Tapping for a tapered thread.

[DaveL485]

I need to tap an alloy manifold to take an injector. The injector has a thread on its collar but it's a tapered thread...as in it gets wider on the way up the thread. Pic should show this.



Googling seems to return results for tapered taps (see below)



This is the style I have now for normal holes....the tap tapers but the thread it creates does not, it's kind of a nose-in to the hole.

Does anyone know 1)The proper name for the tapered thread (Unless its just tapered thread) and 2)Do I need a special type of tap to thread the hole in the manifold? I can't see it going in to a standard straight thread properly, tbh. Also I dont want to chemical metal them in as it's under pressure (Turbo) and I might want them out again at some point.

Thanks in advance.

[DaveL485]

Patrick Bateman said:

You'd need to know what kind of thread it was.

NPT, BSP, BSF etc.

Yes, its definitely not Metric, but I can find out the thread with a quick visit to Pirtek or similar.

[DaveL485]

Thanks everyone- very educational.

Whats posted above has led me here- http://en.wikipedia.org/wiki/National_pipe_thread

I'm pretty sure what I have is a 1/8th NPT thread, which in turn has shown up a few taps on eBay and the like....although the point about using a straight thread is interesting. Maybe this will be more appropriate in a soft material like the alloy manifold i'll be fitting to.

I'll have a ring around the various companies now I can sound like I half a clue what im on about and see what they recommend (Straight or tapered hole). In case you haven't guessed already, it's a Nitrous Oxide fogger nozzle, one of which will land in each of 4 inlet branches

[DaveL485]

Certainly won't be 10,000PSI!

Manifold pressure should never spike over 30, unless something goes horribly wrong

As long as it doesn't come out while it's spraying N20 and fuel out at a rate of knots i'll be happy!

[DaveL485]

shovelheadrob said:

Fogger nozzle, 1/8 npt, use a small amount of ptfe tape and screw in gently, making sure it is in the correct orientation when finished

Yeah...pointing back up the manifold wouldn't be much cop would it lol.

Plan to seat it as far back up the inlet run as possible, pointing toward the back of the valves.

[DaveL485]

thinfourth2 said:

Do please remove the manifold before drilling and tapping the holes

Its already off....I don't fancy ruining almost £2k worth of Pistons and Liners with swarf!

shovelheadrob said:

I don't know how much you know about nitrous, but a good tool if you are going to get serious is http://www.koehlerinjection.com/nitrous-master-sof... I used to use the program when we raced a nitrous combo with a fair bit of success, it won't make you a tuning wizard, but it takes a lot of the guesswork out. Your biggest danger is detonation so make sure you take timing out.

Not used NoS before. Its a fast road car so not extreme-extreme, the plan is 25bhp per cylinder direct port. I'll be using full standalone and will be backing the timing off when I start trialling the NoS.