hola friends- could any gurus out there drop some knowledge on me? I'm cleaning out the threads on the thermo vacuum plugs, on the intake side of my 22r. My tap/die set doesn't have a big enough tap. I am thinking it looks like 16mm? Don't really have a good handle on this stuff. My 14mm x 1.25 tap was too small but it looked like it was about the right pitch.

Anybody have a ruling on this one?

 

As a matter of fact I do(as far as the type of tap you're looking for). They are most likely going to be threaded PT-JIS(Japanese Industrial Standard Taper Pipe Thread). Functionally interchangeable with R-BSPT(British Standard Taper Pipe Threads, External). IOW, you're screwed(pardon the pun).

 

he's correct, BSPT.
for the axle housings too (if your making breather extensions.)

 

Thanks to you both for your help!
In case someone else has this question, I think this link contains the precise answer, http://www.lceperformance.com/Intake...-p/1032050.htm

I believe the thermo vacuum plugs are 19 jspt.

 

I think it does not. But that's more of an opinion. What's wrong with it you ask? Well first off, as you've alluded to, things manufactured in Japan typically aren't measured in inches. So there's really no such thing as ⅜" JSPT. ⅜" ≈ 9.5 mm. Secondly, there's definitely no such thing that's even roughly equivalent to ⅜" JSPT straight. The T in JSPT refers to Taper(if it's Taper, IT'S NOT STRAIGHT). Thirdly, there's no such thing as a shouldered plug. 2 types only, Taper or Straight.

In conclusion, they couldn't have stated any of that any more inaccurately if they tried. What a bunch of dumbasses..IMO.

 

As much as I want to agree, Mud, I withhold agreement for a moment.... LCE has done me right many times, and experience has taught me to trust their guidance until proven otherwise.

In this case, I wonder if 3/8" could refer to the squared end size, opposite the "tap" end. Similar to 3/8 vs 1/2" sockets. What say you?

So in this example, the 19 would be 19mm (tap size) and the 3/8 would be 3/8" driver size-- or something like that.

 

Generally, "straight" fittings are machined with some sort of shoulder to provide the sealing surface (o-ring, gasket). Tapered fittings don't need/have that. http://www.malonespecialtyinc.com/Id...g_Threads.html So I would think that LCE would describe the two plugs as "shouldered" and "tapered," not "shouldered" and "straight."

So LCE might be providing the appropriate fittings, but I, too, have a little difficulty following their description.

 

Sooooo... if we can't trust LCE's list of plugs:

http://www.lcengineering.com/LCInstr...Plug%20Kit.pdf

... but we want to source our own, exactly which sizes/styles would we be seeking?

AND-- where do we even find this sort of thing at all? Local hardware and plumbing supply stores (including big box places like Home Depot, Tractor Supply, etc) carry next to nothing like this and I can't find any place online from which to order, either.

 

The specific link

http://www.lcengineering.com/LCInstr...Plug%20Kit.pdf

pictures an AFTERMAEKET INTAKE MANIFOLD.

This manifold pictured is made by Offenhauser - and "American" company (they made their fame as one of the early manufacturers of intake manifolds for engines that won the Indy 500 way back when - like 1940s?)

So that kit would likely have "SAE" or "American" type fittings.

Yes, I know, I read the text, and LCE claims that the plugs ALSO fit the 22R head.

BTW - an OEM Head Gasket kit comes with several of those plugs - probably because the intake could be either Carb (22R) or EFI (22RE) so they include parts for both.

Thread gauges are readily available at Lowes and Home Depot and Sears
They come as "standard" (i.e. SAE) and "metric"

But perhaps I misunderstood the question.
If you are looking as to where to "source" these plugs, I'd go with 22RE Performance

http://www.22reperformance.com/parts...ild-parts.html

And to make things REALLY confusing - there is a "Japanese Pipe Thread" spec that uses "English" markings
So there really is a 3/8-19 "japanese" pipe taper
Also - the 19 usually refers to "turns per inch" or the number of threads in one inch

(see at the bottom chart on here)
https://mdmetric.com/tech/thddat7.htm