My custom ported FAST 85/85 - *PICS!*
Thread Starter
Joined: Apr 2006
Posts: 3,909
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From: Grand Rapids, Michigan
My custom ported FAST 85/85 - *PICS!* Well, considering no one wanted to give me any advice on my idea, I went ahead and did my 85/85 intake mod. I recently purchased a 78MM fast from a friend for a really good price but as everyone knows, a 90/90 is better. I don't know about most people here, but I am on a tight budget and $1100 for an intake and throttle body is a bit much. My solution? I bought a polished 85MM Professional Products TB from Byunspeed for $185 shipped. At first I was going to use the adapter plate that came with it, but I realized it would be pointless considering the intake opening was only 78MM and would restrict flow. I then took a set of calipers and measured the FAST intake to find that the inside diameter of the outer O-ring retaining rib was approximately 85MM. I was concerned about sealing the TB to the intake at first, but lucky for me, the 85MM TB comes with a nice gasket to seal the TB to the adapter plate I was not going to be using. It would work perfect to seal the TB to the ported intake. So I started grinding. Took me about 4 hours to actually get it completely shaped right using a carbide burr - I found that sanding drums just melted the plastic and didn't provide a good finish. It came out nicely and I'll have 99% of the performance of a 90/90 for about half the price. I also ported the TB while I had the time, so it should flow pretty close to a 90MM . What do you all think?
Thread Starter
Joined: Apr 2006
Posts: 3,909
Likes: 1,158
From: Grand Rapids, Michigan
Yeah, because the gasket is a flat rubber gasket like they use on carburetors to seal them to the intake. Its no longer an o-ring. I already used a light to check for leakage and there is none. They've used flat style gaskets to seal TBs for years, so I can't imagine it will have any problems.
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Verdad Gallardo Thread Starter
Joined: Apr 2006
Posts: 3,909
Likes: 1,158
From: Grand Rapids, Michigan
It didn't have to be ported, but the lip on the front was a little thick and there was a sharp line where machining was done, so I got rid of that. I also cut the throttle shaft in half. Took all of 5 minutes, so I wouldn't say it really NEEDED any porting. I just chose to make it perform a little better.
i think you're going to run into "slight" vacuum leak problems doing that..
because although the bottom portion of the opening is flat.. the top still has 3 grooves where the old gasket fits into...
unless you plan on cutting up the rubber gasket and gluing it in place where the top grooves still are.. then using a flat gasket for the entire thing.. thats possible..
or epoxying the open grooves up so they are flat like the bottom... might be better
because although the bottom portion of the opening is flat.. the top still has 3 grooves where the old gasket fits into...
unless you plan on cutting up the rubber gasket and gluing it in place where the top grooves still are.. then using a flat gasket for the entire thing.. thats possible..
or epoxying the open grooves up so they are flat like the bottom... might be better
i applaude your efforts and ur intuition but are u sure that the only difference on the 90mm fast is the opening for the tb? only seems that the 90mm top would provide more plenum volume as it was obviously designed to feed a more powerful engine.
Originally Posted by ls2 bait
i applaude your efforts and ur intuition but are u sure that the only difference on the 90mm fast is the opening for the tb? only seems that the 90mm top would provide more plenum volume as it was obviously designed to feed a more powerful engine.
Tech Resident
Joined: Jan 2006
Posts: 5,117
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From: Philly
Originally Posted by Silas2k
thats exactly what i was thinking while reading this... i was thinking the intake runners would be larger or something other than just the opening on the front... can anyone else chime in?
i always figured the intake runners were larger, also, not just the hole in the front...