A quick Google search will yield countless results about trying to use TBI headers on a Vortec engine. About half of them say it is possible and about half say it will never work.
As you may already know, Vortec shorty headers are almost double the price of TBI headers. In addition to this, you will find that there are almost no longtube Vortec headers on the market. The closest you can find are mid length headers, and they are a small fortune as well.
However, for those who have a 96-98 Vortec 350, still want the performance of longtubes, but have a limited budget, there IS hope!
Before we begin, you should familiarize yourself with the differences between the TBI and Vortec engines. Obviously, the headers and fuel injection systems are different. We are only concerned about the exhaust differences though. The primary difference is that TBI engines have an internal EGR valve and utilize some sort of SMOG pump. The Vortec engines have an external EGR tube that connects to the stock manifolds then runs back up to the intake. Other smaller differences are in the 02 sensors. The TBI engines have 1 Pre-cat 02 sensor while the Vortecs have 2.
Another thing that is handy to know is that Vortec engines have 2 sets of 02 sensors. The first set (before your cats) control your A/F ratio and are needed to have the engine function correctly. The last set (post cat) is ONLY to check the efficiency of your cats. You will need to have this set tuned out since you will not be running an EGR tube and thus will NOT meet emissions.
- Again, please note that this is NOT for a truck that will undergo emissions testing. If you are sly, you can pass a visual test. But because you are deleting the EGR tube, you will not be able to pass emissions if they actually check you.
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Here is what you'll need:
* TBI longtube header of your choice. Just make sure they are not SMOG headers.
- Here is what I used:
http://www.summitracing.com/parts/HOK-2462HKR/
* EGR block off plug
- Here is what I used:
http://www.summitracing.com/parts/NAL-12556596/
* Some tune to get rid of the rear set of 02 sensors (post cat) and EGR tube. You can achieving this by either using a high end diagnostic tool to set the 02 and EGR values to '0'. However, a better route is to have a professional tuner go ahead and tune your PCM for you, and erase these values while he is in there.
- Here is the company I used:
http://www.blackbearperformance.com/
* Lastly, I would take this chance to upgrade to new cats. If your truck has 100K+ miles on it, chances on your stock cats have seen better days. I know mine had. Some may chose to cut off your stock cats, but I chose to upgrade mine for a variety of reasons.
- Here is what I used:
http://www.summitracing.com/parts/MPE-53006
* I am assuming you already have some type of aftermarket muffler. If not, you should upgrade that as well to take advantage of the increased flow of the new headers.
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Now, assuming you have purchased all the parts listed above, you will need to get an 02 bung welded onto your right side header.
Here is what I mean:
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Above is the header from the left side. It is the only one that includes a bung for the 02 seeing as TBI engines have only 1 pre-cat 02. You will need to have an identical one welded onto the right side to accommodate for your 2 02 sensors on your Vortec.
The only other issue you will have to deal with is getting a CASE learn. If you chose to get a PCM tune like I did, when you install it, your SES light will be on. This is because your PCM and your crank position sensor will not be sync'd correctly. This will cause your PCM to read multiple misfires. To fix this, you will need someone with a GM Tech II. You will probably have to take it to your dealer, and they will probably charge you close to $100 to get the simple procedure done. It sucks, but there isn't a way around it.
And there you have it! Longtubes on your Vortech engine. Enjoy your increased performance and sound.
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Here are some before/afters of my truck:
Before:
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After:
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Drivers side 02
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Passanger side 02 that was welded
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Here is a sound clip. It came out poorly though. My turn downs kind of blasted the camera. The truck sounds much quieter than in the clip. I will try to make a better one later.
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