So I found my vacuum leak since I put on the new head and S2 Ultra intake, its the bypass for the IACV on the throttle body. The opening on the manifold is 74mm and I'm using a GSR tb Maxbore opened up to 64mm. Well, the inlet on the IM is large enough the gasket won't seal and allowing vacuum to pass by. I looked at a spare Omni 68mm I have for a friends build and it still has that bypass, but not sure if it will be wide enough to seal rather. Any thoughts on an affordable 68mm tb I can get that will work?

 

You mean the fitv ? Why don't you want to use a 74 mm tb and matching gasket? You have the manifold at least take advantage of the bore.

 

Really don't need one that big. This isn't a monster build, just a GSR with pr3 pistons and mild cams.

 

I would highly sugest the Pro seies manifold for your aplication with a nice port and polish i bet you would benifit more from that manifold, The ultra street manifold is more beter suited for a higher comp with biger cams and a better flowing or ported head. Not to say you couldnt use it its your probally not going to ever use its full potential if your not going to even match the throtle inlet.

 

Yeah, that is what I noticed too, inlet is too large for smaller throttlebodies. Here is 60mm, just for example.




So I used adapterplate and I can port it what size ever I want.




Unfinished but ready.

 

That's awesome. It crossed my mind to do that but I don't have access (or skill set) to tools to make a plate.

 

That adapter what I posted is made and finished by my friend (working in aluminium foundry), but this is doable using just a basic tools (pillar drill, power drill if you have steady hand, file, dremel or similar). If you use aluminium plate thats surface quality is good enough, there isn't even need for re-surface it.

Material measurements for base are 4"x4" and approximate 0.4" thick (it's not flex so much). Then draw outlines on it by using tb-gasket and the rest is just a drilling and filing.

 

I just ordered a larger throttle body. Probably overkill, but it was on the list later anywho. I'd still like to make an adapter plate and see what kind of differences the 64mm to 70mm does on a dyno when I finally make it to one.