What is this port?

I cannot believe all the times I have been under the hood I never wondered what this was. Right now there is a 7/16" hose attached to it and plugged with a bolt. Chiltons, Haynes and BL all show pics of cylinder heads but none of them have this port. I have not unplugged the hose to see what comes out if anything.

I welcome any input...

It's the hot water inlet that originally ran from the water choke of you ZS carb.

Really.


In to the carbs... where did the outlet from the carbs go?

Outlet from the carb was T'd in to the hard line which goes from the lower radiator hose to the outlet of the heater core.

Michael,
Your original ZS carb had a hot water choke on it. There would have been a hose from your lower radiator hose to the choke on your carb and a hose from the choke back to the engine via that fitting on the rear of the head. If your car has had the ZS carb removed or a manual choke installed that's why that fitting is plugged. I, like others, have removed that barb and replaced it with a home made solid plate.

Cheers!!

"Carbs" plural? Have you swapped back to a set of SUs? If so there was/is no provision for heated watrer/chokes on those. The previous incarnation, with the single Stromberg, had a hot water activated fuel enrichment system. The part that you are speaking of is merely the return-to-the-block port for the water that had been inside the choke.

BTW: I see this plugged business often. You are skating on thin ice by stopping up the port like that, as you are only a moment away from that rubber rupturing and having all of your coolant dumped with the resultant overheated and trashed engine.

Better to make a blanking plate and toss that piped outlet.

Jack

On my 76 im going to drill/tap a blanking plate (outlet on back of head) to install a bleed
fitting ,to get rid of any air trapped in rear of head during refills of coolant..

Jack I am webberized.
The manifold has a watewrpassage (unused at present) that I may hook up to the heater core... its on "the list"