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Vorshlag 2015 Mustang GT Road Race Build #TRIGGER

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  • #16
    continued from above

    The radiator hoses we make have proven to be reliable over the years. We're just trying to connect the radiator to the engine with hoses that have some flexibility, the right sizes, and never leak. The hoses often need to compensate for size changes between the water pump and the radiator; 1-1/2", 1-5/8" and 1-3/4" are all common sizes.

    We start at the ends, sourcing these from Pegasus, HPS, and others. Parts took weeks to all arrive, test fit (above left), then it was time to connect the ends with aluminum tubing - all while trying to leave as much access room and radiator exhaust airflow room as possible. Sure, we could have modified the radiator and water pump to use -20 AN ends and built AN braided hoses for all of this, but it adds 5x the fab time and cost - plus makes sourcing a replacement water pump at a remote race weekend impossible.

    We tend to make the hose bends and the adaptation between diameters on these silicone hose end sections. We connect the hose ends & bends on this install with straight 1.5" OD aluminum tubing, as shown above. We add these raised beads on the tubing at the ends, to help secure the hoses, using our little bead roller. Sure, you can often hack together some OEM rubber hoses from a car parts store, but these silicone + aluminum assemblies look good, work well, and do not leak - when built correctly.

    These also have just enough flexibility to allow the engine a little movement (from torque). We use these turbo style T-bolt clamps to secure each junction, which have smooth inner clamp surface - unlike worm gear hose clamps. I will talk about the "steam vent" port and plumbing we added in the highest hose (see above right) in a future post.


    The trunk of this car has two GIANT mufflers, a differential cooler, battery, remote surge tank and more. The rear seat is never going back into this car, so we have a giant hole between the trunk and the cabin. So let's make that hole even bigger!

    To make the trunk firewall the rear speaker deck became pointless - it had two massive holes in it, plus lots of little holes and raised bits. Brad and I discussed this in February and he marked the main upper "structural beam" at the upper leading edge. This ties the two shock towers together and we want to keep that structure for now. The perimeter was marked and he used lots of tools to cut out this piece.

    This speaker deck amounted to only 2.5 pounds (above left), but there were some raised sections in the remaining portion (above right) that had to be cut & ground away so a flat sheet could go over this panel with tight gaps. The point here is to seal air, fumes, and potential fuel / fire from reaching the cabin, so tight gaps to the remaining structures the firewall bolts to are key.

    Brad got all of the metal trimmed and flat, taped off the raw ends and primed them - no more rusty metal - then got to work on the two pieces that would be made from aluminum sheet for the firewall.

    Hot bits in the trunk with big openings that need to be sealed off from the cabin, as seen above.

    The main "vertical" matches the back seat angle and mounts to a flat section of vertical structure on both sides of the main opening. This sheet was relatively easy to shear and fit to the car. The upper deck replacement was trickier and Brad made a full sized cardboard template for that.

    There are two other portions that will remain in place on the sides of the back seat opening (see above left). These are riveted in place. The main vertical panel is bolted in place with button head bolts into rivnuts. The upper panel has a bend along the top leading edge and that bolts to the cross structure and overlaps the vertical panel (see above right). There are bolts along the back edge of the upper panel as well. Don't worry, the Lexan rear window will be removed with bolts as well - so if we need to remove this firewall we can, just takes a bit of time.


    Things were really speeding up on the project here - with a bulk of the work in this post done in February '22, when we had a gap in customer work while we waited on a bunch of parts. Instead of making the trunk mounting complicated I decided to go ahead and ask Brad to install the stock trunk release latch and striker. It has never been closed up until now...

    As I mentioned in previous posts before, this is an Anderson Composites carbon trunk, and it is very light - but has all the features and mounting points of the OEM trunk. This allows all of the factory hinges, brackets, and latches to bolt right up. As you can see above it also fits very well - we just bolted it on, and it fit like this.

    Then it was time to really look at the trunk release. There won't be "keys" or remote solenoids on the doors or trunks on this race car, so we kept it simple and used an extra Lifeline remote fire bottle pull handle cable as the trunk release (above right). This would attach to the "emergency release" handle on the latch, mandated to be inside all trunks - in case someone is trapped inside. Brad made a bracket to mount the cable pull to the inner sheet metal behind the passenger door and the handle is reachable from the passenger side window opening.

    Simple, effective, easy to see - and we'll add a proper label to the "pull" and a decal outside that window pointing to "trunk release", too. First time we have closed the trunk on this car, which was a nice thing to check off the ever shrinking To Do List.


    As I have stated before, we're re-using an OEM fuel tank in this build along with a remote surge tank. This mega-stripped salvage car came with nothing back here - no tank, zero fuel system plumbing, nothing. So we had to track down some OEM bits (tank + stock pump / float assembly + in-tank crossover hoses) and then build the rest.

    We got a stock fuel pump and sump assembly from my buddy Paul at Tri State Autoparts, and then got to work modifying that. The stock pump will be used just as a lift pump, which should be more than adequate at pushing fuel from the stock tank to the Radium remote surge tank.

    Paul left us the stock "pig tail" so we can wire up the stock pump easily. We've drilled into the top of this plastic housing for the "overflow" return from the surge tank at the top. Then the quick connect for the stock feed line from the stock pump has an adapter to a -8 AN end, as shown above right. That's how we get fuel out of the stock pump and excess goes back in.

    The feed and "overflow" lines are both -8 AN braided Fragola hoses, which Doug built and attached to this side. These feed up through the back seat and unto the trunk. The top of this side of the fuel tank will get another cover to act as a "firewall" to the cabin - I'll show that next time.

    The stock filler neck nipple (not shown) connects to the filler neck hose, which is the only stock plumbing hose left on the fuel system. Above left is the big 5/8" quick connect for the "vent" on the stock tank. This allows air to escape when the tank is being filled as well as to allow air back in when the fuel level goes down. We found this AN adapter from Motion Raceworks and it connects to a big -10 AN hose that goes to the vent stack, shown below.

    Next up comes the fuel tank vent system, and all this was done so we can do away with the factory charcoal filter (which is long gone). We are trying to vent the tank for filling and use, as well as make a "rollover valve". We started with a valve cover breather with a 5/8" opening, then a 5/8" barbed fitting to -10 AN, and finally this Vibrant -10 AN/ORB one-way check valve. The check valve was opened up and the spring modified to have a lower spring pressure. This way if the car ever rolls over on its lid, it acts as the rollover valve. It still should have enough spring pressure to keep the fuel separated from atmosphere as a check valve. If there are excess fuel fumes in use we will address this then, but with the sealed trunk firewall, it may be a non-issue.

    Doug made a bracket to hold for the lower check valve portion, then machined that fitting to work like a bulkhead fitting at the bracket. The check valve is mounted at the trunk floor level (as shown below), then a ~18" long hose goes up to another bracket at the top of the trunk, which mounts the breather. This is mounted higher than the external fuel filler neck on the fender, to keep fuel from ever coming up and out this vent.

    Next up was the Radium Remote Surge Tank, which we spec'd out with two Walbro 450 LPH pumps. This is tad overkill for the Phase 1 engine, but the single pump setup was a bit short. This has room for up to 3 pumps, and we will add a third when we go to Phase 2. We ordered this one "bare" so we needed to add the pumps, fuel hose, and wiring.

    These setups are modular and easy to work with. We ordered it made for the Walbro 450s and Doug made quick work of the assembly. The included screen at the bottom is made to hold these Walbros and he used submersible hose for the connections at the top. The included wiring was connected to the machined Radium top plate, which has wiring bulkhead connectors for all 3 pumps (6 posts) and another spot for a fuel level sensor.

    We added this optional fuel level float sensor, which basically tells you that the surge tank is NOT full - which is usually a "OMFG GET TO THE PITS NOW" warning. We'll mount a big LED in the center stack to warn the driver when this ever happens.

    The Radium sensor has the two pink wires that come out of the hole, which is sealed by the float assembly from the underside. As you can see the float only moves about 1/2" and it is near the top of the surge tank, letting you know you have drained the main fuel tank and are on the emergency reserve that is within the surge tank only.

    With the pumps and sensor installed and wired inside the Radium surge tank it was re-mounted in the trunk and the fuel lines plumed to and from that to the main tank. Two of these line run under the back seat floor and into the trunk, as shown in the two pictures above. The other two lines go to the rear bulkhead under the car for the main -10 / -8 lines to and from the engine bay. Fuel system plumbing is now complete - wiring and relays will happen in the next installment.


    I have a lot of experience with car batteries, which can be made very light - but it always comes at a cost. After 3 decades of this stuff I have settled on larger batteries of AGM / gel cell types. Of the Optima series I like their 75/25 group options, and on a race car we use the heavier Yellow Tops (thicker plates/can be discharged to zero) vs the lighter Red Tops (thinner plates/higher CCA).

    Nobody makes a good battery mount for these, but we do - shown below. Our mount is a steel lower tray we CNC cut and bend, then an aluminum upper. We've used these in numerous race car builds. First step is to find a good place to mount it.

    I looked all over the LS550 for a spot and had my eye on this this lateral cross beam in the forward section of the trunk floor. There was a thick layer of sound deadening material here but otherwise it was flat, so I asked Doug to use a heat gun and scrape that area clean.

    The bottom of our battery tray has 6 holes pre-cut for hold-down bolts, which can sit above the top of the tray and fit inside the voids on the bottom of these spiral wound Optima designs (see above left). I asked Doug to add 4 more tabs for even more bolt holes - because the section where we can bolt down the steel tray is "blind". This area is a thick hollow section and we would need to add Rivnuts here to mount the battery.

    Yes I know this is less than ideal, but it was the "least bad" spot to put the battery for easy access, weight bias, and where much of the rear wiring would be anyway. These are LARGE for rivnuts, they were installed with a pneumatic gun, and there are eight of them. This battery is not coming loose in any crash, and we have a bomb-proof rear bulkhead right in front of it. I have zero worries here. I will show the battery wiring in the next forum update.


    Some of you saw in my last post where I talked about buying this narrow body 2006 C6 we bought last year. We bought this to hold me and my wife over until this LS550 and her LS 86 are both on track, to keep our track skills fresh and to not wither away behind a keyboard for the ~3 years it took us to get this LS550 almost ready. Some wondered if this C6 would be a distraction or replacement that kept us from working on our two race cars.

    We had upgraded to these cheap flow formed 19x10" wheels (2 sets) and 275/35R19 Hankook RS-4s - which I bought for long term testing consistency, but as an "endurance" 200TW tire is gives up some speed. We chased a particularly nasty ABS issue on this car for a long time, but eventually just punted and swapped in BMW Mk60 ABS and that solved that. This ABS fix & 275mm tire upgrade helped this stock LS2 powered (360 whp) car go from 1:30.0 to 1:26.2 lap times at MSR on the 1.7. Then this 3100 pound C6 got MCS RR2s coilovers and it dropped nearly 4 more seconds into the 1:22 range on these same tires just a week ago.

    Honestly, this big lap time drop on the C6 motivated me to get our LS550 finished - because this C6 is roughly the final weight we will be at in this S550 (see recent weight check, above left), but we should start phase 1 at nearly +180 whp and be on better 305mm RE-71Rs (I have a fresh set to test with) and then the 315mm Hoosiers.


    I think this is a good place to stop, before this post gets too long. This round of updates caught us up with work done into March 2022, which is close to when I'm writing this. We have some more work completed during the period while I was writing this - the heater core is mounted, the coolant reservoir as well, and the Peterson vented oil catch can. Some small plumbing to wrap up on this round, too.

    The carbon doors are already being fitted to be installed soon, to keep the total weight down for Phase 1. Just some final wiring to knock out, digital dash, and tuning. Then we'll be on track "sooner rather than later".

    Thanks for reading!
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev