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The 3500 ports are SMALLER on the LIM than a 3400. A while back I made the mistake of slightly widening the 3400 UIM before even looking at the 3500 LIM and had to port it out quit a bit to match. Luckily I didn't go crazy on the UIM.
As for the gasket, you should be able to trim it up a bit. You can line it up to your TB with the bolts and press against the edge and that gives u a line to follow. Or if you have the throttle plate out you could probably mate it to the UIM on a bench and carefully go around with a knife to cut off what sticks into the opening.
Fixed my post but you got it right. I'm not sure how far off the measurement is , but after seeing the difference in size I compared it to the 3400 LIM I noticed the difference. If you don't want to go crazy with porting you can bevel the edge and just blend it down a bit. As long as the air doesn't hit a sharp obstruction it should flow alright.
When I opened mine up I used some cardboard (have also used left over gasket material that comes in a sheet for around $6, seems to form better) lined it up to the UIM, and pushed a screwdriver through where the bolts go and dropped the bolts in place. I pressed down along the edges of the ports to see the outline and cut it open with a razor. Then I went to the LIM and put down a couple strips of duct tape. Lined up the cardboard and carefully traced it into the tape with a razor. The duct tape is a life saver in case u slip while porting because it catches the file or burr before the mating surface gets damaged. Once you have your outline u can bevel the edge back at a rough 45* and then decide how much effort you want to put in to blending it down.
I looked back briefly and saw your LIM looks like it is not ported. If your UIM is not ported then you probably don't have much material to remove. I think the reason the 3500 ports start out smaller is because the way the 3500 UIM is larger inside without runners, then gets sucked down the smaller port it increases velocity.
Yeah I don't want to port it so much but rather make the intakes uniform so flow isn't compromised. Either way I'm sure the setup I end up with will be twice as good as my old 3.4 intakes. Those things are a joke.
93 Firebird 3.4
Pacesetter Headers, Flowmaster 80, Comp 1.6 RR,Cloyes 2x Set, P&P Heads & Intakes, Custom Cam, Holley FPR, Ram Air Intake, Posi Rear w/3.42's & Disk Brakes. Cam and Heads by 60Inclusive.com
"It's your car. Do with it what you wish, but as you enter this unknown world you will need to invent the wheel all over again. For the adventurous and those that are backyard mechanics who have nothing but time you might like this. Most have plenty of frustrating moments and the process usually takes significantly longer then what anyone could imagine. The end result of this conversion is completely up to you." - Jon McCullough of BMCautos.com
I took the time yesterday to grind off the letters/numbers from the top of the 3400 upper intake. I also dropped it off at a friends house to have it slightly ported/smoothed to match my 59mm TB. Once he's done with it I can clean it, paint it, bolt up the TB/egr block off plate, and get some pics for you guys.
Should look good, especially with the black powdercoated tb, and stainless steel bolts.
93 Firebird 3.4
Pacesetter Headers, Flowmaster 80, Comp 1.6 RR,Cloyes 2x Set, P&P Heads & Intakes, Custom Cam, Holley FPR, Ram Air Intake, Posi Rear w/3.42's & Disk Brakes. Cam and Heads by 60Inclusive.com
"It's your car. Do with it what you wish, but as you enter this unknown world you will need to invent the wheel all over again. For the adventurous and those that are backyard mechanics who have nothing but time you might like this. Most have plenty of frustrating moments and the process usually takes significantly longer then what anyone could imagine. The end result of this conversion is completely up to you." - Jon McCullough of BMCautos.com
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