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Hello everybody and thank you in advance,
I'm removing the smog pump from my engine. I've pretty much figured out what I need to do. My only question is does anybody know what size plugs I'll need for my manifold? I don't want to plug the hoses, I want them gone for a nice clean engine bay. So what size and where can I get them? Thank you!
Another question fellas. I got the holes plugged nice and easily, but I have one big one now where there is an aluminum hose? Not sure if that's the best description, but I have attached a picture of it. The hose is still attached in this picture, sorry I should have gotten one without being attached. But does anyone have any ideas of how to plug this?
The TPI exhaust manifolds just screw in.. I took some 1/4 NPT square head plugs and put back in place after i unscrewed the pipe fittings. Clean as can be.
Yeah, that's the pipe thread size I mentioned earlier that's close to the 5/16" inverted flare that they actually are, such that it works largely OK even if not absolutely the right thing.
It's actually 1/2"-20, which is a bolt thread (not pipe thread). Not sure where Sofa is getting 5/16", unless perhaps later models use that size, but my exhaust manifolds are '84...
EDIT: Okay, I think the inverted flare fitting is for 5/16" tubing. The threads are 1/2"-20.
It's 5/16" tubing, with an inverted flare fitting made onto on the end. Just like, the fitting on your Q-Jet fuel inlet, is 3/8" inverted flare. Same type of fitting, different tubing size. Some carbs come with 5/16" inverted flare inlets, too.
What the nut diameter and thread pitch is, or the hex drive (which for 5/16" inverted flare, is 9/16"), is a whole other matter.
The fitting size is 5/16" inverted flare. Which a ¼" NPT plug (similarly, ¼" isn't the fitting diameter, it's the nominal pipe size) is close enough to, that it will thread in far enough (usually) to seal well enough for the situation at hand, even if not perfect.
Last edited by sofakingdom; Mar 10, 2021 at 07:11 AM.
It's 5/16" tubing, with an inverted flare fitting made onto on the end. Just like, the fitting on your Q-Jet fuel inlet, is 3/8" inverted flare. Same type of fitting, different tubing size. Some carbs come with 5/16" inverted flare inlets, too.
What the nut diameter and thread pitch is, or the hex drive (which for 5/16" inverted flare, is 9/16"), is a whole other matter.
The fitting size is 5/16" inverted flare. Which a ¼" NPT plug (similarly, ¼" isn't the fitting diameter, it's the nominal pipe size) is close enough to, that it will thread in far enough (usually) to seal well enough for the situation at hand, even if not perfect.
Yeah, makes sense. And if I remember right, the actual thread size is 1/2"-20...
They are not 1/2-20, they are the same thread as 1/4npt plugs but not tapered 5/8"-18.
Tapered 1/4npt pipe plugs may or may not seal, depending on the plug, 1/2-20 will sort of go in, but will never seal perfectly. I use 5/8"-18 Allen head "grub screws" for the cleanest look (they just go in with nothing sticking up, but the next best thing is a 5/16 flare plug, but that will usually be brass and have a small hex sticking out. Both of those will seal correctly and be removable later if you have to for some reason.
They are not 1/2-20, they are the same thread as 1/4npt plugs but not tapered 5/8"-18.
Tapered 1/4npt pipe plugs may or may not seal, depending on the plug, 1/2-20 will sort of go in, but will never seal perfectly. I use 5/8"-18 Allen head "grub screws" for the cleanest look (they just go in with nothing sticking up, but the next best thing is a 5/16 flare plug, but that will usually be brass and have a small hex sticking out. Both of those will seal correctly and be removable later if you have to for some reason.
They ARE 100% 1/2"-20 bolt thread. I posted 2 pictures of them previously and it should be obvious that they fit (not just "sort of"). There is no reason to use a flare fitting after the tubes have been removed.
NPT is tapered; that's what makes it a pipe thread, which is absolutely NOT what those exhaust manifold air injection holes are tapped for.
A 5/8" is too big and wouldn't even fit in the hole, not to mention that the thread pattern doesn't match. There's a huge difference between 1/2-20 and 5/8-18...
