Tom400CFI

In that example though, wouldn't he have to stick with the Z51 springs for the '90 MY car? B/C if he does, those aren't nearly as stiff as the '84 springs were.

pipeliner1

Matt was in a 93, and is pretty much a freak of a driver. Most championships are in 89's. There is a reason for that.


Your car is illegal for SCCA BS. If you are running SCCA people are being nice.

84 is stiff, but bad gearing, lowest power amount and really bad tire choice kills it.

90 to 95 gained weight and had worse gearing then the 89, but you are correct on changing the springs. Only caveat is that is you want the Z51 springs you must do the whole package. Coolers, rack etc that came in the Z51 package, just doing the springs would be illegal.

Tom400CFI

Tire maybe. Power? I don't agree;
1. It's not a race of HP
2. You can get an 84 to make ~230 hp with the class allowed cat back and free mods.

Whats wrong with a 3.31 gear when combined with the T10 trans? And lastly, the '84 motor has a greater usable rev range than the '85-'91 TPI engine. Tire make hurt it for sure...but I really feel it's a viable option. Can you no longer get a 255/50-16 comp tire?

Did any stock C4 'Vette pull higher "G" or faster slalom than an '84/Z51?

pipeliner1

Crossfire injection, smaller brakes, 275 vs 295/315 and the 84 as the first year model did not have the structural refinement that they added in later years. There is a reason no one has won nationally in a 84.

89-90 have most of the trophies in the closet.

Tom400CFI

Has anyone attempted a serious campaign with an '84?

I feel that the car may have you een dismissed by most -as you are doing- for reasons that aren't meaningful. For example, i do not believe that the Crossfire Injection is a detriment -and that comes from owning one (and auto xing it) for about 12 years. Not meaning to argue...just very curious about this one.

pipeliner1

Im fairly sure it has, and when the 86's came out people jumped to them.

The Cross fire makes less power, it is fact. The brakes are smaller. It has less tire which is huge.

Here is another caveat, they built the car based on a T-Top configuration, not Targa. That means until they actually got a couple of years into the C4 body/frame they did not make the structural enhancements to the car.

If you are having fun running the 84 that's great, but there is a reason the top drivers all look for a 89-90.

Tom400CFI

My CFI carwss an '83 TRANS AM. It was a hoot and did ok. My statments regarding the CFI engine was to point out that which most dont know.

You can get ~230 hp out of a 350 CFI w/o breaking any stock class rules. I know, b/c I have done it and with a 305. That pretty much eliminates any power advantage the TPI has and the CFI still has a larger usable RPM range.

It is hard to imagine that stock early c4 brakes with the addition of good modern pads are not sufficient for auto x duty.

You are right about tire though. The 84 definitely comes up short in that area.

My current car is a stripper '92 LT1 ZF6, 3.45 Gear. Having driven both, I would pick the 84 over my car, but mine is definitely not an 89 or 90.

93Rubie

Correct, they could only be 90 MY springs. As pipeliner1 noted the change over would have to be totally correct.
For example if I wanted Z07 suspension on my 93 FX3 car. I would have to change the springs, front bar, tires, wheels, brakes, lower control arms, and any other part that was available on the 93 Z07 package.

However, good luck finding Z07 lower control arms bushings as they only came on the cars with the Z07 package. NO service replacements and the only ones available now are used ones from a bone yard, if you can even find them. I guess the SCCA feels I'm safer on bone yard parts then, right? I have yet to find a FSK front 92-95 Z07 spring.

The rules are strict in stock class. 89-90 Z51 only is still the best bet.
That being said most of us are NEVER going to be national champions or even regional champions. If you make a few changes to your Corvette but still run stock class, unless someone protests at the local club level, run what you got.

Technically my 93 is not in Stock class as I changed out my front wheels at 17X8.5's for 17X9.5's. That is the ONLY mod that "technically" throws me out of stock. However, I have yet to have anyone complain about it. I should not have to be punished for GM's idiocy to use the smaller wheels. When I bought my C4 I did not even know auto-x existed. Now I'm hooked. Being a butt head about minor rule infractions at the local level will only drive potential SCCA members away. Be smart I mean if it blatantly not even close to stock, ok, but a minor mod or two....come on. If your S2000 that is a good 10-15 years newer cannot beat my C4, the problem is not my very minor mod but your driving.

That being said, my 93 has the exact same suspension setup as a 92, except for the rear sway bar which is 22mm on the 92, and 24mm on my 93. In stock you can now change the front or rear bar. If I had a 92 I would put a 24mm on it to fight the understeer, run my stock 275 tire size and be totally B Stock legal. Funny, my 93 is the exact setup as this modified but still stock legal 92. So why is my car not stock, only model year? That is F-en stupid and NOT logical.

On the flip side Stock classes can run R-Comp DOT rubber what the hell is STOCK about that? I think it should be 140 or higher treadwear rating tires ONLY. I know the new tire class exists now. Thank God, some wisdom at SCCA does exist.

Tom400CFI

Yes, the SCCA rules can be maddening. It used to drive me NUTS that they didn't have a Street Prepared class that "worked" for street cars. My basically F-stock car had to be in E Street Prepared b/c I installed shorty "Headers" (Edelbrok T.E.S. manifolds). What "street car" doesn't have headers?? ESP is a pretty heavily modified class for a "street car", so not much in between F-Stock and ESP. Since I had "no money" back then I was also racing with my regular street tires and plain Auto parts brake pads. CLEARLY, my headers weren't helping anything in a meaningful way, but still put me in ESP where I was running against HEAVILY modified cars. Lame. Still won one event outright up in Idaho and set the FTD...that was pretty cool.

But yeah, the rules can be annoying unless you "live for" SCCA..and I don't. They can be fun events though.

USAsOnlyWay

Thanks for the clarification on Braun, I guess I had it backwards.

SCCA rules are maddening, luckily I only ran stock until the 383 was done. Then it was SSM (SM2) for me. Though of course, now it is only a local car for nationals...oh boy. I think it is crazy that you can do shocks in any class that cost more than a C4 itself!

To the note on HP though, SSM guys are running 600+hp (look at the rwd Rx7s that weight less than C4s too). So I wouldn't say any gains over 230hp aren't valuable.

Tom400CFI

Totally agree about the shocks. That is an interesting point and valid.


That is true. 600+ hp would certainly help you go faster. 230hp vs 205 won't though, in any meaningful way. Especially when the 205hp engine still makes 205hp at 5500 RPM and the 240 hp engine is making 185hp. Especially when the 205hp car can easily (and w/in class rules) be adjusted to make 230 hp -and still have a greater rev range. I should have been more clear, but in the context of this thread (best STOCK C4 for Autox, I was trying to make the point that the false "25 hp" the TPI gets you isn't going to lower your times as much as the super stiff '84 Z51 springs and sways. Whether there is a better C4 or not, it seems that there may be, but my point was that it is not a race of HP as compared to real road tracks and drag track, and choosing a TPI over a CFI for the 25hp would not necessarily be the "no brainer" that it initially appears to be.

Obviously, if you have "600+hp" that is going to help you go somewhat faster...but that ain't stock and is so far out of the realm of this thread, that it's a little ridiculous to comment on. We're talking about 2-300hp stock cars here, and the 300 horse car has nothing on the other two until 4500^RPM.

Anyway, to me, 90's Miata's and Civics are proof that it's a race of maintaining speed through turns, not of HP.

shakedown067

It's either a game of momentum or of torque. Between the CFI, TPI and LT-1, there is only what, 30lb of torque difference. When you are below 60mph and mostly around 30-35, torque is where it's at. Then if you get a lot more torque, you've got to be able to plant all that torque and be able to throttle steer. HP is virtually a non-factor in autocross. The difference between my stock LT-1 engine with chassis improvements, vs a modified LT-4 (400+hp) with stock chassis has pretty much just come down to tires. He has DOT R-compounds and I'm on crappy street tires (for now). I'm pretty confident that if we where on the same tires, we'd be VERY close in times (even though he's clearly the better driver).

93Rubie

I've kinda figured this out too. The small Civics, Miata, etc...have a lot of momentum and lose little in the turns. This is because of how small and maneuverable they are. You can get closer to cones and turn in or out sooner. I have trouble beating a FSP Ford Focus, his car just carries so much speed thru turns it is dumb. We are both on street tires. I may have more grip in steady state turns and can carry a bit more speed but I cannot transition as well and spend more time braking,etc...because I have the torque to reach high straight speeds (in comparison).

Honestly, auto-x is not a Corvettes forte. However, they are a fast and deadly auto-x weapon when driven right. Who says you cannot have both momentum and torque? As always comes down to driver skills.

Planting the torque on exit...heck, I drift more than I turn. So slow, but SO much fun. Trying to get away from that, turning is faster. I would win a drifting competition hands down, however.

I agree on your assessment of the CFI, TPI, LT1/LT4. This is NOT the issue in auto-x. The only limits on the 84-87 would be tire size in stock class only 16 inches wheels=rubber hard to find and NO r-comps. (EDIT: I stand corrected I searched Tire Rack today, good supply of R-Comps less so with street rubber.) That I know of in 255/50/16. A 89-90 Z51 is still the best bet in my book. Closely followed by a 92-95 Z07. Anyone who knows, knows a C4 corners best with as much rubber as you can throw under her.

93Rubie

Not to get too off topic here, but even in STOCK class, you can setup a car so much for auto-x it will be TOTALLY unusable on the street. Ie. Alignment settings. What the heck is stock about 3/16" of toe out?
Oh, well, I try not to worry too much about the rules, takes the fun out of it. I play nice and hope others do as well.

USAsOnlyWay

The point is not ridiculous to comment on, the point is more power is going to be better and get as much as you can! Be it 5 or 30hp when you are talking tenths of a second and starting from scratch why start from behind?

Could the same or similar mods not be done to a TPI motor or LT1 for that matter and put them ahead in power? (And you would have ABS (86+) and better suspension in 88+ zero scrub, and you can make up a lot for spring rate with shock valving...)

A 4+3 with 3.07 stock gears hits 65 at 5k and 70 at 5.5k so really you only need to 5000 RPM for all but the fastest of auto-x courses. So if your operating range is from 2-5k. it doesn't really matter if it faceplants beyond that.

The point of the 600+hp comment is that with C4s specifically, autocrossing at a national level, there is clear evidence that more power is BETTER. So if you are starting from scratch buying a new C4, why start from behind?!

If I was buying a C4 for autocross I would want to be told which car was best, which is what the OP asked for. I'm not saying you can't enjoy or be successful with other C4s (I have an 86!), just answering regarding the best C4.



EDIT: And the C4s dimensions are what they are. We can't make it smaller and we can't make it that much lighter depending on class. Driving a Miata is a much different style than driving a Vette (i.e. just floor it damn near the whole time!). It is all about maximizing momentum with the same principles but the differences in the vehicles requires different styles. All the extra power means that you have to be more accurate in your application to stay right on the edge, but it definitely isn't a game of EITHER momentum or torque. If that is the case, then you need to practice throttle control (trust me, I do too.)

Tom400CFI

No, on the mods to the TPI/LT1. They are already MUCH closer to being optimized in stock form. The CFI comes w/a stock timing spec of 0* and thrives with more timing. A LOT more in my experience. Then there is the fuel pressure which is almost always too low in those cars, as delivered. The stock FPR is adjustable, so no real "mod" there. The problem with CFI engines (and therefore a benefit) is that GM left SO much on the table with them.

The '84 Z51 has a 3:31 rear gear, not a 3.07. I feel the 3.31 is better, no matter then engine.

As for more power is better, in theory, yes, but in practice...only if you can manage it perfectly, and I know of no one who can. I can't. I had my BEST results running my CFI 400/T5/3.45 geared Trans Am in 3rd (yes 3rd) gear for most events. In second, I had plenty of rev range, but just way too much tq/power and engine braking! WAY too much. The day that I set the FTD and beat everyone outright, I ran the whole course in 3rd. Smoother, faster.

Civics, Neons and Miatas prove it; not a race of HP.

The updated front suspension that improved scrub is definitely an strong point. Tire size, and scrub are for sure, great reasons to go for a later car.

shakedown067

They are fast and a deadly auto-x weapon, but MOST of all, they're DAMN FUN. I really can't imagine driving any other car, although I had a blast in my '89 chevy ext cab truck once. Got one run (towed the trailer) and I didn't finish last. Who knew that could make you feel so good, but I felt like I won that day (and two people got beat by a truck with a slipping 200,000 mile automatic transmission)!

Yep...I autocrossed a bagged truck

USAsOnlyWay

I forgot about the G92 option being 3.31s in 84. That makes 5k+ usable.

Still a D36 right? Though with stock power especially on street tires that shouldn't be too big of deal.

In the end, I think we can all agree any c4 will be fun. For the hell of it, I'll try 3rd gear next time I get a fun run.

Tom400CFI

Yep. D36. And yeah, it's plenty strong enough for stock-ish power. I have a bud that has done 100's if not in the 1000's of drag-track passes on his '84. Mid 13 second car with a ported intake, cat back and the aforementioned free tuning.

93Rubie

Dude, that is hard core.

Your right, somehow auto-x with a Miata or Honda might be fun but not sideways torque happy Corvette fun.