Originally Posted by xpndbl3

you want to autocross a diesel? first off I doubt it will fit in the engine bay let alone be a good idea even remotely. You'll want a snappy motor, you should be looking to reduce weight as much as possible, not add another 800 pounds to the nose of the car.

Originally Posted by rhit_rs

To be honest, I don't think either one of those engines would be the ideal choice. A potent, torquey small block would be plenty of power depending on how much tire you plan to run. The major advantage of the third-gen over other pony cars is it's relatively light weight. Drop in a diesel or a big block and you're handicapping yourself.

Before you start modifying the car, what class are you wanting to run? Do you want to be competitive in that class, or are you simply wanting to go faster? IMO, there are several other modifications you should make before doing anything to your engine (besides a general tune-up).

1. Get lots of seat time. Driver skill is by far the cheapest improvement you can make, and will make a larger difference than perhaps any modifications you make to the car.

i've done three years and an advanced racing course through Bondurant. right now i've maxed out the car's potential. even Russ Wiles can't seem to get the car any faster (if you don't know the guy, he's like a friggen driving machine. he beat an STi with an Odyssey van)

2. Tires. What are you running now? Depending on what class you are running/plan to run, tires can make more of a difference than any other car modification. Switching to r-compound DOT tires (Hoosier A6, Kumho V710) from street tires is night and day difference and is the easiest way to improve your times. That being said, some suggest staying on street tires regardless of the class, until you want to be competitive. Street tires will help you learn faster since they won't cover up mistakes like race tires tend to do for beginners. Plus street tires are much cheaper

i'd actually like to be competative right now actually, i was looking at 17" fronts (not exactly sure on width yet) and 17"x10" rears wrapped in 275/40-17 front and 345/30-17 rears. Hoosier A6's i've been running on Hoosier Radial GT's for the last two years, and they're finally done.

3. Suspension. A good set of shocks (Koni or Bilstein) also make a large difference especially in transitions. Stiffer springs that lower the car also help handling. I think most competitive 3rd gen auto-x cars are running somewhere between 700-1000 lb/in in the front and 200-300 lb/in in the rear, but I'm not 100% sure on that.

4. Brakes. Before you add power, it's good to be able to slow the car down quickly. At the very least, make sure your stock brake system is in good working condition. Bleed the brakes regularly and flush the system with good, fresh brake fluid. You can piece together relatively cheap brake kits from newer f-bodies and have 12" fronts and 11.5" rear disc brakes that have tons more stopping power than the stock setup. Depending on what class you plan to run, this may or may not be an option.


Give us more feedback on what your auto-xing goals are and we can give you better advice on how to get there.

Another great resource for auto-x info is www.FRRAX.com (F-Body Road Racing and Auto-X forum). There are some real pro's over there that have great advice.

Happy Apexing!

Josh

Originally Posted by auto-x1990RS

over all it's kinda going to become a dual purpose car, auto-x and road racing (track days). the reason i like the Duramax so much is that bottom end torque (peak tq @ 1900rpm) and the fact that it doesn't really drop off till 4500rpm.

Originally Posted by auto-x1990RS

right now, i'm classed as NXF, i wouldn't mind running NXA or possibly RUS.