Since there are a couple threads recently started and the questions pop up from time to time, here's an autocross 101 primer as it relates to third generation F Bodies:

Stock
F-Stock: All ’82-’92 V8 F-Bodies and Turbo Trans Ams.
G-Stock: All non-turbo V6 F-Bodies.
H-Stock: Iron Duke F-Bodies.

You can’t mix-and-match options between model years. In other words, if you have an ’85 Z28, you can’t run 1LE stuff or swap motors, intakes, etc., from another year. You do have options of using whatever could be had for that model of car for that year as long it was available from the factory that year. Mostly as it applies to thirdgens, gearing options and perhaps converting a car into a 1LE or WS6 clone (but must be configured with every option) if it was available that year.

Modifications allowed: Shocks, front sway bar, exhaust from the cat back, air filter (anything that fits in the stock airbox). General maintenance stuff like brake pads and rotors, plugs, wires, distributor cap and rotor, coil are open, too. For tires, any DOT-legal tire, including R-compounds like Hoosier and Kumho, that fit on OEM-sized rim. Any wheel can be used but it MUST be same width and diameter as stock and +/- ¼” of the OEM offset.

Paul and Lynne Kozlak's famous F-Stock '89 IROC 1LE:


E Street Prepared
All the ’82-’92 V8 and non-turbo V6 F-Bodies are “on the same line” so you can mix and match options – commonly called “update/backdate” -- between the model years as long as it’s just a bolt-in affair that requires no machining. My car is a perfect example as it’s an ’82 Z28 but has an L98, rear end and front brakes from later thirdgens. You can start off with a V6 car and swap in a V8 as long as it’s from an F-Body produced between ’82 and ’92. It must be the entire engine/heads assembly, though. You can't, for example, pick a cam from one year, heads from another year, and block from another year.

You can also use any transmission available from ’82-’92.

The Turbo Trans Am is listed separately from all the NA cars, which means it’s kind of hosed since there aren’t any update/backdate possibilities, and it’s also stuck with the 200R4 auto tranny.

Modifications allowed: Everything in Stock plus headers, intake from the manifold to the airbox, ignition and fuel delivery (such as swapping from carb’ed to FI, bigger injectors, ECM upgrades including stand-alone systems, etc), wheels (flared and/or cut fenders are OK to accommodate larger wheels), rear sway bar, springs, panhard bar, torque arm, SFCs (attach to no more than 3 points), clutch, flywheel, pullies, differential, bushings, front race seats, brake calipers as long as they attach to the OEM mounting points, brake rotors, lightweight battery, relocating the battery. Brake calipers (and rotors) can also be changed as long as it's a bolt-in replacement, i.e. no machining or redrilling to mount them (backing plates can be removed) Emissions stuff doesn’t need to be retained.

Anything inside the engine must be stock or OEM replacement, so no upgrading cams, rockers, etc.

Four-cylinder F-Bodies are in F Street Prepared.

Mark Madarash's multi-time ESP National Championship Firebird:


Street Modified
This is basically a class that allows motor and transmission swaps as long as the engine is from the same manufacturer as the vehicle such as swapping an LSX into a thirdgen. As far as I can tell, just about any engine modification is allowed. Cams, cranks, rockers, stroking, whatever. There’s some limited body work and aero stuff allowed. A little more liberal suspension modifications than Street Prepapred, but must retain stock attachment points (my take is that the main difference is spherical bearings can be used while in SP you're limited to non-metal bushings). All the Street Prepared modifications are allowed, too.

There's a minimum weight for the class -- 1800 lbs + 200 lbs per liter for RWD cars (weighed without driver). For turbo or supercharged cars, add 1.4L to the engine's actual displacement.

Street Modified fourth gen:


Street Touring (ST), Street Touring Unlimited (STU) and Street Touring Extreme (STX)
These are kind of like Street Prepared-lite classes where R-compounds are not allowed -- tires with a treadwear rating of 140 and higher are required. The classes are really stringent on retaining all the emissions, so catalytic converters, EGR, AIR, etc, must be retained. You can install headers but still must retain a catalytic converter. All Stock modifications are allowed plus sway bars, springs, bushings, differential, torque arm, panhard bar, bolt-in SFCs, air intake from the throttle body forward, headers, ECU reprogramming, front race seats, battery. In STX and STU, you can change the brake calipers as long as they are just bolt-in -- no machining or redrilling

ST is limited to 3.1L displacement, 225mm tires and 7.5"-wide wheels.
STX is limited to 5.0L, 265 tires, and 8"-wide wheels.
STU is limited to 5.7L and 285 tires. Wheel width is unlimited.

My old STX LB9 Firebird:


Also, an interesting read, a guy on the west coast, Jason Rhoades, is building a '67 (!) 302 Camaro to run in STX. Jason doesn't half-*** anything, so check it out if you want to see what effort some people put into building cars to race around in parking lots.

C Prepared
Does your car breathe fire? This is the class for you. Admittedly, I don’t know much about what’s all allowed in CP having never run anything beyond Stock and Street-whatever classes. Cliff notes version from what I can tell is buy a pony car, build a killer engine, strip the interior, use real slicks and go curb-stomp baby seals.

C Prepared thirdgen:


Maybe somebody who has a CP car can elaborate?

Link to PDF of 2011 SCCA Solo Rules.

Pat

 

subscribed

 

Great thread Idea!
forced induction is legal in SM though.

 

Oh yeah, I forgot about that. There's a weight calculation:

So by my fuzzy math, minimum weight for a Camaro with a 5.7 and FI would be 3220? (7.1*200 + 1800)

Pat

 

Thanks!

 

Awsome post. I'm going to be giving this a try this year. Do I need interior for SM?

 

reply fail

 

A little write up I did on prepping my old Nissan Sentra SE-R for F Street Prepared:

http://straightpipemagazine.com/archives/675

The car was moved from DSP to FSP two years ago and on the same line as the 1.6L Sentra/NX from 1991-1994. There are more update/backdate options in ESP for thirdgen F-Bodies, but it still gives an idea on what to look for when trying to maximize the rules.

Pat

 

Hey, i'm looking to prep a '92 GTA for autocross, and I've been having alot of trouble working out some details. Don't really want to splurge for R-compound tires until I have more experience under my belt, but finding a good, low treadwear (looking for under 200) tire to fit the stock 16's is proving to be difficult. but after seeing this post I looked at some 265/45/16 kuhmo's with 180 treadwear and those are looking perfect for the STX class (i personally hate being in classes that allow r-compound when i don't have them, so i've been looking at street touring for a while).

what I want to know is where did you get your info on 265 width being allowed in stx? this and one other site says that, but every scca rulebook i look at says 245 is the max for stx. if 245 is max width then i'm stuck with higher treadwear again I really hope your are correct, but i'm trying to confirm your source. I don't want to be in STU because it is a 305 car, and likely will be for a while, just don't think it can hold its own in STU, but could prove to be competitive in STX if i can get these tires.

if 245 is the max, anyone know of some good (sub 200 treadwear) street tires i could run on the car, i'm just not finding anything below the 300 mark, currently using 340 treadwear bfg g-force summers, and they leave a little to be desired.

 

The 245 size tire limit is only for all wheel drive cars.
But the limit for two wheel drive cars in stx is 265.

Copied from the rulebook.
B. Tires may have section widths up to and including the following:
ST, STS, STR (AWD) – 225 mm
STX (AWD), STU (AWD) – 245 mm
STR (2WD) – 255 mm
STX (2WD) – 265 mm
STU (2WD) – 285 mm

 

I believe that blue Camaro belongs to Brad and Liz Foreman.

In C Prepared, the car must remain stock-appearing, but otherwise, allowed modifications are pretty open. The engine must be production-based, meaning that you can run pretty much any GM engine that came in a F-Body. You _cannot_ run an aftermarket block, however. The cars' weight is determined by such things as engine displacement and wheel width:

V8 engines greater than 5100cc 3000
V8 engines equal to or less than 5100cc 2700
6-cyl engines maximum 4500cc 2450
Turbocharged 6-cyl engines maximum 4500cc 2550
Turbocharged 4-cyl engines 2450
Maximum weight on the rear of the car shall be 51% of the total
weight of the car. Exceptions to this rule: Corvair, Yenko Stinger

Cars running wheel widths greater than 10" must add 50# to the above weight. Max wheel width is 12". There also appears in the rules a max wheel diameter of 16", but this was supposed to be phased out. I'm not certain where we stand with this phasing-out program, but the rules list wheels greater than 16" incur a 50# penalty.

Most C Prepared cars are dedicated race cars. Their interiors are gutted, windows have been removed, and/or replaced with Lexan, all accessories have been removed, and the cars usually run on slicks. The class is a ton of fun, and the competitors are some of the most helpful people at the event.

Gene Beaird,
Pearland, Texas

 

hell yea this is what im aiming for

 

Awesome post, this is sticky material. I guess I've always misread the update/backdate rule to say that the engine and transmission had to be updated/backdated together therefore ruling out a 350/t5 combo (since it was not a factory configuration.) Did they edit that rule since 2010?

 

Engine and trans are separate. For example Mark Madarash's '88 GTA is a 350 (built to Firehawk specs) with a T5, and my car is an '82 with an L98 and T10.

Pat

 

where do you autocross at?

 

Usually FedEx Field with the SCCA's D.C. Region and Blue Crabs/Regency Furniture Stadium in Waldorf with Autocrossers, Inc. D.C. Region is done for the year but A.I. has a autocrosses on Sept. 18, Oct. 9 and Oct. 23.

Pat

 

double post

 

Awesome write up; I found it really helpful.

Question, how do you know about Mark's firehawk spec L98? I can't find single solid spec on this motor; no cam profile, no head casting number or specs. I'm trying to massage my car into ESP legality and I'd like to max out everything I can within the rule set.

 

Casey's gonna love seeing a pic of his 4th gen killing cones on a public forum

 

He got the documentation from SLP. And whatever documentation SLP had on the motor has since burned up in a fire.

There was a guy either here or on the frrax.com forum who built one a few years ago. Said he was using magazine articles as a guideline.

Pat

 

That sucks that the specs are gone. Someone's gotta know. And another point were do torque arm relocation brackets like UMI's put you class wise? And what and the traclink since it adds a mounting point?

 

SLP cam used in the firehawk is a 214/224 with a 115 lsa, .470/.490

I'm not too positive on the rule but i believe the subframe connectors cannot tie into the UMI crossmember. And i'm not sure about the track link; the rules say you may add or replace a torque arm.

 

As long as this thread got revived, does anyone know what classes weight jacks are allowed in? Probably trying to set up my car for STU. Thanks!

 

Weight jacks are legal for STU, ESP, SM and CP.

Pat