What is this for??!


New Member
Jul 28, 2003
Houston, Tx
I pulled the heads off of my '66 289 to replace the vavle springs and seals and I noticed that each of the exhaust ports has a small hex head screw at the top left hand corner that goes into exhaust port.

I have looked at the 3 -4 Ford small block books that I have and have not found any pictures or references to these.

Any idea what they are for??

if it matters, the casting number on the heads is C6OE-M

outside angle

inside angle
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302 coupe

Founding Member
Mar 2, 2000
Macon, Ga.
those are plugs for the thermactor holes. Basically, those heads were originally equipped with an air injector tube for smog reduction, but it has been deleted and the holes plugged with the hex head plugs.


New Member
Apr 4, 2004
Houston Texas
Yep, 302 coupe nailed it....those are thermactor ports that have been blocked off. Those are California emission heads from 1966. Sell them to someone out in the whacky state that needs original equipment to pass smog or just use them because they really are no different from normal 66 289 heads except for the holes.

BTW.....resize the pics a little smaller next time....