3.5 THDP turbo match

Just thought I would pass this on.

I pulled my 3.5 THDP and noticed it did not match up to the turbo exact by the carbon deposits, see attached picture.

I am running a GT 67 turbo.

Would I be right in assuming that this would effect my flow out of the turbo and be a restriction?

I am going to mill this out to match. Will this be a benifit or wasting time?



  • turbo and Down pipe 002.jpg
    turbo and Down pipe 002.jpg
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Nothing wrong with a 3.5 on a p trim. I am using a 3" on a q trim. I just took a die grinder to mine and matched it to the turbine housing to eliminate any turbulence.

Yes I have heard that a 3" is all I need, but that is what was on the car when I got it.

Ill make Her work!

Who knows, I may go bigger turbo in the future?

tbirdv6 said:
If you re-tool the pipe you can get it to fit but orginally never was intended by application

I don't inderstand how this contributes to his question since he would have the same situation with a 3".
That's hot rodding. Sometimes you can or have to mess with stuff to get it to work to it's full potential. You can't really go too big on a DP, and a 3.5 ain't gonna hurt performance, be it a P or Q.

Just match it to the housing so you don't have to worry if you are losing flow or not.
Your 3.5"TH downpipe was originally made for a p trim turbo, you need to grind down the edge of the dp to make it match.
Make a template of your turbo outlet and then trace the edge on the dp, this will tell you how far you need to go.
Warning, stainless is a p.i.t.a. to grind, be preparred to wear heavy gloves and eye protection because the bits will stick in your skin.