I've got a 92 rs, tbi with a Performance Products spread bore intake manifold and wanted to put Summits 14"x3" air filter on it pn SUM-239431. Are there any clearance issues or should I go with a 2"?

 

Forgot to add is does have a 1/2" tbi spacer

 

It's difficult to say without knowing the manifold carb pad height. That said, my Edelbrock RPM Air Gap, which is about as tall a dual plane intake that there is, fit under my IROC steel hood and Z28 fibreglass hood but there was trimming needed in each case. The air filter lid shape makes a difference here as well.
I can't say if your manifold is as tall as the Air Gap but the 1/2" spacer is going to make it very close.
You're running TBI ? At least with a 2" filter element, you don't have the issue that those with carbs do. And that's the filter lid being too close to the choke horn. It kills airflow.
So, to answer your question: With a 3" element...yes, there probably will be clearance issues.

 

I know a 2" will work, I just thought a 3" would let more volume in.

 

It certainly would. A K&N filter allows more air over a traditional paper element as well so if you feel compromised with the 2" paper filter you could always make the move to K&N.
David Vizard has published results on how much filter is needed based on HP/CFM requirements. I don't have the exact info at the moment however I believe the 3" is good to over 400 HP. It'll feed more than that of course but after that threshold, it becomes a restriction and becomes a question of power lost.

 

I am going too use that Summit one.

 

My bet is that there'll be contact with the frame under the hood. I figured someone else might have tried this exact arrangement (TBI with an open element air filter case) but I guess not.
Worst case is, if you don't want to trim as I did, you'll have to pick up a separate 2" element. You don't have to deal with the choke horn clearance which is the case with a carb.

 

if you still have that goofy spacer that goes between the throttle body and air cleaner, just get rid of that and gain an inch and a half of clearance and open up a ton of airflow...

but in all honesty, the stock air cleaner is plenty big for about 300hp, a little more if you take that stupid inner ring that sits right inside the filter out of it. you also get the benefit of cool air getting fed to the engine, which is worth a bit of power and economy.

 

A 3" filter will let a lot more of that hot, thin, low pressure underhood air into the TBI than a 2" filter. Ever consider using ducting and sourcing colder, more dense air from out front instead of under the hood?

 

For what it's worth, K & N rates their 14 x 3 filter at 790 cfm and their 14 x 2 at 525 cfm.
This doesn't apply to a typical paper element. Just K & N.

 

Nova, If I take that spacer out are you saying that'll provide enough clearance for me to get a 3" in there?