How to Begin Mods to Your 3800 Powered Car

Posted by Alex Darmos on

Questions to ask:

  • Can you do complex installs yourself?
  • How much do you want to spend?
  • Will you continue to upgrade your car in the future?
  • Do you have a factory warranty?


For every person with a Series II 3800, the SC pulley swap should be the first thing considered. It offers the largest HP/dollar value of any mod. You will need a special tool to do the install which can be bought or rented. Install time is about 1 hour. If this is the only mod you plan on doing, then the 3.5″ pulley should be used. The stock belt can usually be used but we recommend the 4060658 belt or our oversized tensioner pulley. The 3.5″ pulley swap will give you about 20 additional HP.  2004+ Grand Prix (Series III) supercharged cars will require colder thermostatcolder spark plugs, cold air intake, TB spacer, and bolt in ZZP downpipe and that will just allow you to run a 3.6″ pulley.

Series II – If you plan on doing other modifications as well, then the 3.4″ pulley is a better choice. It requires a smaller belt or an oversized tensioner pulley. The 3.4 will give about 25 additional HP. Supporting mods that are required include: colder thermostat, stage 1 throttle body, colder spark plugs, cold air intake, and a TB spacer. We recommend at minimum, installing the Ubend delete, but the best exhaust mod is our downpipe.  For additional exhaust flow, you could look into our stainless Power log.

Available octane plays a part as well. If you live in a state with only 91 octane available, you will need to do additional mods to run a 3.4″ pulley without KR. You might want to consider the 3.5” pulley. If you live in Indiana or parts of the country with 94 or 95 octane available, it will be very easy to run the 3.4” pulley without KR. Keep in mind that a larger pulley with no KR will make more HP than a smaller pulley with less timing (more KR).

If you plan on continuing to mod your 3800 in the future, then you should buy our modular pulley system. The assembly is lighter than a press on but more importantly, it will make future pulley swaps easy without needing to use the puller tool again. Then as you mod your car, you can buy smaller pulleys. This will allow you to run one size pulley for the street and one for the track, or when using race gas.

After, or along with the pulley, you should run a colder thermostat and colder spark plugs. The 160 is the best choice but doesn’t work very well in winter operation. You can switch back to stock for winter use or buy the 180 and use it year round (99+ cars should use a 180° thermostat to prevent CELs, unless running our ZZP 1.0 PCM).

For a colder spark plug, we recommend the NGK TR6 or TR6ix. These plugs will help to lower KR. New plugs will also increase the performance and gas mileage of a car with used plugs. Many people run TR55’s but we have found no ill effects of running TR6’s, and they work better for getting rid of KR.

If you have a 97 or 98 then a CAI is a very good choice as your next mod. If you have a 99 or newer your air-box is a little better, and you can postpone doing a cold air intake if you install a drop in K&N filter. The ZZP 3800 cold air intake will give excellent gains and help reduce the KR that you will most likely be getting from running the smaller pulley.

Exhaust should be considered at this point. The bolt in downpipe should be your first part of the exhaust to upgrade, followed by removing the resonator. After that you can replace your front exhaust manifold with our Power log, and next would be a ported rear manifold (discontinued- checkout our ZZP Rear Power Log). The factory mufflers are not restrictive and should be changed based on looks/weight/sound before all else. Once you’re making over 300WHP, then we can talk about the performance aspect of a cat-back exhaust. The U-bend and/or resonator should cost $50-100 to be replaced by a local exhaust shop. You’ll want to pick up an Osimulator if you are planning on eliminating your rear Osensor, and yes, this stuff is all emissions legal as you are not messing with the operation of the cat. Exhaust work is an excellent way to get rid of KR when running smaller pulleys.

Easy mods from here include a water pump under-drive pulley, and a throttle body spacer. The Spacer will help get rid of KR, the WP UD pulley will free up a few top end HP. Both are inexpensive ways to continue the pursuit of more HP.

The ZZP PCM is an excellent mod at this point. It will help lower KR, and make driving the car a much more pleasurable experience. It increases HP, changes shift points as well as fueling, makes the car shift harder under Perf shift mode, takes away your top speed limiter, raises your rev limiter and has a few other tweaks. It will lower your gas mileage slightly and increase the chance of tranny failure (due to firmer shifts) but at your HP level, you shouldn’t have to worry about the transmission yet.

At some point above, you are going to want to consider Poly Motor Mounts and a shift kit. The shift kit, in combination with the PCM, can break hard parts in the transmission, so that is something to be aware of especially if you have heavier rims/tires/brake rotors than stock.

You are now done with the easy stuff that most people do. From here you need to decide how far you’re going to take your car. This will help you make the decision between high ratio rockers, and an after-market camshaft. If you plan on being faster than mid 13’s or make more than 280 crank HP, you’re going to need to do one of three mods: rockers, intercooler, or Cam. Rockers add about 25HP, increase gas mileage, do not change reliability of the car, cannot be seen by the dealer, are relatively easy to install yourself, and will support low 13’s without an intercooler. They help the engine flow better, lowering KR and allow a drop in pulley size by about .1.

Combined with an intercooler many users have taken a 3800 with stock camshaft, rockers and an intercooler deep into the 12’s with close to 300WHP. Bang for the buck rockers are an awesome mod.