LS1Formulation

iTrader: (13)

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?

jmm98LS1

iTrader: (28)

Very nice! What's the gasket look like that's gonna seal the tb?

2000WS6TA

iTrader: (5)

looks good, but can you grind into the space where the rubber seal supposed to go without it leaking?

LS1Formulation

iTrader: (13)

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.

onefastss223

iTrader: (14)

Very nice!

JunkyardZ

iTrader: (7)

Looks good, should perform right up there with a 90/90.

Finding ways to cut cost and increase power is always fun.

LS1Formulation

iTrader: (13)

Yeah, low buck is where it's at. I'll have this car in the 11's for under 12K including the purchase price of the car.

lgobraves

iTrader: (14)

that looks good...The throttle body needed to be ported right out of the box??? thats kinda disappointing if that is the case

LS1Formulation

iTrader: (13)

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.

GR33N GoblinM6

iTrader: (14)

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

LS1Formulation

iTrader: (13)

I already was thinking ahead on that. I cut the stock gasket and stuck it in the original grooves up top. Worked like a charm!

lastcall190

iTrader: (36)

Wow... very resourceful, nicely done!

-J

Ace$nyper

iTrader: (8)

That's very clever, always good to see an off the beaten path idea come out so well!

ls2 bait

iTrader: (11)

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.

LS1Formulation

iTrader: (13)

Yes, the only difference is the throttle body opening. Otherwise they are identical.

Specialized

iTrader: (15)

Can someone else verify this statement? If so, I think I'll be ordering myself up a 78mm FAST sometime soon.

01 BERGER CAMARO SS

iTrader: (77)

Nice!!!

Silas2k

iTrader: (5)

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?

LS1IMPULSE

iTrader: (42)

anyone know the F.A.S.T reps sign on name? Send him a PM to this thread and we will find the answer.

ChocoTaco369

this is what i was thinking, too. no way FAST could charge hundreds more simply for a hole that's 12mm larger. technically, the 90mm would be cheaper to produce as it requires 12mm less material i always figured the intake runners were larger, also, not just the hole in the front...