Hi all - new member here. Lurker for a while. I just picked up a 1982 D150 with a slant. Been driving it for a couple of days when it sounded like the exhaust flange broke from the manifold. Turns out there must have been a plug in a large hole on the firewall side of the manifold right below the heat exchanger. I did my best with what I had (a brass pipe plug and some epoxy) but that didnt last long from the heat cycle.

Can anyone tell me the thread pitch/dimensions/etc of that hole? I'd like to pick up an iron plug that will hopefully not heat cycle as hard.

Really the brass plug should have been fine if it threaded into the manifold?

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

It threaded in, but loosely. I did my best to figure out interior thread diameter with a caliper and get something close at the hardware store.

Sounds like maybe it is a late model manifold with the hole for the O2 sensor. Is it a fine thread about 3/4" in diameter?

If so you can get a plug off E-Bay cheap enough.

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Official Cookie and Mater Tormentor.

If this is correct, most auto parts stores should have a steel O2 sensor "plug" that can be installed.

It should be a standard 18 mm O2 sensor plug. There are steel ones all over the place, including eBay. Not sure if there's a thread sealant recommended for these.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

I used RTV Copper since that's about as high temp as you can get over the counter... after a while driving it'll carbon up and seal anyway...

Dorman 65220 oil pan plug (18mm x 1.5 thread, 19mm hex head)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

An oxygen sensor will plug that hole really well and let you run an air/fuel ratio gauge to help tune your motor.

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Casually looking for a Clifford hyperpak intake for cheap.

Awesome - thanks for the info! I'd love to run an O2 sensor as it was my plan for tuning anyways. Hopefully the shop manual comes soon so I can start seeing what the PO did and didn't do when they removed all the smog equipment.