Intake & Exhaust
There are two parameters of an intake which you should consider. Flow and temperature. You want the least restrictive intake deliver the coldest possible air to your turbo. The stock intake is a pretty restrictive one, but can pick up quite cold air. The first step could be to remove the stock airbox and put a direct filter on the end of the crossover pipe. While you can get rid of some of the restrictions this way, you will get considerably higher intake temperatures at your intake.
On the other hand you can easily break the end of your pipe, because there is no simple way to secure the cone filter.
Pls keep in mind, that this is a gel battery, you shouldn't put a normal one into the cab like this. Also you can see a little plug lying on the console. It's a plug which comes standart with some kind of welding machines, could handle some 120 A current or so. I'm using this plug to disconnect the battery's negative cable when leaving the truck alone for a while.
The next step could be to provide some fresh air to the filter. There are a few ways to do this. A few guys just simply remove their passenger side headligh while racing. Others cut a hole into the fender or into the fenderwell. I've not decided which way I will choose, yet.
Even with the cobra you probably won't be able to use your heater core port on your radiator any more. So either you will have to live without a heater core or you will need to change something around your radiator. You can buy after market radiator with different heater core outlet position (big bucks involved), or get a different end tank for your stock radiator. Some Vette end tanks said to do the trick. I've removed my whole heater core system, with the plumbing, so I don't know the details here.
Installation of a blow of valve (BOV) in a vehicle equipped with an automatic transmission is not that critical, but it's sill a cheap insurance to protect your turbos. Most manual transmission turbo cars came with them from the factory, however SyTy's haven't.
Anyway, to mount any of the BOV, you have to weld the flange, tipically comming with it, to the intake between your TB and Turbo. I'd say the closer to the turbo the better. With the stock IC, the only option is to get a metal turbo-to-IC pipe and mount it there.
First of all you shouldn't expect big gains (if any) with TB upgrades. Especially if you are using the stock IC. It's a lot bigger bottle neck with it's 2" inlet than our twin 48 mm TB. Anyway if you have a high end build, or just have to replace your TB for some reason (I had to, because of bad leaking at the shaft ends), there are ways to upgrade it. GM used the same TB in a lot of different applications, but with different linkage. However if you don't want to hack around the linkage you have to stick with the 89-92 305/350 ci TPI TB's (I need clarification on this one, older TPI and LT1 won't work for sure). You can get after market TB's from a lot of vendors, like Accel, Holley, BBK/Edelbrock, typically in two sizes, with 52 or 58 mm blades. BBK/Edelbrock even produced/advertised TB's specifically for SyTy's. I bought their 58 mm unit (PN #1551). Looks good but I can't see any performance gain coming with it.
Anyway, pls also keep in mind that our intake ports for the TB have a 52 mm diameter. So if you go with the 58 mm unit, you will have to port your intake up. Also a few words about the throttle body airfoils. They will do nothing fancy in our application (or in any force induction one BTW). They won't hurt, but that's all.
Quite a popular and effective mod. EGR stands for Exhaust Gas Recirculation and was designed to decrease nitrogen oxides in the exhaust emission. It introduces exhaust gas back into the intake manifold. The exhaust gas doesn't help combustion but occupy volume, reducing the total amount of useful mixture of air/fuel. The operation is controlled by the ECM with a vacuum solenoid to control an EGR valve mounted on the intake. There are two main reasons for disabling EGR. First it will dramatically reduce your intake temperatures, second it will increase the amount of useful mixture which burns in the cylinders. It will also help you to keep you intake much cleaner after you get rid off the carbon deposits created by EGR.
The above way has one problem if you are using stock or L35 heads. The hot exhaust gas still could go till your cover heating the intake. To prevent this you can JB weld the EGR passage in your lower intake shut. If you are using Vortec heads, that's not an issue there. I'm planning to do this welding in the future and will include some pictures then.
The Stock exhaust has a 2.5" downpipe with a cat connected to it. After the cat there is a 'Y' pipe and two 2 " (?) pipes with two mufflers. It was that way when I got the truck, but was in a really bad shape, so I removed everything after the cat and fabricated a 2.5" single pipe with a Bontex muffler. Never again. Bontex didn't let me watch their work and they had a good reason for it. I guess they had no 2.5" muffler around, or just want to spare some money and welded in a 2" muffler. Well it was quite for sure... I realized that when looking for additional tenth's I decided to go to 3" and removed the old stuff. Anyway, I was searching for several weeks but couldn't find anybody who could bend such a diameter pipe. Finally I asked for the help of my Dad and J.Bandi, bought some 90 degree knees and a few meters of pipe, all SS and MIG welded the whole stuff together. It came out really nice. Big thanks Bandi!!! The best exhaust which I've seen so far for these trucks...
It was done as a prototype, we performed plenty of the weldings under the truck. As you can see it has no muffler, but still has a cat. The cat is an universal Catco 3" unit from Summit. Before the cat we welded up a M18x1.5 mm nut for the wide band O2 sensor. It would be better placed on the downpipe a bit nearer to the turbo, but it works that way too. Since I keeped the stock down pipe so far, the 3" had been narrowed down and sliced up to be able to connect to the down pipe with a exhaust clamp.
With the open pipe the truck became much more louder than efore, but it's still far to be the loudest car out there. I can live with this. Here comes an other shot showing the almost perfect the weldings.
An other exhaust releated modification is the wrapped down pipe. I'm using 2x50" wrap from DEI, which is enough to cover three down pipes. The wrapping makes no good for the down pipe, but could lower your intake temps. It prevents he upper IC from getting all the radiated heat comming from down pipe. You can also see my AutoMeter pyrometer mounted into the down pipe on the next picture.
