<p>I'm new to this game, and recently upgraded the hotend on my Ender 3 Pro to a <em>clone</em> of an E3D V6, as I'm keen to do nylon prints at some point. I noticed however that this one I got has a teflon liner which seems to negate the advantage of a metal hotend entirely.</p>
<p>I'm wondering what temperature it's safe to run this hot end up to?</p>
<p><a href="https://i.stack.imgur.com/6Uth3.jpg" rel="nofollow noreferrer" title="Teflon insert#2"><img src="https://i.stack.imgur.com/6Uth3.jpg" alt="Teflon insert#1" title="Teflon insert#2" /></a></p>
<p><a href="https://i.stack.imgur.com/QazJ2.jpg" rel="nofollow noreferrer" title="Teflon insert#1"><img src="https://i.stack.imgur.com/QazJ2.jpg" alt="Teflon insert#2" title="Teflon insert#1" /></a></p>

It depends how
deep
it goes. If the teflon goes into the hotend then yes, it will limit the temperature end.
But: the teflon may just be something that ends
somewhere
in the cold side and sticks out so there is something to put into the extruder or higher up into the connector.
I cam currently setting up a Slice Mosquito for a Bondtech DDX. The Mosquito is full metal, but there is a (actually printed nylon) adapter for the DDS. In this adapter you put a teflon/capricorn tube, that ALSO sticks out only around 5 mm. Here is the point though: it never goes into the even cold side and is only there so the connection to the extruder on top has a width limitation.
So, it really depends how
long
this tube is (and no-one here will know because a v6
clone
may be different internally from the original). I would suggest pulling it out (it should move out easily) and then seeing how deep it goes. As long as it stays on the cold side before the heatbreak, it never gets in touch with anything that is hot.