Port size rpm performer manifold question

[Duster Duke Boy]

I need to know what size this port is on an Edelbrock performer rpm for a small block 360 see pic?

it looks like 1/2 npt but not sure.

it goes to the heater core and I need to swap it for a 1/2 in nipple, currently has a 5/8

Thanks

 

[forphorty]

I don't own a Ed rpm, but I betcha it's 3/8 NPT. On my Speedmaster intake, the hole in that location is 3/8 NPT. Hole on PS next to thermostat housing is 1/4 NPT (on SM intake )which is what I used for my 1/2 heater hose. Hole next to it is 1/8 NPT, which I used for temp gauge. See pic :

 

[Duster Duke Boy]

I don't own a Ed rpm, but I betcha it's 3/8 NPT. On my Speedmaster intake, the hole in that location is 3/8 NPT. Hole on PS next to thermostat housing is 1/4 NPT (on SM intake )which is what I used for my 1/2 heater hose. Hole next to it is 1/8 NPT, which I used for temp gauge. See pic :

View attachment 1716192179

Thanks maybe I should swap heater to the ps hole

 

[volaredon]

3/8 npt sounds right for 5/8 hose

 

[Duster Duke Boy]

So the one on drivers side is 5/8 npt and one on pass side is 1/2 npt. just in case anyone needs that info

 

[mopowers]

So the one on drivers side is 5/8 npt and one on pass side is 1/2 npt. just in case anyone needs that info

Incorrect. @forphorty is correct in post #2. The hole on the driver's side is 3/8" NPT. The two on the passenger's side are 1/8" NPT and 1/4" NPT.

 

[Duster Duke Boy]

Incorrect. @forphorty is correct in post #2. The hole on the driver's side is 3/8" NPT. The two on the passenger's side are 1/8" NPT and 1/4" NPT.

I took them out and they measured 5/8 and 1/2

 

[TT5.9mag]

I took them out and they measured 5/8 and 1/2

NPT threads (tapered) are not measured by their actual size.

 

[Duster Duke Boy]

NPT threads (tapered) are not measured by their actual size.

then how do you convert actual size to npt size?

 

[TT5.9mag]

then how do you convert actual size to npt size?

You don’t. There is no reason to.

 

[Duster Duke Boy]

You don’t. There is no reason to.

so if it measures 1/2 in what size is it? is this like a 2x4 is not 2x4?

 

[TT5.9mag]

Edited because the link didn’t work.

 

[mopowers]

I took them out and they measured 5/8 and 1/2

Listen to @TT5.9mag . I just measured the RPM manifold that's on my shelf. Trust me. Pipe is measured by ID of the pipe itself, not by the thread dimensions. NPT is measured completely different than standard thread pitch. 5/8" NPT is HUGE.

 

[TT5.9mag]

Maybe this will help.

From left to right;
1/8 NPT
1/4 NPT
3/8 NPT
1/2 NPT

 

[Duster Duke Boy]

Listen to @TT5.9mag . I just measured the RPM manifold that's on my shelf. Trust me. Pipe is measured by ID of the pipe itself, not by the thread dimensions. NPT is measured completely different than standard thread pitch. 5/8" NPT is HUGE.

I’m just trying to learn not about not trusting, trying to understand. if I measure hole at 1/2 in how do I know what size npt it is?

 

[Duster Duke Boy]

Maybe this will help.
View attachment 1716192636

From left to right;
1/8 NPT
1/4 NPT
3/8 NPT
1/2 NPT

yes thank you!

 

[TT5.9mag]

Npt will be confusing at first, but once you work with it for a while you will recognize the sizes and become familiar with it. The taper gives it away. NPT fittings are common on anything that is supposed to retain a fluid. And use a thread sealer on them. Mostly for lubricating the threads but also to seal up. I prefer the loctite paste.

 

[Duster Duke Boy]

Npt will be confusing at first, but once you work with it for a while you will recognize the sizes and become familiar with it. The taper gives it away. NPT fittings are common on anything that is supposed to retain a fluid. And use a thread sealer on them. Mostly for lubricating the threads but also to seal up. I prefer the loctite paste.

View attachment 1716192638

Thanks

 

[mopowers]

I’m just trying to learn not about not trusting, trying to understand. if I measure hole at 1/2 in how do I know what size npt it is?

Hey no biggie. We've all gotta start somewhere. Good on you for trying to figure it. Besides the photo above, check out a standard drill chart. a 1/2-14 NPT tap uses a 23/32" drill bit (nearly 3/4") whereas a 3/8-18 NPT uses a 37/64" (about 9/16"). I reference the one on my wall all the time.

 

[mopowers]

Another good one. Just keep in mine the threads are tapered like TT5.9mag said.

 

[Duster Duke Boy]

Hey no biggie. We've all gotta start somewhere. Good on you for trying to figure it. Besides the photo above, check out a standard drill chart. a 1/2-14 NPT tap uses a 23/32" drill bit (nearly 3/4") whereas a 3/8-18 NPT uses a 37/64" (about 9/16"). I reference the one on my wall all the time.

View attachment 1716192640

I never was good at fittings but trying to get better thanks

 

[TT5.9mag]

I never was good at fittings but trying to get better thanks

You’ll be a pro in no time.

 

[volaredon]

I don't think there even is such a thing as "5/8 npt".

 

[Duster Duke Boy]

I don't think there even is such a thing as "5/8 npt".

probably why I could not find one