Rams Horn smog port plugs

[ga-stepside]

Is there a need to use thread sealer on the smog port plugs in Rams Horn manifold? The port use ¼ - 18 pipe thread plugs. If so what do you recommend as a high temp sealant?

[B. W.]

No need for sealer. Crank 'em in, they won't leak.

[ga-stepside]

Originally Posted by B. W.

No need for sealer. Crank 'em in, they won't leak.

Thanks that is what I thought just wanted to be sure. When I did this on my AMX back in the day they were not pipe threads. They were 9/16 so I used spark plug washers to sea them.

[Steeveedee]

Those are threaded for a 5/16" B-nut. You can buy plugs in that size that will thread all the way in and seat on the tapered seat in the manifold. Pipe plugs work, but only thread in a little way, and can cause cracking from thermal cycling, and the bolts may or not make a true seal with the manifold. The Air Injection Reactor pipes were 5/15" tubing, just like a fuel line.

[ga-stepside]

Originally Posted by Steeveedee

Those are threaded for a 5/16" B-nut. You can buy plugs in that size that will thread all the way in and seat on the tapered seat in the manifold. Pipe plugs work, but only thread in a little way, and can cause cracking from thermal cycling, and the bolts may or not make a true seal with the manifold. The Air Injection Reactor pipes were 5/15" tubing, just like a fuel line.

That is not what I wanted to hear. The manifolds I have use 1/4-18 pipe thread for those ports for sure. I did order some plugs from Ecklers. I just assumed they were 1/4-18.

[Steeveedee]

Originally Posted by ga-stepside

That is not what I wanted to hear. The manifolds I have use 1/4-18 pipe thread for those ports for sure. I did order some plugs from Ecklers. I just assumed they were 1/4-18.

A lot of people did this back in the day. You may be alright with the pipe plugs. I'm just one of those anal-retentive guys who goes into the details.

[ga-stepside]

Originally Posted by Steeveedee

A lot of people did this back in the day. You may be alright with the pipe plugs. I'm just one of those anal-retentive guys who goes into the details.

The plugs are on the way so I will find out next week.

[stsalvage]

If you have a problem and you have a cracked exhaust manifold i have a few i sell ya one

[Gregski]

I don't like the look of the plugs so I bought brand new ram horns and am very happy with them, nicer cleaner look, on a total piece of garbage truck, LOL

[ga-stepside]

The plugs I ordered from Ecklers came today and they fit perfectly. So the port is 1/4-18 pipe thread.

[kwmech]

No it's not, the both share the same 18 threads per inch where the pipe is tapered threads. Steeeve is correct stating that you actually need a tubing plug to get it correct. The pipe plugs will seal, but they can also crack the manifold if you crank them in too tight

[ga-stepside]

Originally Posted by kwmech

No it's not, the both share the same 18 threads per inch where the pipe is tapered threads. Steeeve is correct stating that you actually need a tubing plug to get it correct. The pipe plugs will seal, but they can also crack the manifold if you crank them in too tight

Okay, I am sure you are correct. I certainly know nothing other than 1/4-18 pipe thread fit. But the fittings I got came from Ecklers and they say they are correct for this so I'm going with that, hopefully they are the fittings you are talking about.

[Steeveedee]

If the plugs threaded in a few turns and bottomed out, you should be OK. It looks like you got straight pipe threads, which will not force a cone into the outside edge manifolds, which is where the crack would start.

[harpo231]

"National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal."


From my little black book...

[Gregski]

Originally Posted by harpo231

"National Pipe Thread Taper (NPT) is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight and therefore make a fluid-tight seal."


From my little black book...

thanks, can you learn us how they come up with their crazy 1/8th, 1/4" and 1/2" sizes?

[harpo231]

How to Determine NPT (National Pipe Thread) Size
Male NPT is denoted as either MPT or MNPT
Female NPT is either FPT or FNPT
Pipe thread sizes do not refer to any physical dimension.
The outside diameter of each pipe fitting must be measured and compared to the table for size identification.

For example, a 1” MPT pipe thread has an outside diameter of 1.315”
NPT Size Thread Diameter
OD of MPT
(ID of FPT will be
slightly less than this.)Number on right is OD of pipe
1/8” 0.405”
1/4” 0.540”
3/8” 0.675”
1/2” 0.840”
3/4” 1.050”
1” 1.315”
1-1/4” 1.660”
1-1/2” 1.900”
2” 2.375”
2-1/2” 2.875”
3” 3.5”
4” 4.5

[Steeveedee]

Originally Posted by Gregski

thanks, can you learn us how they come up with their crazy 1/8th, 1/4" and 1/2" sizes?

That is the nominal inside diameter.