How much can you over bore a GSR TB? I was told you can only over bore the back that attaches to the IM 4mm. Is that right? Im going to have my dad bore out a TB for me at his work. If i bore the back to 64mm does the plate inside have to be 64mm or is it alittle less?
Matt

 

i believe max. for stock tb is 64mm. you should have it done proffesionally since they change the butterfly along with the boring.

 

My dad would be able to do it because he is a tool and die worker and does alot of stuff that involves precise measurements. I just want to make sure im doing it right before i ahve him work on it. I was just wondering if the valve is alittle smaller or if its the same size as the bore.

 

4 mm overbore so yes, 64mm with a GSR tb. I guess it should be slightly smaller so it won't jam but you have to remember the butterfly sits on an angle so you have to get that right.

 

ya good luck on that project..let us know how it goes

 

Well this morning my dad found a thick piece of brass at his work and he milled it down to the stock TB valve thickness. He said that the brass he used was 4x thicker than what it is now. Its a nice tight fit and opens and closed easily. The valve has 3 thousands clearance from the TB. Tomorrow i might put it on my car and adjust the tps sensor for it, but here are some pics of it finished. It is a GSR TB bored to 64mm to match my skunk2 IM for my del sol.

 

Nice work, you should get a hold of some of that coating that they put so no air leaks