[tach]

I have a set of AFRs on my sb part #1034. Can someone give me the correct size for the temp sensor hole? I know the hole is 3/8" but, is it an NPT? I called AFR and they said it was a 3/8" x 18 NPS???? I went to the local parts house and they gave be the 3/8" NPT. I tried screwing that in and it will only go a few threads before it get hard to turn. If it is indeed the NPS where can I get this fitting? Thanks.

[trmnatr]

NPT, it will not screw in by hand, it should get "tight"

Use some permatex thread sealant on it

[Tom Mobley]

if you have to you can run a 3/8" NPT tap into the hole. This is the same crud Dart is doing on the Big M blocks. NPS means National Pipe Straight I think. It's a cheapskate deal IMHO. It not like they don't know people are going to be screwing tapered pipe sensors in there. I had to re-tap every pipe plug holes in the Big M block I'm currently working on. A PITA for sure.

[tach]

thanks guys. Time to go back to the parts house.

[tach]

Well, I just got back from Autozone, Ace hardware, and Tractor supply with no luck of finding the Famous NPS fitting. If you guys know of a place to find this type of fitting please chime in. I hate to try and use the NPT fitting and screw up a $1400 set of heads. AFR said use a 3/8 x 18 NPS so I'm going to call a speed shop on Monday and see if they have them. Wish me luck. If anyone is using the eliminator heads and have plugged these holes please let me know what you used. thanks guys for the help.

[Tom Mobley]

I don't think there is any such thing as an NPS fitting. It would leak anyway, nothing to tighten it up against or into. Call AFR and ask them to send you some non-leaking NPS fittings, see what they say. I'll bet it's not "Sure, we'll send a few right out."

GO back to the hardware store and buy a 3/8" NPT tap. Tap the holes out 2 threads at a time till whatever you're screwing in goes in as far as you want.

[Tom Mobley]

Ah jeez, worse than I thought. NPS = Nominal Pipe Size, it doesn't refer to a type of thread. See http://en.wikipedia.org/wiki/Pipe_(material)

[Wolfplace]

Originally Posted by tach

Well, I just got back from Autozone, Ace hardware, and Tractor supply with no luck of finding the Famous NPS fitting. If you guys know of a place to find this type of fitting please chime in. I hate to try and use the NPT fitting and screw up a $1400 set of heads. AFR said use a 3/8 x 18 NPS so I'm going to call a speed shop on Monday and see if they have them. Wish me luck. If anyone is using the eliminator heads and have plugged these holes please let me know what you used. thanks guys for the help.

=
Forget trying to find an NPS fitting, NPS is straight & has to have a washer or jam nut to seal.
NPS is the same pitch as NPT just not tapered so if it is not tapped deep or they are in fact using the NPS tap to make machining easier just take a 3/8NPT tap & chase the threads, this is not a big deal I have to do it in all Dart blocks
Annoying,, a bit but not the end of the world

[Tom Mobley]

Mike,

any idea why they would be doing this? I mean why would Tony@AFR be shipping thousands of heads that you can't screw the temp sensor into? How could straight threads be that much cheaper that tapered?

[Wolfplace]

Originally Posted by Tom Mobley

Mike,

any idea why they would be doing this? I mean why would Tony@AFR be shipping thousands of heads that you can't screw the temp sensor into? How could straight threads be that much cheaper that tapered?

=
Hi Tom,
I do not know for a fact they are using an NPS tap but the reason it would be used in CNC work is they are easier to control

You do not end up with a too deep NPT taper which is much worse than too shallow, really sucks to fix a too big hole

As you know Dart does it & it is a pain in the ass if you don't know about it ahead of time
Really sucks to find out after the short block is assembled that you have to retap all the pipe threads,,,

[tgw323]

Any recent CNC machine, which with their recent expansion they should have,uses rigid tapping. This means the tap is solidly mounted in its holder like a drill, unlike previously, where a spring loaded holder was used to prevent breakage. This means that they should be able to control the depth to thousandths of an inch. In aluminum, a good tap should last hundreds of holes. This means that they are just transferring a PITA down the line, a practice all too common in the speed industry.

[tach]

the heads are on the motor and it has been primed and is ready to go in. Heck it's attached to the tranny and on the cherry picker ready to go. Could I tap it as is or would I need to take the heads off. I'm thinking about just putting some teflon tape on the NPT fitting and running it in there a few threads and calling it good. What do you guys think?

[Wolfplace]

Originally Posted by tach

the heads are on the motor and it has been primed and is ready to go in. Heck it's attached to the tranny and on the cherry picker ready to go. Could I tap it as is or would I need to take the heads off. I'm thinking about just putting some teflon tape on the NPT fitting and running it in there a few threads and calling it good. What do you guys think?

=
People are making to big of a deal out of this

How many threads does your fitting screw in by hand or with light pressure?

Yes, if necessary you can just run a tap into the hole with no issues what so ever, you are not taking enough metal out to hurt anything but if you put some grease on the tap & almost all of the metal cut will stick to & come out with the tap if you are concerned.
Clean the hole & you are done

This is really an easy fix assuming a fix is necessary

[blumont]

Heck, I just put a bit of sealer on the plugs and screwed them in. They don't sit quite flush but they are fine and don't leak.

[3V Performance]

Originally Posted by Wolfplace

=
People are making to big of a deal out of this

How many threads does your fitting screw in by hand or with light pressure?

Yes, if necessary you can just run a tap into the hole with no issues what so ever, you are not taking enough metal out to hurt anything but if you put some grease on the tap & almost all of the metal cut will stick to & come out with the tap if you are concerned.
Clean the hole & you are done

This is really an easy fix assuming a fix is necessary

Mike, how does it go....

you can lead a horse to water but you cant make him drink......

Tom