boost source Size Garrett gt28 gen2

[timmy94]

Tried to make 1/8npt threads into compressor house of the turbo for my EBC. Threads got fu#ked and ended up with and elongated hole, so I do have good amount and nice threads 90% of the hole but 10% I only had 1-2threads there and rest of it is flush on that side of the hole..

So my idea is to do M12 x 1.25 to AN4 with braided lines instead of 1/8npt to 4mm vacuum silicone hose. 
and hopefully get a better thread.

M12 is quite big and AN4 is a little bit bigger than 4mm (4.9mm inner diameter braided PTFE hose).

but this should work. Thoughts?

Otherwise I will weld and adapter onto the turbo. 

 

Edited Wednesday at 09:00 PM by timmy94

[GTSBoy]

If there's enough meat in the housing where you want to put the M12 adapter, then do it, but be aware that if/when you f**k that up you'll probably be repairing it before doing anything else.

I'd just drill it out and tap ina 1/4" thread. No need for rocket surgery when the next most obvious thing will do. You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

[timmy94]

3 hours ago, GTSBoy said:

If there's enough meat in the housing where you want to put the M12 adapter, then do it, but be aware that if/when you f**k that up you'll probably be repairing it before doing anything else.

I'd just drill it out and tap ina 1/4" thread. No need for rocket surgery when the next most obvious thing will do. You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

ok.

Yea, then I would need to remove the turbo and weld an adapter on to it instead, if I fuc* this one up.

 

[TurboTapin]

11 hours ago, timmy94 said:

ok.

Yea, then I would need to remove the turbo and weld an adapter on to it instead, if I fuc* this one up.

 

You just need to remove the compressor housing, not the entire turbo. I would not be drilling and tapping anything with the housing still on anyways. 

[timmy94]

6 hours ago, TurboTapin said:

You just need to remove the compressor housing, not the entire turbo. I would not be drilling and tapping anything with the housing still on anyways. 

Impossible to remove the housing while turbo is installed on the manifold on the engine. So I have to do it anyways. I plugged it so there will not be any debris in there. Will vacuum aswell 

[TurboTapin]

15 hours ago, timmy94 said:

Impossible to remove the housing while turbo is installed on the manifold on the engine. So I have to do it anyways. I plugged it so there will not be any debris in there. Will vacuum aswell 

I'm surprised to hear that, but then again, I haven't dealt with a low mount turbo in years. I'm presuming it's a space restriction issue. Cheers!

[timmy94]

On 15/8/2025 at 2:05 PM, TurboTapin said:

I'm surprised to hear that, but then again, I haven't dealt with a low mount turbo in years. I'm presuming it's a space restriction issue. Cheers!

Probably gonna remove manifold and turbo. I’m not sure if I can get M12 x 1.5 air tight. Could use high temp Loctite 246 or something similar, but I don’t know. Maybe it’s just best to remove everything again and weld an 1/8NPT on there instead.

[MBS206]

3 hours ago, timmy94 said:

Probably gonna remove manifold and turbo. I’m not sure if I can get M12 x 1.5 air tight. Could use high temp Loctite 246 or something similar, but I don’t know. Maybe it’s just best to remove everything again and weld an 1/8NPT on there instead.

Why are you so adamant on going M12?

Why not follow Brad (GTSBoy) suggestion.

You're talking moving from a 1/8" size, to a 1/2" effectively. 4 times bigger. Why skip the commonly available sizes in between?

The bigger you go, the more likely you are to strip the threads out at a later date, as guaranteed, someone will put a huge spanner on the M12 and really tighten it up, and you're only in thin wall, so not a lot of threads to engage!

[timmy94]

2 hours ago, MBS206 said:

Why are you so adamant on going M12?

Why not follow Brad (GTSBoy) suggestion.

You're talking moving from a 1/8" size, to a 1/2" effectively. 4 times bigger. Why skip the commonly available sizes in between?

The bigger you go, the more likely you are to strip the threads out at a later date, as guaranteed, someone will put a huge spanner on the M12 and really tighten it up, and you're only in thin wall, so not a lot of threads to engage!

1/8NPT drill size = 8.7mm. Since the hole got messed up by me, it’s probably around 9mm. 
 

So 1/4” NPT would be next step. A drill size of around 11mm would be preferred there which is not way of my M12 (drill 10.5mm and tap M12 threads) 

[Dose Pipe Sutututu]

Just throwing around ideas, does it need to be in the compressor cover?

Why not the hot side piping?

[GTSBoy]

On 14/08/2025 at 9:20 AM, GTSBoy said:

You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

Because pipe threads for pipe things. M threads for bolt things.

Throw some teflon sealant onto it and dust your hands off knowing you did the right thing, instead of going twice around the block to achieve a result using the wrong things.

Of course, all of these solutions are ignoring the fact that the minimum thread pitch we're talking about here is 1.25mm, with the 1/4" in NPT or BPS being out around 1.4mm. You will need to know that the boss you're tapping has enough thickness for at least a few threads. That's one of the reasons that 1/8" is commonly used - because the pitch is <1mm.

And why would you look to use 1/4" NPT in a BSP country anyway? Ugh.