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99-05 Grand Am




The 1999-2005 Pontiac Grand Am is the most popular of the late model N-body vehicles, and because of this, it is the most common N-body to be modified.  The 99-05 Grand Am came in two main trim levels - GT and SE.  The GT is the top trim level and comes standard with a 3400 V6 and the more aggressive 3.29 final drive ratio version of the 4t45e transmission.  The SE is the base model and can come with either a 4-cylinder engine or the LA1 3400 V6.  Since we currently do not offer any products for the 4 cylinder versions of this vehicle, we will focus on the V6 versions.  The SE V6 came with a more conservative 3.05 final drive ratio 4t45e transmission.  Despite what you may have heard, both GT and SE come with the same identical 3400 V6.  There are differences between some of the years, but for the same year, the engines are exactly the same.  The GT also has rear disc brakes while the SE has rear drums instead.

The LA1 3400 engine (throughout all it's years) is rated at 175 crank hp and 205 ft-lbs of torque.  Some vehicles may claim more than this value, but it is only because they are trying to boost the sales of certain types of cars.  Ironically, the vehicles which claim the highest numbers are also the ones with the more conservative tuning, and the more restrictive exhaust and intake systems.  The engines in these vehicles are nearly identical (for the same year).


Basic Mods

These mods are the best things to start with no matter which direction you go.  In fact these will all even work with a 3500 swap as well.

  • MMS Standard PCM tune - more hp and torque, much better shifting, cooler running engine, more predictable performance, abuse modes and limiters adjusted, get the most out of your engine without sacrificing fuel economy, or even gain economy- 
  • upgraded throttle body (we'll go into this more down below)
  • 180 degree high performance thermostat (ours is a different design than the factory style one)
  • colder spark plugs - optimal heat range depends on mods/hp.  Basic builds get one range colder, gapped at .050 instead of .060".
  • 2.5" downpipe to increase exhaust flow (with or without catalytic converter depending on emission requirements)
  • EGR delete - if you don't have to worry about emission testing


If you've called or e-mailed me asking for advice on a project, the first two questions I always ask are "What kind of a budget are you trying to work with?" and "Do you have any performance goals in mind?"  Budget and performance goals are two major factors which you need to take into account when choosing what I call your "mod path", but they are not the only ones.  After being in business for 18 years, these are the factors which in my opinion determine which Mod Path is right for each customer:

  • Budget
  • Current vehicle condition/mileage
  • Performance goals
  • Use/type of driving
  • Who will be doing the installation/labor?  (DIY vs paid/professional installation)

For the sake of this instructional page, I am going to assume that the use is somewhere between street and street/strip.



I was considering making vehicle condition the first step, but the truth is the budget has to be determined or atleast thought about even before you make decisions based on the vehicle's condition.  This is because at the end of the day, the budget is what determines if the cost to repair or replace parts is more than you're willing to spend.  So what I would recommend is set a budget.  Be realistic, keep in mind that things happen that are unexpected.  You may bring the car in for some work, and they find more work needs to be done, testing the limits of your budget, so plan on it going a little bit above your expected amount. Ifyou're planning on modding over time, or you know you have a personality where you're going to get used to the power you have and get bored, and want more power down the road, it would also be good to think of your budget not as a set in stone constant value, but maybe as a rate you want to spend over time.  One thing that I've noticed customers do is set their budget below the blue-book value of their car.  What you set your budget to is your decision, and yours alone, so you can set it to whatever you want, but I would advise not to think of your car as a financial investment.  As much as we love these cars, they are not collector's items.  So don't think that if you take a $3000 car and put $5k into it that it's now worth $8k.  That's not how it works.  In fact unless you find a buyer who wants all the modifications you've done, these modifications can actually decrease the value to a buyer just looking for a to b transport, in spite of how much money all these mods cost you.  Modding cars (especially these cars) is not a sound financial investment, so don't treat it as such.  Instead treat it for what it is: maybe it's an ego thing  - you want the fastest of that kind of car, or the fastest in your location; maybe you just want to do something different, modding a car no one would expect to be fast; maybe you'd rather have a unique older car that can keep up with a newer car for a lot less money; maybe you just really love the car and you want to keep it forever and make it yours.  Whatever the reason, just be honest with yourself and why you're doing this, and I would just think of whatever budget you decide as an entertainment cost.  Another way to think of it would be to think about what it would cost to buy a new car that would offer the same performance as your older modified car.  At any rate, just keep in mind that "Speed costs, how fast do you want to go?"


Current condition/mileage - when to fix it, and when to swap it


So the next step to get you on the right path, is to actually check out the condition of your current engine. Every 3400 I've ever looked at that hasn't had it's lower intakes gaskets changed before has always shown signs of leakage.  This can be evident by looking at the valley of the engine (between the two cylinder heads).  You're looking for wetness coming from the side of the lower intake gasket between the lower intake and the cylinder head.  This wetness could just be stains around the gasket, or it could actually be puddled up water on the top of the block if the leak is bad enough.  My rule of thumb for a 3400 is if it has leaking intake gaskets, it's ok to replace that and move on, but if it's headgaskets or worse, just do a 3500 swap.  This may sound extreme, but once you commit down the path of fixing the headgaskets/etc, you can end up down a path where you just really don't know what the final cost will be until the engine is completely fixed, and at some point, you can exceed what you would have spent on a 3500 swap, but you're committed and stuck on fixing a higher mileage 3400.  Are the heads flat, do they need milled, do you have them pressure tested to be sure?  Is the block cracked?  There are lots of unknowns on this path and skipping to a 3500 allows you to skip all this stuff for a set price, and get a performance gain in the process.  Even if you fix the headgaskets, replace lifters, etc, the topend at that point is all brand new, but the bottom end is still going to be however many miles were on the engine, and the bearings, pistons, rods, rings, etc will all be higher mileage as well.

So if the engine has intake leaks and not headgasket leaks, you should either do intake gaskets or do a 3500 swap. If you choose to do intake gaskets, it would be smart to do ported intakes at the same time, as well as the Basic Mods listed above.  If you're engine is leaking and has mileage higher than lets say 150-200k, I would really recommend considering just doing a 3500 swap instead of repairing it.  A well-kept enginecan last even as much as 300k or more,but if it's leaking and has issues, swapping to a 30-60k 3500 just makes a whole lot more sense to rewind the clock on your engine's life.


Performance Goals

We all know you guys want your cars to be faster, but how much faster?  Are you doing this for bragging rights?  Maybe you have an exact dyno goal in mind.  Maybe you want to run a certain quarter mile time? Maybe you're out to break some sort of a record for your car.  Maybe your buddy has been talking smack and you want to just leave him in the dust.  No matter what your reasons, it's important to establish some sort of a performance goal when you're modifying your car, and it's equally important that this goal or goals be realistic.


Use/type of driving?

Sounds simple enough, but the answer to this question can highly dictate the way you modify your car.  Most of what we do is "street and strip".  Customer has a car, they want to make it faster, they drive it everyday or most of the time, they want more performance, but they don't want to sacrifice reliability.  The Basic Mods we recommended above all fit into this category, but as you go further, you might find you have to make choices to sacrifice something to get the gain of the modification.  So you should think about not only the type of driving you do, but what compromises you are and are not willing to make.  The engineers who designed you car made many compromises to achieve their goals of making the car perform to the standards of that type of car, be relatively quiet, get a certain fuel economy, not have much vibration, have a smooth running engine that idles smoothly as well, be able to be driven not only across the country, but anywhere in the whole world in any conditions or temperatures and any elevation, etc.  These could be some of their priorities.  When you modify your car, you are changing or re-arranging these priorities.  With these changes in priority will also come changes in the compromises.  You may even be taking those original priorities and turning them into compromises.  The whole idea of modifying a car is to make the car how YOU want it, so at the end of the day, it's your decision what's important to YOU, and what's not.


Who will be doing the installation/labor?

Why does this matter?  Well part of that answer is about the total cost of the modification as labor is a big chunk of the modification process, and could cost quite a bit depending on the extent of the modifications you have in mind.  In fact if you're paying to have each and every mod installed, another factor that comes into play is grouping the mods into packages to be installed at the same time instead of one piece at a time, so you can save the overlapping labor costs.  If you're planning on installing the parts yourself, this can also be an important factor because you don't wsnt to bite off more than you can chew, so if you are a novice, you may want to stick to the easy to install mods, and either not do the more difficult ones or pay someone else to install them.  Also keep in mind, not all shops are created equal, so as much as you might think that any shop can do any job, do your homework and make sure they aren't going above their abilities either.