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Unknown Threaded Hole in Head
https://www.slantsix.org/forum/viewtopic.php?t=68700		 Page 1 of 1
Author:  morsim [ Sun Jul 12, 2026 11:58 pm ]
Post subject:  Unknown Threaded Hole in Head
What could this hole be for? It's been found on a newly installed '74 head. Does not exist in my older '69 head.
When filling my rad, coolant started dispensing out of it and into the lifter galley :o
It's threaded, and I plugged it with a small screw + teflon tape...
Any ideas?

Image
Author:  Dart270 [ Mon Jul 13, 2026 2:19 am ]
Post subject:  Re: Unknown Threaded Hole in Head
Oh, I'm sorry! I drilled and tapped that hole in about 2004 to mount part of an EFI fuel rail and forgot it was there and that you needed to plug it. At least it was an easy fix.

Lou
Author:  morsim [ Mon Jul 13, 2026 9:36 am ]
Post subject:  Re: Unknown Threaded Hole in Head
Quote:
Oh, I'm sorry! I drilled and tapped that hole in about 2004 to mount part of an EFI fuel rail and forgot it was there and that you needed to plug it. At least it was an easy fix.

Lou
No worries! :D
Author:  Rick Covalt [ Mon Jul 13, 2026 1:42 pm ]
Post subject:  Re: Unknown Threaded Hole in Head
That is a top secret nitrous injection port. Lou is very sneeky!! :D :D
Author:  Reed [ Mon Jul 13, 2026 11:43 pm ]
Post subject:  Re: Unknown Threaded Hole in Head
Custom bleed valve for purging air out of the cooling system. :wink: 8)
Author:  Dart270 [ Tue Jul 14, 2026 9:27 am ]
Post subject:  Re: Unknown Threaded Hole in Head
Yes, it also is a perfect location for cooling system bleeding, although I've almost never had trouble with that...

Lou
Author:  volaredon [ Tue Jul 14, 2026 3:46 pm ]
Post subject:  Re: Unknown Threaded Hole in Head
That is a machined boss for something. I've seen various sensors mounted there on newer ones. Mostly ones that originally had lean burn ignition.
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