Still not sure what failed but I did find this in service manual which is a bit concerning.
View attachment 1420
- Vacuum line is intact and doesn't leak with a vacuum pump.
- Vacuum line didn't collapse with the pressure my hand pump could create.
- Check valve(didn't know this existed) seems to work. Holds pressure on one end and lets air through the other.
- Master-vac holds pressure. Haven't gotten this apart yet.
- Calipers aren't seized.
- Brake pads look healthy. Lots of life left no chunking/glazing. Pads were new for the session and calipers were new(O'reilly's rebuilt) for the weekend.
- Pulled the seat and there's no tools or anything that could've blocked the pedal. Lied down in the car and mucked with the pedal and couldn't get it to bind or anything.
Not related to the failure but turns out the Z originally had a light that would warn you if the difference between the brake pressure in the front and rear was too great. Kinda of interesting.
Engine compression on cylinders 3 & 4 is low. 80psi and 145psi vs 150-175 on the rest of the cylinders. Added oil to cylinder 3 and redid the compression test and the pressure stayed the same so maybe it's the head gasket or the head was warped by the fire. Retorqued the head and readjusted the valves on cylinder 3 hoping for a miracle but no.
Mr. Hedges, it is so good that you were unhurt. Fire is the single most feared threat for racers. Fortunately I have never had to endure a fiery crash. It does look like your car launched quite high, before taking the tumbles. A nasty wreck, to be sure.
In the first couple of seasons I ran my Z boiling brake fluid was something that troubled me greatly, especially at Westwood. I would get about 10 minutes into a race and have the pedal go soft. I found that I would need to gently pump the brakes with my left foot before getting into the braking zone. I also found that if I didn't get them pumped up enough the pedal would be on the floor before I had slowed the car down enough to make the turn in.
This always resulted in agricultural racing, grass mowing and gravel collecting.
After many different configurations of air ducting and master cylinder replacements I found the perfect setup that gives the car brakes that last the entire weekend without the need to bleed them after every track session, a pedal that is hard, and there first time, every time.
I also eliminated the vacuum booster, and installed a dual master cylinder setup with and adjustable balance bar.
Another issue I found was the motor mounts failing. Brand new mounts fresh from the local Nissan dealer would separate after one weekend of running hard. I ultimately fabricated solid mounts, which solved that problem. If solid mounts are not permitted in your class perhaps a simple chain limiter could be used to keep the engine relatively close to the mount when it fails.
I see that you are running ITS, and as I am unfamiliar with the prep rules for that class I don't know if you can make those types of changes to the brakes and engine mounts, but it would be worth looking into.
As others have commented, a switch operated by the engine oil pressure to kill the fuel pump(s) is essential for safety in the event of a crash. When I got my Z in 1989 it had been a Conference race car for 10 years. The car had been run with a bolt in roll bar (simple hoop, nothing else) the stock fuel tank, and had nothing to ensure safety. I completely rebuilt the car, stripping it to the bare shell. A full cage was added, as well as a fuel cell, with multiple pumps, a surge tank, and the oil pressure cut off switch.
I also added a battery disconnect. At the time the location was recommended to be as close as possible the the battery with the shortest possible run between the positive terminal and the switch. Since the battery on a Z is at the right rear corner of the engine bay I mounted the switch in the center of the inspection door directly above the battery. This leaves only about 10 inches of cable energized after the circuit has been opened. In the more than 20 years of racing since and several off course excursions there never has been a problem for turn workers getting to it to shut the power off.
I know in your situation with the wind carrying the flames across that side of the car the switch would have been impossible to reach, and seeing the video has given me ideas for a remote activation location, like with a cable, from the left side of the car. Hopefully, should the need ever arise, then the power could be shut off from either side of the car.