So on my 1983 Dodge D150 with the /6, I was going through making sure the manifold / exhaust stud nuts would come out after a few days of soaking them with Free All, the gasket is already blown so I wasn't really worried about disturbing it, luckily no one has monkeyed with this engine and the acorn nuts and triangles are all present. I'm sure the gasket has been done as this is a high mileage engine, but the two studs that concern me the most are the two to the exhaust flange that connects to the pipe below. If I cant get them loose, or figure out what size they are, and I'm running out of sockets to try, I'm gonna have to cut the down pipe and have my exhaust guy fix it. I don't want to do that because that flange is leaking and since I put a muffler back on this truck (It was sitting for 10 years and the old one was full of mouse house), the only thing I hear is the exhaust leaks under the hood. Also I'm pretty sure the gasket is blown letting exhaust into the intake, but I'm not 100% sure on that.

Anyway, attached below is a picture of the two nuts I'm talking about, of course the dipstick is in the way so I might pop that out of the block while I'm working. I can't find a socket that really fits, a 16mm comes close, I know they're standard but uh, I'm running out of tools in my mishmash kit

I appreciate the help, I'm trying to round up the tools I need to get this job done quick, I do not plan on separating the exhaust and intake manifold if I can help it, it isn't leaking there.

What sizes have you tried? Are you using 6 point or 12 point sockets or box end wrenches? Last question: was the 16MM too large or small?

I think I had one 5/8 and one 11/16 nut on my truck.. I remember that they were two different sizes..

Should be 7/16 - 14 (coarse thread) studs.

Lou

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Those two are the least of your worries.
Yes 7/16-14 is right.
Usually takes a 5/8" wrench/socket.
Could be rusted, eaten away from age and all the heat cycles.
But of all of the exhaust bolts on the engine (pipe flange, bolts that hold the manifold to the engine, bolt/studs that hole the manifolds together) the ones that hold the pipe to the manifold are the ones that if they broke, and if you drilled them and were "off" and wrecked the threaded holes, those are "open" on top where you could use a nut on the top side in place of the threads in the manifold. And open so you could get some heat on the ears of the flange to help work them loose. And a little propane hand held bottle torch won't touch it. The same setup with a mapp bottle has a better chance, but you really need a big oxy acetylene setup to make a dent.
Or an inductive heater like a "bolt buster" applied to the head of the bolt til it goes red (would take less than a minute each with one of those) and BE READY with the right socket to get on the head of it and slowly working it back and forth and reapply heat til it works loose.

T'were me, I wouldn't waste much more time trying to finesse them off. I'd just get a Harbor freight electric grinder with a cutoff wheel, and grind on one of the flats until I saw threads. You risk breaking off the studs with trying the "rust-juice" and wrench thing.

But then, I hate exhaust work.....Roger

5/8 is too small and 11/16 is too big on either nut, that's what's got me confused, a 16mm socket kind fits the front one but not well enough I'd trust it. I've tried open and box ended wrenches and sockets.



Oh trust me, I'm very tempted to take my grinder to these, get 'em just down before the threads and break them off. The smog pump needs to go, and so will the dipstick if I am to have enough room. Ditto on hating exhaust work but the exhaust leaks upwards and I had to get creative with my fuel line routing because it was heating up the fuel line. I mean I could just do the right thing and make a flimsy metal "heat shield" to divert the ehaust away, but I'd rather just do the extra right thing and try to get this thing loose.



So from two people telling me there should be a 5/8 socket on there tells me these are the wrong nuts, and probably not an actual size anymore. I don't have access to fancy torches but I do have a grinder, so as said above, that may come into play.

Surprisingly all the nuts holding the manifold to the head came loose, if I can just get these two supposed to be but aren't 5/8 nuts loose I'll be set, or grind them off, clean the studs, and thread new ones on. One way or another these are coming off.

It uses a short 11/16" open wrench on the back nut and a closed 11/16" on the front one. You could always cut the exhaust pipe, remove the manifold and work on a bench to get to the nuts. They are a pain when they rust up.

If I were trying NOT to remove the exhaust manifold from the engine, I might make an attempt with a file on the rear nut to file some flats on ether side of the nut, and use an open end wrench.

Or a 6" pipe wrench (not much bigger than your hand) that I just tried, and found it will fit enough to remove the nut with lots of repetitive motion.. but off, is off....

IF you decide to cut the exhaust pipe, I've successfully marked them with a line or two parallel to the direction of the pipe so they can be "clocked" when off the vehicle and welded together..

Better yet if you cut it in a flat place where the pipe is straight, you can use a "band clamp", to reattach, and or drive the truck to your welder/exhaust repair. Be extra careful when cutting above yourself.. a face shield or some sort of good eye protection is a whole lot better than wasting a day getting grit out of your eyes..

Yeah they aren't 11/16 anymore, they've shrunk, I'm gonna try to grind them down to get an open ended wrench on them before grinding them to the point I think I can break them without damaging the studs. Unfortunately I've been here before and I was hoping I was just missing a size somewhere.



Yeah I came to that conclusion today, as said above these nuts are gonna meet the grinder, hoping I can strategically remove enough material to evict them without damaging the studs or the flange. And yeah, I don't mess around with wearing safety glasses, I like my eyeballs.

Anyway I have to replace the combination intake / exhaust gasket, I've got a Fel-Pro set, should be good.