throttle body biss screw

DSM's 4 life · 08-07-2012, 07:47 AM

I went to the junk yard yesterday and I scored a free 1g tb I went to remove the biss screw and it was almost non existant I had to drill and melt it out I then took my biss screw from my 2g tb and that snaped off inside as well I know they dont make metal screws anymore but I need something to chase the threads or something because i have plastic lodged in there and I feel like the $15 biss screw I just bought will do the same thing. anyone know what to do?

iugrad92turbo · 08-07-2012, 07:54 AM

To chase threads in that are its gonna be hard i know, i just got another tb, it may come down to that, dont see any chaser to do what you want it to, but im not ruling it out just a pita.

DSM's 4 life · 08-07-2012, 08:02 AM

Quote:

Originally Posted by iugrad92turbo

To chase threads in that are its gonna be hard i know, i just got another tb, it may come down to that, dont see any chaser to do what you want it to, but im not ruling it out just a pita.

I know they make metal ones but no one seems to have them I just purchased a new biss from STM and if it comes down to it i guess I can use my 2g tb but the 1g looks so much better.

LiquidX · 08-07-2012, 08:04 AM

Just use the appropriate sized tap and run it through.

snowborder714 · 08-07-2012, 08:10 AM

What about taking a pick or similar tool and scraping out the plastic from the threads? Or take a propane torch to it and melt out what's left in there.

I have yet to figure out or see anyone who knows what the thread pitch is for the BISS screw. Even if you do figure it out, it'd probably be a fairly odd size which would make finding a tap hard or expensive.

iugrad92turbo · 08-07-2012, 08:15 AM

I stripped mine out, it was scrap at that time so i trashed it.

RvlutionMtrsprt · 08-07-2012, 09:13 PM

The tap is totally obscure, no machine shop I have ever contacted had it. 8x.75 if I remember right. Very expensive too. When the head of the biss screw is stripped I heat up a flat head screw driver with a torch, melt it into the biss screw and let it cool down while holding it in place, then unscrew and remove the biss. Right now, you might be better off melting out the remains. You will also want to replace the shaft seals as you will likely mess them up while melting the biss screw out.

Atuca · 08-07-2012, 09:26 PM

When I got a rebuild kit from you Brian I noticed it came with a plastic screw and not a metal one.

I actually have a metal one in my old TB. What is the difference between the two screws, aside form the obvious material. Is one better at sealing then the other, or have a longer life span perhaps?

To the OP, could you possibly thread a metal one in there to clean threads?

I removed my coolant lines from my TB and did a FIAV bypass; I hope doing that keeps it from ever getting hot enough to melt the plastic one thats in mine atm.

snowborder714 · 08-08-2012, 06:33 AM

They don't sell metal ones any more. I think they actually stopped selling them in the early/mid '90's as the only tb's I've seen them in are 1g's. I have a few in my stash but don't use them. I'm just not sure I trust them. FWIW, I've had the same plastic BISS screw in my throttle body since I rebuilt it at least 3 years ago. No issues with it at all.

You should never have a problem with melting a BISS screw. I've never seen one melted, nor even close to starting. The typical issue I see with them are people stripping out the philips head. You just need to use a proper fitting screwdriver, make sure to push down when adjusting (so the screwdriver seats properly), and turn it slowly.

DSM's 4 life · 08-08-2012, 02:01 PM

Okay problem solved and before people yell at me for "riging it" It does the sme job the biss screw is intened to do I taped the hole for an exaust manifold bolt and put the oring around it it seals tight and will work fine.

tsigreg · 08-08-2012, 05:07 PM

Isn't the biss screw tapered to seal? But hey if it works it works.

mattasi · 08-08-2012, 05:15 PM

Haha if that works then good job man!

LiquidX · 08-08-2012, 05:16 PM

Did you pressure test?

DSM's 4 life · 08-08-2012, 08:09 PM

I will let you know shortly I ordered new 1g tb gaskets from STM usually takes one day for shipping. does gasket matching have a big impact on the intake manifold?

Quote:

Originally Posted by tsigreg

Isn't the biss screw tapered to seal? But hey if it works it works.

It tapers smaller I re-tapped it bigger so it fits in the hole

LiquidX · 08-08-2012, 08:13 PM

If the tb is larger than the intake manifold inlet then port match the manifold to match.

Rsawd95dsm · 08-08-2012, 08:18 PM

Quote:

Originally Posted by snowborder714

What about taking a pick or similar tool and scraping out the plastic from the threads? Or take a propane torch to it and melt out what's left in there.

Thats what I had to do. I used MAP gas tho because it burns hotter and really liqufies that screw lol. Then I took a small pick with a 90 degree bend about 2 MM long and scraped all the residue out of it.

mattasi · 08-20-2012, 12:53 PM

So did your home made Biss screw work?