck the torque after a certain mileage, depending on the manufacturer’s recommendations.

By doing so, I keep my engine running smoothly and ensure its longevity.

Longevity and Durability of Sealants

As I explore various head bolt thread sealants, longevity and durability are key characteristics I want in a product.

One popular option is Permatex Form A Gasket No 2 sealant, known for its slow-drying and non-hardening properties. It’s trusted in both automotive and aviation applications.

Another reliable choice is Permatex 59235 High Temperature Thread Sealant, designed for head bolts going into through holes.

It’s resistant to high temperatures and safe to use with various applications, such as oil PSI sending units, sensors, and fuel fittings.

Here’s a comparison table to summarize the main characteristics of each.

Sealant NameKey CharacteristicsApplications
Permatex Form A Gasket No 2 sealantSlow-drying, Non-hardeningAviation & Automotive applications
Permatex 59235 High Temperature SealantHigh-temperature resistant, VersatileHead bolts, Oil PSI sending units, Sensors, Fuel fittings

One example of a brand that uses lube on their head bolts is Cummins, employing moly paste on their products.

This method prevents friction and has proven effective. It’s worth considering other lubricants similar to moly paste for achieving the best results.

When selecting the right sealant, it’s crucial to take note of some important factors. For instance, the material and application requirements of your project, as well as your personal preference, can play a significant role in your decision.

Best Sealant for Head Bolts: Top Picks and Expert Tips

Frequently Asked Questions

What type of sealant is recommended for SBC head bolts?

For Small Block Chevy (SBC) head bolts, many experienced mechanics recommend using Permatex Aviation Form a Gasket. This sealant is re-torqueable and provides a reliable seal.

Is Teflon tape suitable for head bolt sealing?

I wouldn’t recommend using Teflon tape for head bolt sealing. Teflon tape is more appropriate for plumbing applications, while purpose-made sealants like Permatex or ARP Thread Sealant are better suited for automotive use.

Do Fel-Pro head bolts require any sealant?

Fel-Pro head bolts usually come pre-coated with a thread sealer. This means you don’t need to apply any additional sealant unless the manufacturer explicitly states otherwise.

What’s the difference between ARP thread sealant and Permatex?

Both ARP thread sealant and Permatex are excellent choices for head bolt sealing. The main difference between them is the brand. ARP thread sealant is specifically designed for use with ARP bolts, while Permatex is a more common option suitable for various automotive applications.

Should I apply thread sealant on head bolts?

Yes, applying thread sealant on head bolts is essential. It prevents coolant or oil leaks and ensures that head bolts are adequately torqued. Make sure to use a suitable automotive-specific sealant like Permatex or ARP Thread Sealant.

Which sealant is best for head bolts in a water jacket?

For head bolts in a water jacket, I would recommend using either Permatex Aviation Form a Gasket or ARP thread sealant. Both options provide excellent sealing properties and are specifically designed for head bolt sealing in automotive applications.


Selecting the perfect sealant for head bolts is more than just a technical decision; it’s about safeguarding the heart of your vehicle – the engine.

Throughout this article, I have examined various aspects of head bolt sealants, from their material compatibility and temperature resistance to application tips and safety precautions.

By carefully considering these factors and choosing a quality product, you can ensure a durable and reliable seal that stands the test of time and harsh engine environments.

Remember, the right sealant is not just about preventing leaks; it’s an integral part of maintaining your engine’s optimum performance.



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