Could it be front end lift at 100+ mph?

[tony-muscle]

I am no aero expert or road racing expert, but I am not thinking front end lift would lead to intermittent braking problems. What brake fluid are you running? At the end of a long straight at high speed I would think you would be on the brakes pretty hard. You may be boiling the brake fluid at high temps and if you have not changed the fluid you may have some small water deposits in it vaporizing and causing air bubbles in the lines. You may want to explore changing your brake fluid out to a more race based high temp fluid and flushing the whole system. Just my opinion without much race experience under my belt is my disclaimer.

This is not the issue. I am using Motul 600 plus the outside temps were very cold in the mid 40s. This happened right away when pressing the brakes after the straight away so no chance that the brake fluid was boiling. Hitting the brakes hard after slowing down to 100ish was not an issue.

 

[tony-muscle]

It sounds like you're focused on blocking excess air into the engine compartment, which isn't bad, but long ago when I raced on road tracks, I lowered the rear end 1/2" and the front end 1", and didn't have any problems at 110-120. Yes, you have to be careful of speed bumps, etc. on the street with headers, but that's what worked for me. As mentioned earlier, make sure your strut rods, lower control arms, tie rods, etc. don't have play in them and your wheel bearings are torqued correctly. Little things add up at high speed.

Suspension is tight and there are no bushings. As I said, I check this every time before taking the car to the track. The car as it is, is lowered from stock at least an inch, but probably a little more. I will lower it a little more in combination with the other ideas. It doesn't hurt to limit the amount of air since I don't need that much anyways and it is very easy.
Also, it is possible that I will never have this problem with warmer temperatures since there will be more grip. The lower temperatures I think compounded the issue. At the beginning of the day we were in the lower 40s and then creeped up to the high 40s which makes a big different with grip.

 

[tony-muscle]

A few more pictures.... sorry I am being passed by a Porsche

 

[tony-muscle]

 

[Sheriff41]

Have you considered the brake pad material? Could the high speed affect the heat build up in the pad/rotor combination to cause brake grab? Or could it be the shaking and tire skidding is due to you modulating the brakes as you would at slower speeds when you may need to consider the more rapid heat build up in the brakes, causing more efficient braking? You may need to assess your technique.

 

[Cleveland Crush]

Tony, There are no "inherent" design flaws in our Mustang front ends that need body work changes or re-design for 100mph. Yes that is a lot of track speed, but our cars can handle that without issue. I'd really take another look at suspension geometry and tightness.

A few more pictures.... sorry I am being passed by a Porsche

Did you consider doing a "PIT maneuver" on that Porsche?

 

[Cleveland Crush]

View attachment 68646

You're taking that turn nice!

 

[steves73]

Old picture of what Kar Kraft made for the 71 trans am season, doesn't look stock.

 

[Spike Morelli]

You know, Dodge Daytonas and Plymouth Superbirds had reversed airscoops above the front wheels, on the fenders, to vent any trapped air that might induce lift at speed. Those cars were made for speeds approaching 200 on the high banks. Just an engineering thought. Also, many Bonneville cars will "belly-pan" their cars undersides to lessen the lift effect of under car air. Kilgon was touching on this. Maybe not applicable, nevertheless, an interesting thought.
Photo above kinda looks like the car is "melting". Looks like a top chop on the "A" pillars, and a front end body drop, along with a chin spoiler that has a bend to it. Like a plastic model kit left out in the sun.

 

[tony-muscle]

You know, Dodge Daytonas and Plymouth Superbirds had reversed airscoops above the front wheels, on the fenders, to vent any trapped air that might induce lift at speed. Those cars were made for speeds approaching 200 on the high banks. Just an engineering thought. Also, many Bonneville cars will "belly-pan" their cars undersides to lessen the lift effect of under car air. Kilgon was touching on this. Maybe not applicable, nevertheless, an interesting thought.
Photo above kinda looks like the car is "melting". Looks like a top chop on the "A" pillars, and a front end body drop, along with a chin spoiler that has a bend to it. Like a plastic model kit left out in the sun.

Totally. I already bought the ABS sheet to make a flat belly pan to run from the spoiler back to the oil pan. I have been reading a lot about aerodynamics and they seem to agree that this is a huge improvement to reduce drag and lift. I won't cover the whole under car but from what I read you have a lot to gain by covering up to the front wheels, which is relatively easy to do. In that process I will also add a 1" lip under the current spoiler to lower the amount of air travelling under the car. There are some other more drastic mods like adding those side scoops but although I race the car I still want to keep it looking stock on the exterior. I also drive it around town and to car shows.

 

[KevinP]

Suspension is tight and there are no bushings. As I said, I check this every time before taking the car to the track. The car as it is, is lowered from stock at least an inch, but probably a little more. I will lower it a little more in combination with the other ideas. It doesn't hurt to limit the amount of air since I don't need that much anyways and it is very easy.
Also, it is possible that I will never have this problem with warmer temperatures since there will be more grip. The lower temperatures I think compounded the issue. At the beginning of the day we were in the lower 40s and then creeped up to the high 40s which makes a big different with grip.

This is why they make tires with different compounds.