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I got to battle it out in the Holley LS Fest Track challenge! And I answered my question about the Z28.
It was a separate challenge at the LS Fest using the west course of NCM. There were loose rules that put us into 3 classes, Stock(200TW tires), street prepared(200TW tires), and race car(slicks). The Event was held Friday+Saturday.
Dropped the car off tuesday to get a rim straightened, and aligned. They couldn't find the rim they'd claimed was bent when they mounted the new tires, so Thursday morning I got the car back aligned with only -1* camber again due to some confusion between the service writer and the tech. So they had the car 24 hours, and did nothing to it. That left me with 6 hours till departure, and I had to install Z51 corvette rear calipers(smaller piston), new pads front and rear, and the hoosier hubs.
Not to mention interior and sound deadening so the car could run in the street prep class.
This is what the car looked like at 10:30AM about 30 min after I got it home.
And this is what it looked like at 2pm when I headed to work
I left work late, the car made it 6 hours before an air bubble caused it to overheat at about 1:30AM. I pulled off the freeway and used water from some industrial park sprinklers, and got back on the road. Of course it overheated again 30min later, so I got a hotel 40min south of NCM. Got up at 6am, and with the engine cool I topped of the radiator, and had no more overheating problems for the rest of the weekend.
The new RE71R's were surprisingly good on the street. Definitely more comfortable and quiet than the R888's in the same 285/30-18 size. Easily 100 times better in the rain too.
The hoosier hubs and smaller rear calipers didn't eliminate the pad knockback entirely, but it's very close to completly gone, Even running RE71R's.
You know the CTS-V calipers are doing work when they turn gold
The weather forecast was pretty bad, which is my only guess as to why half the cars didn't show up. I'm not complaining because that meant there were only 2 run groups and we were going 15min on 15min off all day long. It was brutal on the cars and drivers due to the 90+ heat but a blast.
The first session the new tires felt terrible, but I managed the fastest time by the smallest of margins.
I ran a 1:43.150 and a new Z28 on some nitto invos ran a 1:43.263.
The next session the new tires got a lot better and I ran a 1:40.09 the Z28 slowed down to a 1:44.1
The next two sessions I did a 1:39.5 and 1:39.2 and I discovered that the RE71R's are a pure qualifying/autocross tire. If I did my usual "drive the wheels off of it from green to checker" my opening flying lap was usually 1.5-2 sec a lap faster than the rest of the 15 min session.
I took a session off due to a check engine light, the Z28 owner came over and said "really, 1:39's? you must be making a lot more power than me."
I don't think he believed me that it was a stock LS1 long block with 115K+ miles.
The Z owner decided to put his Trofeo R's(illegal because they're 60 tread wear) on the Z28 and cut a 1:38.588. Tires really do make all the difference.
At the same time the track manager decided to show us all how it's done and he went out in the track owned C5 Z06 with michelin pilot super sports on it, and he ran a 1:38.498.
While messing with the tune(knock sensor failed), it was pointed out that my undertray was ripped on the left side, and was flapping in the breeze and dragging on the ground.
With the undertray removed and a plan for how to manage the tires, I took it very easy on the warmup lap and set a 1:37.816 on my first flier. I usually get a good rhythm going and set my fastest lap on the 3rd or 4th flying lap, but these tires just don't allow that.
The dragging undertray had definitely been hurting the car on the straights, I picked up about 4-5mph.
With the fastest time of the day I headed to the hotel, and hoped that no faster cars showed up Saturday.
Saturday morning a few more cars showed up, but nothing serious. The first lap of the morning session I ran an ugly 1.37.110, and I broke the diff breather with some violent wheel hop and spent the rest of the day trying to patch the car back together.
The best part about trackdays is all the cool people you meet while trying to fix your car. 4 different people(all camaro/firebird folks) helped me fix the car including the Z28 owner.
After failing to get the diff sealed up well enough that it would not drip fluid on track, one of the guys that helped out loaned me his 1998 formula with the new Strano coilovers, and some really old low grip firestone tires for one session. I was afraid the car would be twitchy with the low grip tires on it, but you can see me shaking my head during the video because I can't believe how easy the car is to drive. The taller tires also eliminated the 3-4 shift on the front straight, and kept me well off the limiter in the couple places where I was banging it in my car. I just wished I'd had more time in it, but some lightning moved in and they shut down the track for the day.
Overall a great time, and I got an insane amount of seat time for 250$.
I not only won the street class and 500$, but I also set a faster lap than any of the race prepped cars managed. Like I said, the RE71R is one hell of a fast tire for one lap.
It's really interesting to me that the poll shows the same response of the Z28 Owner. (you need more power to be turning those lap times)
I ran the math on it, and My car weighing 3220lbs with a 10.3in tire, and the Z28 weighing 3880lbs with a 11.3in tire(that's for the trofeo R the nitto is even narrower).
My car carries 78lbs per inch of rubber. HP/Weight= 8.05
The Z28 carries 86lbs per inch of rubber. HP/Weight=7.65lb/hp
The Z28 has a 5% power advantage, but the old F-body has a 10% tire advantage.
If you figure that the tires buy you time everywhere on track, whereas power only buys you time when you're flat to the floor, it was a no brainer.
The poor Z28 never stood a chance.
Thanks to everyone for the encouragement.
I'm still working on the project, the firebird is fully prepped with new brakes, and the diff breather hopefully fixed, just waiting for the next barber date in November.
Here is what I'm working on this week though.
My buddy Adam (the guy who owned the Boss 302 for the nurburgring series) totally screwed me over on the track batter we'd been planning for the last couple months between my C5 Z06 and his Boss 302.
That's an interesting way to do your harness shoulder straps. I figured that would be illegal. I assume the mount point is too far behind the seat and would stretch.
Any idea how much that changes the front wheel offset? (the new wheel bearings, not the KW's)
It doesn't. The adapters make the thinner SKF Xtracker bearings "thicker" so that the rotor stays in the same place and the brakes fit the car properly.
Originally Posted by smitty2919
That's an interesting way to do your harness shoulder straps. I figured that would be illegal. I assume the mount point is too far behind the seat and would stretch.
I just finished a custom bar for my car:
On top of the distance concerns mentioned above....
In a real crash, I predict a dangerous failure of that harness bar. The two sets of legs aren't very far apart so there isn't much actual triangulation. On top of that the heim jointed bars are bolted to the sheet metal brackets that hold the seat bottoms. They are mostly hollow underneath (I've cut them out of a couple cars over the years, they are nothing I'd mount safety gear to). In a crash, it will likely pull that roll cage tubing forward, jamming the heim jointed bars down into the sheet metal they are sitting on before swinging forward enough to be extremely bad for your health.
I would refab it to be restrained by the rear seatbelt mounts like the old LG Motorsports harness bar, or at least use a bracket from that rear seatbelt mount (the top/shoulder harness mount) to restrain that tubing from coming forward. The support would be considerably stronger in tension than compression. You only have to compress it enough to have it buckle, but you have to stretch it enough to tear it in half.
It doesn't. The adapters make the thinner SKF Xtracker bearings "thicker" so that the rotor stays in the same place and the brakes fit the car properly.
On top of the distance concerns mentioned above....
In a real crash, I predict a dangerous failure of that harness bar. The two sets of legs aren't very far apart so there isn't much actual triangulation. On top of that the heim jointed bars are bolted to the sheet metal brackets that hold the seat bottoms. They are mostly hollow underneath (I've cut them out of a couple cars over the years, they are nothing I'd mount safety gear to). In a crash, it will likely pull that roll cage tubing forward, jamming the heim jointed bars down into the sheet metal they are sitting on before swinging forward enough to be extremely bad for your health.
I would refab it to be restrained by the rear seatbelt mounts like the old LG Motorsports harness bar, or at least use a bracket from that rear seatbelt mount (the top/shoulder harness mount) to restrain that tubing from coming forward. The support would be considerably stronger in tension than compression. You only have to compress it enough to have it buckle, but you have to stretch it enough to tear it in half.
Be safe!
I appreciate the response. I only use the car for local autocross, no road racing. A friend of mine did have the idea to tie into the body in the area of the rear shocks. Run a bolt though the body and place a nut from the wheel well area much like you mentioned about it needing to tear apart in tension. I can still do this down the line.
This was the old harness bar from angle iron and roll cage material. It bolted into the rear seat lower seat belt locations. The new one is a step in the right direction getting the shoulder strap angle better.
Last edited by smitty2919; 10-11-2016 at 07:24 PM.
That hood extractor, is that for heat or to help prevent the car from floating at high speeds?
I got a spare hood with a motor I just bought and some $10 hood vents at the swap meet, I plan on experimenting with it but mainly to keep under hood temps down in the summer.
That hood extractor, is that for heat or to help prevent the car from floating at high speeds?
I got a spare hood with a motor I just bought and some $10 hood vents at the swap meet, I plan on experimenting with it but mainly to keep under hood temps down in the summer.
Thanks!
The hood extractors are because the hood was lifting up so much in the middle that the edges of the hood were pinching between the fenders at speeds above 120mph.
The flaps on the hood are for cooling. I'll get around to detailing the aero development in a video soon.
Congratulations man love all your stuff.
Not sure why you can only get -1 degrees of camber. I used to run my koni shocks on the lower perch with the eibach prokit and ran -2.5 The guy setting it up said it wasn't even maxed. Since then I went back to the higher perch and -1.5 due to more street driving.
Did you massage the pedals at all? Heel/Toe is hard in these cars.
09-12-2016, 01:08 PM
I actually won something! 
