I am trying to produce a cold air kit. Clearance is a big issue. From the 7.4L TBI unit to passanger side next to air conditioner compressor then to area to passanger side of radiator. Clearance is 2.90 inch at compressir lines so I need to use a 2.5 inch tube. Question is can a 2.50 inch ID tube flow sufficient air to feed 350 CID at 5800 rpms?

I would try a dual 2.5" wherever you can fit it.

63mm (OD so even worse) is pretty small for your engine.

That was my concern. I will check my MAP readings with the one outlet at 2.5 inch. If I have to will go with a dual snorkel. Issue is the other side the alternator is in the way.

can you section the tube so that it's more of an oval? get the bend right, then cut it down the middle and add some flat stock to make it oval?

The hood on vette has a support member running front to back of hood that would require a "V" notch in 12 inches of tubing running back to front just to R of AC compressor. the alum tube comes in 6 inch lenghts(Spectre) with rubber like connectors. Would take some serious welding skills to joint 12 inch of pipe but-but with notch.

Ideally a TPI air filter. But I found out the radiator shroud needs to be replaced and also the 1985 hood is different that 1984.

I was thinkin oval top to bottom, not side to side. If thats what you meant, then eww....thats a sucky problem....

seems like the tpi air cleaner retrofit would be cleanest, but i guess it's alot of work to swap the shroud and possible hood problems....hmm...

Did mine with some 3" aluminized exhaust and radiator hoses for the bends. First one was with a cone style K&N filter, then had some left over parts for a paxton used that to come out of the throttlebody to turn around towards the firewall and made a box for my cowl hood Its all in pieces now but if you wanted an idea I could take some pics. I see this thread is 2-3 months old so you may have already figured it out, if so it would be interesting to see how you made it work, I may be re-doing mine since Im working on it now.

actually it may come together in a couple weeks. It appears 3 inch will fit! When I close hood it will compress alum tube and coupler a tad. 4 inch high blower bonnet to a 3 inch pipe with reducer. then 22 deg elbow downward to straight pipe to another 22 deg and the AC sits front of and below AC compressor behind radiator passsanger side. Used KN beer can shaped AC. Issue was the provider of parts on ebay was a disaster to work with. Steer clear of engine_store.

Don't know how relevant this is for you but the air cleaner intake in my car has an oval shape with an area equivalent to a 4" tube, and that's for a 305 meant to rev to 5000.

Also be sure the rubber components are rated to decent temperature.
The "black" reducers from 4" to 3" that are avilable for plumbing are not a good choice. They will soften at 150* F and will change shape/collapse as you drive.
The expensive stuff (500* silicone, multi-layered) is the way to go if the budget allows.

The home supply store plumbing material was not intended for engine bay temperatures. Plumbing rubber, PCV, etc is great for "quick" projects, but will not be reliable.
This is the best place I have found for Clampco T-bolts and silicone hose at very reasonable prices. Shipping was free and extremely fast.

http://siliconestop.com/

I bought Spectre company connectors for cold air automotive use. Not sure if they handle boost however.

Silicone connectors are also a bad choice. Out-gassing will poison the O2 sensor(s). Radiator hose pieces/sections work. May need to move up to truck sizes.

RBob.