I have a 1990 Firebird Formula with a 383 Stroker engine that utilizes Throttle Body Injection. I'm currently running a Holley 2-Barrel TBI unit. However, I am in the process of planning my next upgrade. I am going to switch to the Holley 4-Barrel TBI unit (Holley Performance Products Commander 950 Throttle Body Fuel Injection System 950-21S). My question is what intake manifold would best suit me? It has to be a square flange intake. I'm using Vortec (L31) heads. EGR is NOT an issue. The car is a daily driver that I also take to the track every now and then. The final requirement, and probably the most troublesome, is that I want to be able to use the stock 'PowerBulge' hood. I have searched; but can't find anyone using this combination. I have looked at the Performer RPM intake and have searched the boards for info on it as well. The posts seem to contradict themselves. Some people say that they are using the Performer RPM with no problems using the stock hood. Others say that it impossible. To confuse things even further, a lot of people don't say which stock hood they are using. It is not that I definitely want to use the Performer RPM. It is just the one that I could find the most posts about. If there is something that will do the job better, please tell me. Thank you in advance for any and all of your help!

 

The Holley TB is not as tall as a carb; so the Perf RPM might work.

You might try determining the height of your current setup (intake + TB) from the intake surface of the block, and comparing that to the height of any proposed setup.

I'd also suggest, that rather than that Holley TB with Chrysler injectors which is mostly a POS, you might want to look at this Accel unit. It might be available without the wiring and ECM; or otherwise, it comes from this other comany whose name I can't remember right now, but somebody has posted it before on either the DFI board or the Aftermarket FI board. Do a search for "fuel rails", I believe was what the topic was about, that maybe will locate that link.

 

I have a performer RPM, and quadrajet, with the stock air cleaner, and long stud, using the stock powerbulge hood, and new motor mounts (keeps the motor higher), with no clearance issues. So for what that's worth, I think you have a good chance of it fitting. I have no hood insulation whatsoever though.
Plasticine can help, you can check how much height you have now, then call up whoever, and ask if x manifold is taller than y manifold and by how much. That'd basically give you all you need to know.

 

I just took out an original 305 fitted with a performer RPM and holley 650 dp, I used a drop base air cleaner from weiand and had no clearance problems from the crossfire style hood, I also have a friend here locally that is running the GMPP Vortec dual plane and it clears his stock flat hood great. Hope this helps