91 emissions

[aajj1987]

my friends 5.0 has alot of emissions equipment on it. do i just start at the smog pump and keep ripping it off or what? any advice would be helpful. any do's and dont's. appreciate the advice yall.

[five7kid]

Don't mess with anything that you don't understand what it does.

Which 305 is this, the LB9 (TPI) or LO3 (TBI)? Taking the A.I.R. system off can affect the calibration of TPI.

A lot of people do it anyway, but the truth is the system doesn't cost any power beyond what it takes to move around its 3 lbs or so weight - cleaning the trash out of the interior will have more of an effect. Taking A.I.R. off is more hassle than the benefits derived. The EGR can be removed, but then you'll get SES lights and it also doesn't detract from performance. Of course there's the cat. Everything else is part of the feedback control system and needs to stay.

The simple truth is the mantra of the benefits of removing "smog crap" is more pipe dream than anything else. The real benefits come from spending your time and money where it will make a difference - exhaust upgrades, cam upgrade, head improvement, PROM tuning.

[aajj1987]

the emissions equipment i want to take off is on a tbi unit. i heard you can rip everything off and gain some horsepower. i was wondering if there is any adverse effects i need to worry about. and no smog testing isnt done here.

[five7kid]

It's simply not true. There is nothing to "rip off" to gain power.

Okay, TBI - that's good to know. Understand this is a speed density system, so drastic changes will affect the parameters assumed for the computer tuning.

Step 1 - Unless you do this, don't count on anything else helping. Replace every piece of exhaust on this car. Start by removing the exhaust manifolds and y-pipe, replace with shorty headers and y-pipe. My personal favorites are the Hooker 2055HKR - you can find cheaper, you can find more expensive, but you won't find better. Then, the tiny 2-1/4" cat has to go - a Catco 9118 is a direct-fit for the Hooker headers. After that, take your pick of any cat-back system for '86-'91 TPI single cat application Camaro/Firebird. I know, I know, yours is a '91 and not TPI, just trust me on this. I'd recommend replacing all of this at the same time. It'll run you about $1000 if you do the installation yourself.

Step 2 - The single snorkel air cleaner is restrictive. Either find another air cleaner like it and graft a 2nd snorkel onto it; go open element (not my first choice); or a set-up from ramairbox.com. You need to transfer the inlet air temperature sensor if you go with anything other than your stock air cleaner. You could do this first, it's certainly less expensive than the exhaust, but will help performance a little bit even if you don't do anything else.

Step 3 - Cam. The stock LO3 cam is lame. This is where you'll probably get to the point that the stock PROM tuning won't handle it, but something like a Comp XR260-ish cam will really wake it up. You will need new aftermarket valve springs - factory or factory replacement springs won't cut it. You have a roller cam - I'd suggest getting a roller cam to replace it even though they are more expensive. You can reuse your original roller lifters. If you go with a cheaper flat tappet cam, you'll have to get lifters and all new pushrods - that will end up nearly as much as the roller cam itself, and the flat tappets are simply inferior to roller lifters.

Step 4 - Heads. The LO3 has the infamous "swirlport" heads. Fine for what the factory did, terrible if you want to improve performance. The two most popular alternatives are TPI heads, casting # 081, or World Products S/R Torquer 305 heads. The World heads have 1.94"/1.50" valves, but typically need some port clean-up to get the most out of them. The 081 heads will have 1.84"/1.50" valves, putting in 1.94" intake valves is pretty simple for most machine shops, and they also benefit from some port clean-up. Figure on all new valve springs to support the aftermarket cam.

After all that, you could consider an intake and throttle body upgrade. The 350 TBI has larger injectors, easily found at junkyards. Edelbrock makes a Performer TBI manifold. Other people use a carb intake with a TBI adapter. What you do there is up to you.

Now, that was a lot more than what you asked. But, expecting performance gains from ripping stuff off is nonsense. This stuff here is real-world.