Ok so I have an 87 IROC that came factory with a 305 auto and small rear gears. Since then pretty much everything has been changed. It now has a 350 ZZ4 with a comp 480 cam, T5 trans out of a 91 iroc and 3.73 rear gears. The motor still has the factory TPI setup and I feel like something just isnt adding up. It feels like with everything that has been done i should have a solid baseline to build a pretty bad street machine. But for some reason it just doesnt seem to make as much power as youd think it would. Im just asking for some help, guidence, suggestions, whatever. Thanks

 

Switch to a HSR, or miniram. Or port the crap out of the tpi stuff. That tpi is killing your performance.

What is the actual cam specs for that cam?

You probably need a tune too....

 

Ok i shouldve added that i bought the car with all of that done to it minus the rear swap. i just did that. And i had someone make me a tune and when i installed it the car ran like complete crap. And to be honest i dont know what you mean by an HSR or miniram

 

Here's an article from Super Rod that test some different intake systems including Holley Stealth Ram (HSR) and TPIS Miniram.
http://xtremecarzone.com.au/index.php?showtopic=386

Your original TPI is to restrictive for your engine.

I have a similar setup as you have since 1992 and I use TPIS Big Mouth Manifold, TPIS Large Tube Runners, Ported Plenum to match runners and TB (easy to do) and 52mm Throttle Body. This setup will be better for mid range torque. The TPIS Miniram or HSR will be better in high end HP.

 

Do yourself a favor and search "hsr" on this site. There are a great many people that have switched intakes for minimal fuss and have gotten great results. You can find a hsr, complete with rails and injectors here for around 600 or so. It is a bargan. It will wake up your motor so much. You will need to get a new tune though, because you would be changing a major part. It IS WORTH IT!

 

The ZZ4 crate engine has stock aluminum corvette heads on it that were designed in the early 80's. Performance wise, they could be called boat anchors but since they are aluminum, that term almost doesnt fit properly..

As these guys above said, you are choking a nicely built engine with a cool looking but very poorly designed intake manifold. The air has to travel about 2 feet from throttle body to intake valve. A modern higher rpm setup appreciates an intake length in the 10"-15".

Goodluck, having it tuned properly is very important.

 

Ok thanks a lot. If anyone has a link to where I can find a good intake I would greatly appreciate it.

 

Your best bet is to post in the parts wanted section here, or browse the pays for sale. It is likely that you can find a complete stealth ram, with injectors and an adjustable fuel pressure regulator for between 450-700 bucks. If you have the wiring and ecm for the tpi it is pretty straight forward. There are hundreds of threads on the HSR. The info is out there.

Oh, and if you have the extra cash, pick up some heads. Profiler makes some real nice heads for the money (1150 to your door, set up for a roller cam with decent springs).
AFR if you have the budget.

Some sportsman 2 heads or some iron dart heads are not too bad for what you have, but why not pay another couple hundred and get some nice quality aluminum heads.

If the budget just isn't there yet though, pick up a hsr, and give her a good tune. It will feel, and drive like a whole new car.

 

You have a strong engine. A carb would get that performance out of it and CHEAP! Carbs are simple and you cant argue with performance even though a lot of folks on here like fuel injection. Im also a big fan of fuel injection if its working properly. In modified engines F.I. can be a freaking nightmare.