Inspired by the GRM Chump Car and my own leaking prop. valve I've ordered a Speedway adjustable proportioning valve ($39 with shipping!) for the rear brakes.
The Speedway prop. valve body has NPT (a.k.a. national pipe thread) fittings and i'm concerned about getting a good seal and avoiding leaks / sudden drops in pedal pressure.
Should I used a thread sealant, like the ARP goop, or the Loctite thread sealant, or just trust that they won't leak?
i'd appreciate some input on this 
I have never used any sealants on brake pipe threads. Pipe threads by design are supposed to seal themselves up.
Ranger50 wrote: I have never used any sealants on brake pipe threads. Pipe threads by design are supposed to seal themselves up.
Right, but regular brake threads are double flare / bubble flare etc. This is an NPT pipe thread, which is different.
fifty wrote:Ranger50 wrote: I have never used any sealants on brake pipe threads. Pipe threads by design are supposed to seal themselves up.Right, but regular brake threads are double flare / bubble flare etc. This is a pipe thread.
yes, and pipe threads seal themselves up..
Thanks guys! I was overthinking the problem.
here's a hotlink to the Flyin' Miata install direction - no mention of plumbers dope, brazing, JB Weld or white bread with no crust etc. I think I'll be fine. 
http://www.flyinmiata.com/support/instructions/suspension/proportioning_valve.pdf
If the NPT fitting is brass and the prop valve is steel or brass then the NPT fitting should seal if you tighten it enough. You could use a bit of teflon tape, just don't leave any near the end of the threads. Another alternative is some blue thread locker.
I don't see why they do this, NPT threads on a brake part? Wilwood does as may others do as well.
jimbbski wrote: If the NPT fitting is brass and the prop valve is steel or brass then the NPT fitting should seal if you tighten it enough. You could use a bit of teflon tape, just don't leave any near the end of the threads. Another alternative is some blue thread locker. I don't see why they do this, NPT threads on a brake part? Wilwood does as may others do as well.
they do it because it works, and also because it's easy and cheap to find whatever flare adapters you might need to hook it up locally at any decent auto parts store..
fifty wrote: Thanks guys! I was overthinking the problem. here's a *hotlink* to the Flyin' Miata install direction - no mention of plumbers dope, brazing, JB Weld or white bread with no crust etc. I think I'll be fine.
What's not mentioned in those directions is that the FM adapters come with teflon paste (not tape) on the threads of the fittings already. So do the SAE ones that ship with the Wilwood prop valve. You may not need it, but it doesn't hurt.
I've always used Teflon tape and never had a problem.
No sealant on pipe threads makes me feel kinda icky. If the threads are imperfect, you have to tighten them heavily to deform the metal, and some things will not tolerate that much tightening before the female-threaded part cracks. Especially since so many of these parts seem to be spindly little over-machined aluminum things.\
Plus, the Teflon tape ensures that you're able to remove the fitting again.
FYI - i have purchased wilwood and summit racing adjustable prop valves(both made by wilwood) and the adapter fittings they come with for the npt to flare connection come with their own orange sealant on the pipe threads.
Always use sealer on tapered pipe thread. Thats part of the design.
the prop will come with brass adapters, NPT male on one end and some type of flare female on the other end. the male end will probably have orange sealant on the threads, as mentioned earlier. the seal between the prop and the adapter is at the thread. the seal between the adapter and the brake tube is at the flare.
Thanks guys! As a footnote, the Speedway valve looks exactly like the Wilwood one, with the exception that the brass adaptors have no sealant on the threads. I have some Loctite sealant, so i'll go with that.
Its my understanding that the teflon tape / pipe dope is not intended to be a sealant on NPT fittings but a lubricant for the threads.
KJ
Knurled wrote: I've always used Teflon tape and never had a problem. No sealant on pipe threads makes me feel kinda icky. If the threads are imperfect, you have to tighten them heavily to deform the metal, and some things will not tolerate that much tightening before the female-threaded part cracks. Especially since so many of these parts seem to be spindly little over-machined aluminum things.\ Plus, the Teflon tape ensures that you're able to remove the fitting again.
the teflon will decrease the friction, which allows you to put even more torque on the threads if you aren't careful. the end result could be just as broken as if you crank it in too tight dry, only with less effort required to do it.
$39 for an adjustable prop valve? Me likey! 
Taiden wrote: $39 for an adjustable prop valve? Me likey!
that's what i paid for my Wilwood adjustable prop valve 10 years ago..
Taiden wrote: $39 for an adjustable prop valve? Me likey!
http://www.speedwaymotors.com/Speedway-Purple-Proportioning-Valve,23498.html
And it's PURPLE!!!!!! YES!!!
novaderrik wrote:jimbbski wrote: If the NPT fitting is brass and the prop valve is steel or brass then the NPT fitting should seal if you tighten it enough. You could use a bit of teflon tape, just don't leave any near the end of the threads. Another alternative is some blue thread locker. I don't see why they do this, NPT threads on a brake part? Wilwood does as may others do as well.they do it because it works, and also because it's easy and cheap to find whatever flare adapters you might need to hook it up locally at any decent auto parts store.. Doesn't make it right! I had a Kelsey-Hayes prob valve on a race car and it used normal inverted flare fittings. Sinple to plumb and less connections to possible leak!
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jimbbski wrote:novaderrik wrote:jimbbski wrote: If the NPT fitting is brass and the prop valve is steel or brass then the NPT fitting should seal if you tighten it enough. You could use a bit of teflon tape, just don't leave any near the end of the threads. Another alternative is some blue thread locker. I don't see why they do this, NPT threads on a brake part? Wilwood does as may others do as well.they do it because it works, and also because it's easy and cheap to find whatever flare adapters you might need to hook it up locally at any decent auto parts store.. Doesn't make it right! I had a Kelsey-Hayes prob valve on a race car and it used normal inverted flare fittings. Sinple to plumb and less connections to possible leak!
that's all well and good, but what if the car you are plumbing uses a different size flare than what comes built into the prop valve? then you need an adapter in the system somewhere, which as you pointed out, is another potential leak.
using NPT threads allows them to make 1 part that is universal, which makes it cheaper. if they had to make a different part for every different size and style of flares, the price would go up more for each part than what you'll spend at NAPA getting a couple of NPT to flare adapters to use the universal piece.
Of course, there are some NPT to flare adapters just not found in nature. Such as NPT to metric inverted flare. You know, the sort that's used on a lot of those import cars. Someday they're gonna catch on, then we'll have to start selling parts for 'em.
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