Drag Week 2012 - Project GIRTST 71 Mustang (get it right the second time)

[STINEY]

Everything tucks in nicely. I am going to swap the calipers to the front mounting position to make a bit more room and its necessary when using the six piston brakes for road course.

That's a very neat shock relocation fab deal you did there.

One question for my uninformed mind......why is it necessary to move the calipers to the front for road course?

[Bob Holmes]

Found the NACA paper, just forgot to bring it to work. I'll see if I can get it done tomorrow.

[SuperBuickGuy]

Nice stuff.

[CDMBill]

That's a very neat shock relocation fab deal you did there.

One question for my uninformed mind......why is it necessary to move the calipers to the front for road course?

Yeah, I wasn't really clear about that. I run three different brake set-ups, one for street, one for Drag Week and True Street and one for road course auto-x events.

The rear drag race brake is the new one from Baer that easily clears 15" wheels like the Convo-pros or Billet Specialties I have for the two sizes of Drag Radials 325/50's and 315/60's. I had the rears on for Drag Week '11 but I forgot the hubs and didn't get the fronts on the car. Their is a pretty big weight difference between the six piston 14" rotors and the four psiton 11.5" rotor set-up.



The six piston stuff looks like this. And while it clears the new shock location it'll be easier to service the shocks and the brakes if they are mounted in front of the axle instead of behind it. And, it moves a little bit of weight towards the middle of the car, maybe good for turns on a polar moment basis and likely unimportant for the drags as its unsprung weight.

For the road course and auto-x stuff I swap the rear-end for a 4.11 pumpkin with a 31 spline Detroit True trac carrier instead of the 35 Spline locker set-up I have for the Drags. The locker is a bit of a PITA on corner exits and is really fun on tight auto-x courses. Given that the caliper swap is quick and easy using Earl's speed bleeders. I keep the calipers sealed up full of fluid with little brass plugs for the lines so bleeding is five minutes.

The fronts I usually leave on for street and road course are the six piston calipers and big rotors, but I'm trying everything to reduce weight for Drag Week especially off the nose of the car and the smaller front set-up will take 12# off each side of the front suspension. Same goes for the wheel and tire combo. The welds with the M7H fornt runners weight 32# a side less than the 18x9 Borbets with the 275/40/18s in the front.



Its a bit of a pain but I decided to drive on the street tires at Drag Week this year as I don't want to kill the fornt rims and If it rains I can just roll along. I did two really wet Drag Weeks on the Drag radials and while we survived it made for some interesting moments.



I've done consulting work with Baer Brakes for many uears and I get a deal in case you think I'm nuts with the brakes, which I am.

[dieselgeek]

I know what I would do with EFI, 1000hp, and a need to keep it cool. Get with Dieselgeek and set it up for E85.

Treed ya! The downer is that these guys can't get E85 anywhere except in 5 gallon jugs sold at ripoff race fuel prices. Bill and Brian would absolutely love what E85 would do not only for cooling but for torque gains. We proved that in Doc McEntire's 68 Camaro at Drag Week this year, Pro Street N/A winner. He had a highly optimized Gasoline tune on his Edelbrock EFI system, spent good time on the chassis dyno in prior years - this year, we did a quick EMS swap, did a "drive it on the street" E85 tune - nowhere near optimized - and the car ran consistently quicker and faster on the E85. We're going to spend some time actually tuning it this year, also gonna set up JeffMcKC's car for e85 at the same time. It's perfect fuel for these street/strip cars, and with the ability to flip a switch and run gasoline in a pinch (where e85 isn't available)... things work out. But again, in SoCal and NorCal e85 just isn't available.

[Bob Holmes]

Bill, is there any plating attached to the new shock mount? Or is it welded straight to sheet metal? I see the plating under and on the side of the rollcage attachement point, any for the shockmount?

[CDMBill]

Part of the reason the tube portion is as long as it is is that it catches the vertical side of the frame rail and the vertical side of the admittedly thin wheel tub. The mount intersects a minimum of two layers of metal in all directions and is tied off above and below the flat surface so I decided not to add additional plate beyond the portion of the roll cage plate. The wide flange on top allowed me to tie it in torsion across that portion of the wheel well which is doubled at that point and the notch catches the convertible reinforcement box at the front.

Do you think it needs more?

[Bob Holmes]

Can you cycle the suspension and check to see if the sheet metal is flexing?

We plated the stock rear shock mount on the roadracing car. You have some very high frequency pulsations in a shock. I think you might be subject to a fatique failure. But, I really am not sure based on your statement that you tied it into the frame rail. If it was only attached to the sheet metal I'm seeing in the pictures, I'd be very concerned.

[SuperBuickGuy]

Do you think it needs more?

Yes, at both the shock mount and where the spring attaches to the frame.

[JeffMcKC]

Bill whats the chances of cutting that out making your tube just a bit longer but made the same, then fish mouth a tube to the cage at the floor. or maybe fish mouth a piece of rectangle tube that lays flat on the floor and over to the cage and leave whats there in.


The bottom should be fine if its a hardend bolt. I like to use these mounts best.

http://www.jegs.com/p/AFCO/AFCO-Coil...12516/10002/-1

[BBR]

Can you cycle the suspension and check to see if the sheet metal is flexing?

x2 If no visible flexing occurs, I'd leave it alone, put some miles on it and keep my eyes peeled for signs of fatigue. It has the benefit of being supported by existing metal in multiple planes and your shock load is reasonably direct, so I bet it will be fine.

my 2 lincs

[CDMBill]

Yes, at both the shock mount and where the spring attaches to the frame.

Thanks for all the input guys. I'll look at the plating vs. the tie in to the roll cage back brace. My expectation is that the forces acting on the mount are primarily bi-directional along the axis of the shock which is why I wanted the barrek of the mount welded to the flank of the frame rail which is the thickest material on the car ~.095". The existing corner of the roll cage plate and the same thickness of material surrounds the barrel section axially.

Bob's point about high frequency movement has me thinking the plate is the best way to go with some rosettes to ensure that it can't pull away from the trunk floor frame rail section. I bounced the heck out of the car watching the top of the shock and mount and saw nothing in the way of movement.

Regarding the front spring eye, I added reinforcing plates years a go to stabilize the spring pocket. I also stitch welded the all the spt weled seems and overlaps and added some rosettes again to prevent tearing. This was stuff we always did on the NHRA stock eliminator Mustangs I had back in the day. I pull the bolts and clean and re-grease the plates for the Cal-tracs each season which gives me a chance to look for cracks. So far so good on a 41 year old car. We added additional plates on the top of the spring pocket insode the car when we did the cage in '05 using the same method.

Sharp eyed readers will see the potion of the upper rubber isolator that is coming out around the washer on the driver side mount. That isolator looked like that when it came out of the factory location as the factory hole is .825" vs. the Afco washer at .5". I've ordered some spares along with the tiny little cap screw that holds the sdjuster knob onto the shock. It fell in to the unibody somewhere when I was removing the shocks and as they are stainless i could retrieve it magnetically. Oh well.

On the lower mount I'd prefer a double shear mount but that wasn't in the cards for the location. I use these bolts which are hardened as the mount bolt. The previous mount also built by me was here same method, no issues after 5 years.

[SuperBuickGuy]

Here's where my concern is:


if you look at the weld to the frame, there is no penetration. Add to the issue is that metal isn't as strong there as where the hanger was originally located. My suggestion is to box up the sides of the frame rails (covering the old bushing), then weld that plate to the sides of the original frame rails. Weld those plates over the top of where it's currently welded to the frame. That would distribute the side load over the entire structure. At this point, cycle that joint enough and it'll break off. That wouldn't be an issue if the new bushing was captive within the frame, but it's not

[CDMBill]

While I thtink the welds were adequate I got to thinking about side loads as opposed to the compressive load the mount usually sees and added two plates from each of the mounting bolt flanges up to the frame rail and to the new cross member which hadn't been added in the picture above.

Thanks for the suggestion. I'm going to go ahead and add a plates to the shock mounts while everything is torn up and all the metal working stuff is out.

I've left the mount for the bushing accessable and useable as I built this with the idea that should I encounter a rules situation that requires completly stock suspension mounts I can go back to the shackles.

[SuperBuickGuy]

Do you have room to go up the rail 1" in a U shape? even 1/2" would do great things about keeping those side loads from ripping that flat plate off the bottom of the rails. Maybe another alternative would be to run a brace between the shackles, welded to the plates and tight against the rails.... just thinking out loud, I'll give you a full refund for all ideas you don't use