Large hole on back of valley cover

BigTallKen

BigTallKen

Member
I have a large hole on the back of my 304 intake valley cover.

It looks like it May be threaded for something..

Oil pressure sender? Vacuum port? Pcv?

Any ideas?

I have a 304 with a 2v carb on the stock intake manifold.
 
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If you are talikin' the sheet metal cover under the intake manifold, located on the "sloping" portion, then that is where the pcv "grommet" pushs into position. Very common, failure-prone item.

We got new ones here at ihon. You will also need a pcv valve to go with it if ya don't already have one.

If...you mean a hole actually in the intake manifold itself, then that could be many different things. We'd need a pic of what yours looks like to make that determination. There were quite a few variations in intake manifolds for these engines over the years.
 
I will take a picture later today.

I do believe that there is a pcv valve on my engine in the drivers side valve cover, but I'll have to look and be sure.
 
Pics will tell the story, needs pic of the valve cover plumbing also.

There were many variations on pcv plumbing on these engines, depending upon production era and platform they were installed in.

Indeed...some had a "cleanable" pcv installed in one valve cover, but usually that valve was installed into the vacuum "tree on the intake manifold.

There were also "throwaway" pcv valves that screwed in instead of pushing into a grommet.

What you May think is a pcv valve is actually a "flame arrestor" mounted to the valve cover, that was part of the arrangement on the "closed" pcv systems that came into production around '67.

However, I've seen one engine in recent memory that had a pcv valve screwed into each valve cover, those were connected together with a hose! And yes, that motor was blowing oil out of every gasket and seal and had been run that way obviously for years.

Because the majority of these engines have had all kinds of po crap done to 'em over the years, there is no telling what ya might find. It's always a treat to find a virgin IH setup under any hood!
 
Ok, here's the pic.

I hope this helps.

There is one pcv valve on the drivers side valve cover. This hole is simply empty.

It is a 304 with a manual transmission.
 

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Yep ken, that's a pcv location. I have the same on the 392 in hooty. The 345 that was in it before did not have that valley location. That engine had the threaded version on the driver side valve cover.
 
Nice pic! Trev discovered the same kinda swap around parts deal on hois motor!

There is a baffle spot welded to the underside of that valley cover, that grommet leads into the baffled chamber and must have a "throwaway"-type pcv in it. That is the "last gen" pcv system that lasted through the end of production of these engines around 1984 or so.

If the valve covers on your motor are oem to that item, then what you are discussing is not a pcv, it's a flame arrestor dude! Take it out and clean it, you'll see it's full of grunge which is hiding the frog hair inside. Soak in solvent and blow out several times to clean.

Then install the correct pcv in the grommet, the hose goes to the base of the carb where the the whitetrash "plug" is stuck in.
 
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