I need your help with my vacuum tap (and my manifold studs, too).
Mopar Guys/Gals: I could use your advice on my 1974 Duster's intake manifold power brake booster vacuum tap. The first photo is of the existing tap in the intake manifold of my slant six. Like many things on my motor, it had been changed out with an incorrect part years ago. My engine should have the single tap with no nipples coming off it since it is a non-a/c car. The second photo is the correct tap that I'm installing on my engine. The diameter is 11/16" with either NPT or fine threads on it, and it takes an 11/16" open end wrench to remove it. As you can see, the old tap was only threaded about halfway into the manifold. When I removed it, the bottom half of the female threads inside the intake manifold appeared to be dirty and a bit rusted, although not damaged or stripped. My first question is this: How far should this fitting be threaded into the intake manifold? Logic tells me that it should be threaded all the way down to the shoulder on the fitting itself. But as you can see, the old tap won't go in any further because it stops threading about halfway down. I suspect the threads in the manifold are contaminated and prevent the fitting from threading fully into the intake. What do you think? Should this thing go all the way down? The length of the threads on the fitting is the same as the depth of the female threads inside the intake manifold. Should I put some nylon tape or pipe dope on it prior to installation to ensure a vacuum tight seal? Should this fitting be painted engine color or left natural metal? I've heard of something called a thread chaser before, and I believe it is used to clean out contaminated female threads. I've never used one, so forgive me for asking such a basic question, but should I chase the threads in the intake manifold so that my fitting will go all the way in? Thanks in advance for your advice. Finally, the studs that attach my intake/exhaust manifold to the cylinder head appear to be several different lengths. Shouldn't they all be the same? Slant six experts, what is the correct stud length and fastening bolt for my engine? Does anyone sell this in a kit, or do I just buy them at NAPA? Thanks for the help!
Mopar Guys/Gals: I could use your advice on my 1974 Duster's intake manifold power brake booster vacuum tap. The first photo is of the existing tap in the intake manifold of my slant six. Like many things on my motor, it had been changed out with an incorrect part years ago. My engine should have the single tap with no nipples coming off it since it is a non-a/c car. The second photo is the correct tap that I'm installing on my engine. The diameter is 11/16" with either NPT or fine threads on it, and it takes an 11/16" open end wrench to remove it. As you can see, the old tap was only threaded about halfway into the manifold. When I removed it, the bottom half of the female threads inside the intake manifold appeared to be dirty and a bit rusted, although not damaged or stripped. My first question is this: How far should this fitting be threaded into the intake manifold? Logic tells me that it should be threaded all the way down to the shoulder on the fitting itself. But as you can see, the old tap won't go in any further because it stops threading about halfway down. I suspect the threads in the manifold are contaminated and prevent the fitting from threading fully into the intake. What do you think? Should this thing go all the way down? The length of the threads on the fitting is the same as the depth of the female threads inside the intake manifold. Should I put some nylon tape or pipe dope on it prior to installation to ensure a vacuum tight seal? Should this fitting be painted engine color or left natural metal? I've heard of something called a thread chaser before, and I believe it is used to clean out contaminated female threads. I've never used one, so forgive me for asking such a basic question, but should I chase the threads in the intake manifold so that my fitting will go all the way in? Thanks in advance for your advice. Finally, the studs that attach my intake/exhaust manifold to the cylinder head appear to be several different lengths. Shouldn't they all be the same? Slant six experts, what is the correct stud length and fastening bolt for my engine? Does anyone sell this in a kit, or do I just buy them at NAPA? Thanks for the help!
