Port Spacing & Templates

Why are exhaust port templates sometimes required?

At Stahl Headers, our two primary goals are quality and performance.  This often requires taking extra steps in order to achieve the best possible results from your new Stahl Header.  Exhaust Port / Header Flange mismatch is one of the quickest ways to rob horsepower.  Therefore, we take port alignment very seriously.

To demonstrate this, a dyno test was conducted using two identical style headers on a Chevy small block engine with spread port cylinder heads.  One header had standard Chevy small block 23 flanges, the other spread port Chevy small block flanges.  The end result was a loss of more than 40 horsepower due to the incorrect port alignment.

This example represents the center two exhaust ports of a standard Chevy 23 small block cylinder head.

As you can see from the overlay, there is a severe mismatch of the port alignment between the standard exhaust ports and the spread port flange.  Another consideration is that each manufacturer often produces their own unique port shapes.  Raised port cylinder heads, ported cylinder heads and other factors can also result in improper port alignment.  Therefore, choosing the correct flange is critical.

By taking the additional step of asking you to provide us with an accurate port template, we remove any uncertainty as to whether we are choosing the proper flanges for your application. 

It is this attention to detail that results in the superior level of performance and quality for which Stahl Headers has been known for over 40 years.  

How to create a proper port template: 

Customers often tell us that their gaskets are a perfect match to their cylinder heads.  We have yet to find this to be true.  It is critical that we have an accurate representation of the location of both the exhaust ports and the bolt pattern.  Faxed templates are not acceptable as this process will distort them.  Mailing us a hard copy is the preferred method.  Therefore, we ask you to please follow the following guidelines when preparing your port template.

Paper works best.  We have found that manila file folders make an excellent choice.  Anything heavier than this is not recommended.  Cardboard, heavy poster board, etc., will not punch out as cleanly, is more difficult to work with, and will not give the desired result.

Position the paper over the cylinder head, making sure that all ports and bolt holes are covered.  (If you are using a file folder you will need to turn it on an angle to cover all the ports and bolt holes.)  Once you have your material in place, use tape to secure it to the cylinder head. (fig.1)
Using a small ball peen hammer, carefully tap around the first bolt hole until the paper has been punched out (see insets in fig.2). 

Insert a header bolt and snug it down enough to securely hold your template in place (fig.2). 

Repeat this process for all of the remaining header bolts (fig.3).
Once all bolts are in place, carefully tap around the edges of each of the exhaust ports until the paper has been cleanly punched out (fig.4).
After you have completed your template, be sure to write on the outside of the template as to the top and/or bottom.  You should also indicate the type of cylinder head the template was made from, as well as your name and contact info.  For mailing purposes you can trim away the excess paper (fig.5).

Mail the completed template to: 
Stahl Headers, 1515 Mt. Rose Ave., York, PA 17403.

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