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Discussion Starter #1
Are they all the same? Looking at all the mentioned heads, it looks like they all have about the same casting and all use the same exhaust bolt pattern.. like 2.75" diagonally? With just slightly different ports, some square, some D shaped, round, etc.

If so, are all the exhaust ports the same height relative to the deck surface? or are some bolt patterns higher or lower?

thank you
 

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I know the first A3's had two different patterns, not 100% sure on the others. Dan Jones has a lot of info and George Klass may be able to help, he makes headers.
 

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The bolt holes are usually / probably in the same location. Having the port location in the same position referenced to said bolt holes unfortunately is not. Not to mention the physical size of the port. Bigger header tubes may get you matched up to a couple / few versions.
 

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Discussion Starter #4
The bolt holes are usually / probably in the same location. Having the port location in the same position referenced to said bolt holes unfortunately is not. Not to mention the physical size of the port. Bigger header tubes may get you matched up to a couple / few versions.
thanks for the post, my thoughts were right in line with exactly what you said.
 

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The early heads A3 had 2.77 inch center to center, there after changed to 2.94 inch, after that. not sure about about d3 stuff.
 
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