Do I Have 18mm or 20mm Heads?! - 6.0 Powerstroke (2003-2007)

TLDR:	18mm	20mm
Freeze Plug Diameter	29mm	32mm
Injector Hold Down	T40	T45

There have tons of ways mentioned online about identifying cylinder head dowel size for the 6.0 Powerstroke. Circle vs Square dipstick, engine sticker year or color, truck manufacture date, VIN Number debates, and more. Unfortunately none of those things are a sure fire way to tell which cylinder heads you have! 

The common rule of thumb we have seen is that 2003-2004.5 trucks have 18mm heads, 2005-2006 model year trucks can be either 18mm or 20mm, and 2007 model year trucks have 20mm heads. Most E-Series vans follow the same year splits expect they continued to use the commonized 20mm cylinder heads from 2008-2010 when their production ended. However, it isn't always as simple as that! In this article we are going to go over the best ways to tell which cylinder heads your truck has.

If you aren't sure what size cylinder heads you have on your truck, there are two ways to know for sure!

Check #1 - Cylinder Head Freeze Plug Hole Diameter Measuring Procedure:

This should be the first thing you check. Step 1 before ordering new cylinder heads for your 6.0 Powerstroke. Usually, this first measurement is enough to determine what size heads you will need. It is as simple as a cheap cup of Play-Doh. Run to your local store or buy some online and stuff it into the freeze plug holes located on the side of your head. When you pull the clay back out of the freeze plug hole be careful not to distort it before measuring.

Note: You are measuring the larger circle impression on the clay. We are trying to determine the diameter of the freeze plug HOLES on the side of the cylinder head NOT the ID of the freeze plug itself. Watch the video below to see this in better detail! 

Check your cylinder head size is as easy as follows: 

Note: The freeze plug holes measure as follows.

• 18mm heads = 28mm freeze plug holes 
• 20mm heads = 32mm freeze plug holes

One Last Catch...

If your engine or cylinder heads were replaced after MY2008 model year with "Commonized" or "Service Replacement" cylinder heads due to cracking leading to diesel in the coolant at a dealership, there is a possibility that they will feature the larger 20mm style freeze plugs, but still be an 18mm head. If you think this may be the case for your truck, such as if you have a 32mm freeze plug hole on an early 2003 truck, read this section!

Check #2 - Injector Hold Down Hardware:

The Only 100% Accurate Way To Know 18mm vs 20mm!

One final check before ordering your heads is to pull the coolant reservoir, FICM, and remove the driver side valve cover to gain view of the injector hold clamps. This is the final check to know, for sure, which style of cylinder heads your 6.0 Powerstroke needs. 

Note: The hold down clamps measure as follows.

• 18mm heads feature a T40 injector hold down bolt.
• 20mm heads feature a T45 injector hold down bolt.

In Conclusion...

There are more than a few ways to attempt to find out which cylinder head dowel size you have on your engine, but we laid out the two most reliable ways we have found to help make this determination easier for you! If you have any questions please call us or when you are ready to buy new heads for your truck check out our collection HERE!