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On a 400 - What do you call that little soft plug in the front of the head, into the exhaust/EGR system, and anybody remember what size it is? I've changed them before, but it's been too long. My parts guy looks at me like I'm drooling on myself.......
I will get a picture - it's a tiny little soft plug (maybe 1/2"?) right in the front of the head, more/less behind the alternator, that goes into the exhaust. I was told once that it was into the EGR rail/cavity inside the head, but I really don't know for sure, never looked that close at the head. It seems like I had a "universal" soft plug bubble-pack from the parts store that had one close enough on the last one I changed, but, of course, nobody in town had a kit like that this time around, so I was hoping to just get the one I need and be done. Will do a little more research, though......
I would think at one point they would have had "emissions" heads like the small block did. On the 302, the 80's stuff had a crossover tube behind both heads, which i threaded the holes and blocked them off with a large bolt (cut short). The fronts of the heads have a threaded insert that blocks the hole and allows you to mount things. I can only imagine this situation is similar?
That's exactly what this one looks like, it should be a mounting hole - the matching boss on the driver's side head is where the upper bolt for the power steering pump bracket bolts. It would seem like this one would be threaded, too, but it just has a soft plug in it - never looked deeper in the hole, maybe it's threaded deeper inside? That would be the logical fix, a capscrew - I will be next to it tonight, will investigate a little further.
As far as what the hole goes into - I don't know if it's actually EGR-related or not. I did read somewhere last night that 335 motors were designed for an air-injection system, and rather than an external pipe with threaded-into-the-manifold fittings like a Chevy, it was cast straight into the head. Since 400's first came out in cars, I believe (?), this would make some sense that it was designed for a little stricter standards than a 3/4 ton pickup, so this could actually be a capped off, unused air injection manifold?
Have an air pump on my F350. Got to go without cats due to the 8550 GVWR, but still had most of the other stuff.
Paul
Is yours a Cali pickup? Can't say that I've ever seen one up here (MT) this vintage with an air pump, just EGR - 150's either. Where does it plumb in, this hole?
The hole measures just about exactly 1/2" with a cheap caliper and not quite getting a square shot since I didn't pull the alternator off yet (still driving it), so I'd imagine it'll end up being a 33/64" - have one coming, will let you know if it fits!!
based on your picture of "the hole" it looks just like the type on my 302, as mentioned. There is a insert in there where the piece is threaded both internally and externally. You might have a hell of a time extracting that, but you could definitely thread in a bolt with some pipe dope on the threads to seal it off. It is a cavity that travels all the way thru the head, tied into the exhaust ports. If you look at the same area on the rear of it you should have a hole in the same location.
and anybody remember what size it is? 
