Manifold EGR Jets

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Professor Fate

Professor Fate

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I have a '79 casting date spread bore manifold that I got in a parts deal a while back, just getting around to using it now.
It already had the EGR jets removed from the plenum floor, leaving just the open threaded holes, so I tried to plug them- tried pipe thread, fine thread, coarse thread, nothing seems to fit. Was this a special thread, and does anybody make plugs for this? Almost ready to just run pipe taps into them, but thought I'd check here first.
 
the one I did in a Super 6 intake was 3/8 NPT. AFTER I dug all the carbon out of the threads!!!!!
 
My brother had a 77 van/360 with missing floorjets; but the EGR was blocked off.
I took the intake off to go find those jets, but the were not anywhere in the engine so I assumed someone had taken them out. Seemed to run fine, lol. But yeah, those hole were pretty big......
They did not look like pipe-thread to me. More like the bung-plugs that you see in oil-drums.
But that is an oooold memory.
 
Well if you're gonna have to run a tap thru those holes anyway you could go to the next closest convenient size or even ream it out a bit to the next appropriate tap size.
Good chance it's plugged up beyond what can be seen, anyway. If you do thread something in there be generous with red loctite/
Maybe the /6 is different from what was used on other engines? Or ones with an EGR are finished different?
When floor jets were used that was the original EGR before they had àn external EGR valve.
 
They are a special coarse thread. I doubt you will find a plug. I took my jets out and welded them closed.
 
9/16-12 thread. I have a couple extra stainless bolts, 1 in long. I'm not sure how long they should be.
 
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