I asked: Track it or sell it, you all said track it! Finally ready to run!

[cbaclawski]

Originally Posted by tnova

Count me in on the follow-up on your track day.

I've been prepping my '91 for track days and autocross but keeping it streetable. (For a dedicated track car I have an older Porsche - former PCA Club racer that I've run in TTs and next year in competition). As time goes on I'll likely run the ZR-1 more than the Porsche.

Engine is stock on the bottom with GVD top end porting, Watson headers, RAM dual disc clutch and AL flywheel. 4.10 rear gear also.

The brakes are Wilwood 6-piston calipers with hats and rotors on the front and stock calipers with Wilwood hats and rotors on the rear. Those made a tremendous difference however adjustability, even with a bias valve, wasn't enough. I've recently installed a larger master cylinder ('98-'02 Camaro) since the '90-'91 master cylinder bores are the smallest of the C4s and with the Wilwood pistons more fluid volume was needed.

I absolutely agree with you on brake pads; the right pad can make all the difference in the world. Right now I'm running Wilwood pads that came with the kit, but have had best track experience brake tuning with Hawk pads. The bad part is the Hawk Blues can destroy brake piston rubber components if not cleaned after every event - not something I want on a street car.

Other track mods include urethane bushings and the typical rear suspension changes popularly written about as well as BB C-beam plates

I've also done a throttle pedal mod to improve heel-toe that I'll test out this spring. It changes the pedal pivot point. If it works, I'll publish on the forum or submit for the HTB.

Finally in the process of relocating the battery to the rear passenger smuggler's box combining the Haibeck kit with a SPA 6-pole cutoff switch that keeps factory wiring to the engine area mostly intact. The SPA 6-pole switch prevents engine run-on but protects the alternator though a ground. I'll submit that to HTB soon.

Tnova

Wow sounds like you are going to have a beast! I'll definitely post a follow up to my upcoming track day. I'll try to get some video, GPS data too and will give my impressions on the brakes/pads. I'm interested in your heel/toe mod, as I have an "auto-blip" system installed on my e46(my main track car) which works great, but I'm having to re-learn how to do it myself on the Z - and I was never a pro at it to begin with... I'd install a similar system on this car, but it only works with electronic throttle's so no can do...

Funny/pathetic story about my decision to go to 3.73 on the rear: When I bought the car the seller told me he had changed the rear end to something suitable for the drag strip, I swear he said 4.55. After getting the car home and cleaning it out I found a couple 1/8 mile time slips, so I assumed the 4.55 was still on there. Separately, at idle the tach read about 1200rpm, so I spent many hours searching for a vacuum leak. I never found it, but noticed the butterflies in the throttle body weren't completely closing, so I sent it off to Marc Haibeck for a rebuild. This helped somewhat, though it was still reading a little high but close enough to be within normal parameters. Now, back to the gearing, assuming I'd fixed the leak, I started to pay close attention to the Tach while driving, and based on that, I did the math (speed vs. RPM) I was confident it was a 4.55 rear, which I did not want for road course driving as it would put me in overdrive at track speeds. After some research It was a close call between a 4.09 and 3.73, but based on the layout of the track I go to most (practically exclusively) I decided to go with 3.73. So I shipped the whole car to m Haibeck to do the re-gear. the day after he got it, he called me with some odds and ends that he found wrong with the car, one of them being that the Tach was "comically wrong". Upon hearing this, I asked him to check the gearing, lo and behold the previous owner had re-installed the Lingenfelter 4.09 before selling me the car! Had I known this I would have just kept it as it was and never even sent the car all the way to Chicago for an expensive re-gear! Since it was already there and I had a *slight* preference for the 3.73 vs. 4.09 I had him make the change anyway. In the end it all worked out because Marc found a few other minor issues, removed the secondaries, gave it a new tune, obviously fixed the tach, and tidied up some issues in the engine bay, but between the 2 way shipping of the car, the gearing change and everything else, it was a $6,000 expense/lesson I could have avoided most of if I had just verified the tach. That said, while expensive, it was almost worth it to have a LT5 expert like Marc go over the car, and I did end up with the 3.73 I truly wanted...

tl;dr - I am an idiot...


A couple questions for you:

1) Why did you feel the need to change calipers on the front? So far with the aggressive pads and the stock calipers I can pretty easily lock the wheels/get into the abs at just about any speed if I so choose - at least on the street - haven't been to the track yet...


2) What's the benefit of moving the battery? I've considered replacing the battery with a 40+ lb lighter lithium ion unit, but with no way to corner balance the car I am afraid to throw off the balance. (I did this in my e46 -which is stripped and pretty light - where the battery sits right over the passenger rear tire, That car has an open diff and it was so unbalanced the rear passenger tire would practically come off the ground in a fast right hander and "one wheel peel" with no power to the wheel that had traction... I ended up putting the stock, heavy battery back in...)


***I'm legitimately asking to learn, not questioning your choices***


Curt