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When I build mine I will move the battery to the engine compartment. At the build school in February another student connected the cables to the wrong terminals, he could not see the top of the battery under the body. Fried the fuel injection. We did not have a car that could drive at the end of the class.
I have the FFMetal box that was mounted in the center of the trunk with a 4 link. Just moved the battery box today so I could mount the 3 link frame in position. This was all done with the car complete and I was able to get my #34 battery in. I still need to do an aluminum patch but it is all covered with carpet so it will not be seen. I like the trunk mount for several reason; it’s in the trunk, it’s hidden and it’s not under my hood. Did I mention, I don’t want my battery under the hood?
FA57F2B8-EB04-4647-8F24-561F74F98769.jpg
MK IV Base Kit #9370 w/ FFR Lower Control Arms, donor 1996 Cobra 4.6 L DOHC; stage 2 Comp Cams, Manley forged Pistons & Rods, IMRC Delete Plates, T-45 transmission HD extra build w/ single disconnect reverse mod, 3-link w/ Koni Coil Overs 3:73 rear end. Painted and re-assembled Jan 2022.
WIS89 liked this post
Has anyone done a battery box behind the rear wheel on the driver's side of an MK4? There is a a lot of real estate there for a battery, extra storage, etc. As I am contemplating my build, I am envious of this space and making it useful.
#10333 Complete Kit, Carbed 427w, TKX, IRS and many other upgrades
- Order Date: September 11, 2021 - 20th Anniversary of 9/11
- Delivery Day: April 1, 2022 - April Fool's Day
- First Start and Go-Kart: January 20th, 2023
- Graduation Date: July 4th, 2023 - Independence Day!!
- Legal Registration Date: October 4, 2023 - My Birthday!!
Visit my MKIV Build Thread (#10333)
There is a guy out in So Cal who does it. His first name is Frank I believe and if you go on to YouTube he is i.e. 427 Garage. I know he has done it on a MKIII, I assume he also does a MKIV.
MK IV Base Kit #9370 w/ FFR Lower Control Arms, donor 1996 Cobra 4.6 L DOHC; stage 2 Comp Cams, Manley forged Pistons & Rods, IMRC Delete Plates, T-45 transmission HD extra build w/ single disconnect reverse mod, 3-link w/ Koni Coil Overs 3:73 rear end. Painted and re-assembled Jan 2022.
Here is how I did my dropped trunk. Made the panels myself. It is a VERY worthwhile change.
Trunk 1.jpg
Trunk2.jpg
FFR MkII, 408W, Tremec TKO 500, 2015 IRS, DA QA1s, Forte front bar, APE hardtop.
https://youtu.be/rr_Z2N0ErQk?t=152
This video will start at the right point. Even if not doing the battery box there, it's very useful to add it as an extra storage for small items.
Complete novice who doesn't know what he's doing.
MKIV with BPE 347 & TKX. IRS. A crap ton of mods.
Build thread
Just to offer a point that I haven't seen discussed.
Battery weight and placement might matter to you. Many talk about corner balance and adjusting coilovers to adjust the balance. A good plan from what I've seen. Moving a 40# battery around will change things, good or bad that's up to you and your scales to determine. Perhaps not real important on a street car but more important on a track car.
In a past life and different car the battery was on the driver's side behind the rear wheel. Corner balance wasn't great, way heavy to the left rear. We pulled the battery and placed it over the passenger side headers about 10" in from the outer body. Most of the corner balance issues were resolved or got significantly better. For those cars the left rear was the heavy point, the front right the light. All this was checked on properly used scales.
Another thought about lightweight batteries is securing Mass. It's a whole lot easier to tie down a smaller / lighter item than a larger / heavier piece. I've seen what a 40# battery does in an instantaneous stop.
BTW, I'm regrouping and looking at the ATX20-HD as an option as Hooper has mentioned. Just over 5# and $399 MSRP. Opens up options for placement while reducing concerns for balance.
https://antigravitybatteries.com/pro...-oem/atx20-hd/
Jim
2016 Mk4 Challenge Car, IRS, 3.31 Torsen, RDI Aluminum 427w, AFR 225s, Vic Jr. ProSystems 780 HP, TKO-600 w/Liberty mods. Forward cage. Levy 6/4 piston Wilwoods. Not completed yet, will be a streetable track car.
2004 Superformance MkIII #1855, 2007 Superformance MkIII #2584 purchased in 2012 both sold.
Another happy customer using the FF metal drop battery mod. It is tucked away and opens up the trunk.
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FFR MK4 Roadster (9945) complete kit, delivered 12/4/2020, First start and go kart 5/7/2021. Legal 8/14/2021, Paint finished 7/18/2022 (Viking Blue). 347BPE CI, TKO600, Moser 8.8 3link 3.55, Halibrand 17x9 17x10.5, power steering. Carbon Fiber Dash. Carbon Fiber trans tunnel, adjustable Kirkey Lowback Vintage seats, Vintage gauges, RT drop trunk mod, FFmetal drop battery mod and trans tunnel, Forte front sway bar. Forte mechanical throttle linkage, RT gas pedal. www.covespringsfarm.com
MK4 Complete Kit #10315 / Coyote G3 / TKX / 427 HardTopBuild Thread Production Date: 2/26/22, Registered 5/19/22, Graduated 3/1/2023
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Complete novice who doesn't know what he's doing.
MKIV with BPE 347 & TKX. IRS. A crap ton of mods.
Build thread
I don’t think anyone said they put a permanent panel over a battery box or at least I didn’t read it that way. Mine has a cover over it with screws to have access to the battery.
MK IV Base Kit #9370 w/ FFR Lower Control Arms, donor 1996 Cobra 4.6 L DOHC; stage 2 Comp Cams, Manley forged Pistons & Rods, IMRC Delete Plates, T-45 transmission HD extra build w/ single disconnect reverse mod, 3-link w/ Koni Coil Overs 3:73 rear end. Painted and re-assembled Jan 2022.
I was just responding to someone's comment:
"At the build school in February another student connected the cables to the wrong terminals, he could not see the top of the battery under the body."
No harm, no foul, just responding to what I had read, perhaps it was different than how I read it :-)
FFR Roadster Delivered 9/16/21
Forte 427 Fuel Injected with TKX Transmission
Forte's Axle
CaptB liked this post
MK4 Complete Kit #10315 / Coyote G3 / TKX / 427 HardTopBuild Thread Production Date: 2/26/22, Registered 5/19/22, Graduated 3/1/2023
zee liked this post
All,
Thanks for the great responses to this post. I decided to fabricate my own drop box in the rear similar to some of what was shown here.
CaptB liked this post
I have the Breeze battery mount (https://www.breezeautomotive.com/sho...-1-4-roadster/). It's a well-made part and I highly recommend it.
I fabbed a spare tire mount for my trunk (for a donut spare), so putting the battery below the trunk floor was no bueno for me.
David
My Saving Grace: John 3:16
FFR6687, Graduate #39 in the Class of 2009
The Factory Five Forum March 2012 POM
Mrk III, 331 stroker, Borla stack injection, T5, 3:55 IRS, Power steering and brakes. Kleiner body & paint
nucjd19 liked this post
For those of you using the Breeze kit, the site says it’s made to fit MK 3 and newer. Anyone see any issues with it fitting a MK II?
My Coupe Build Thread: https://thefactoryfiveforum.com/show...65-Coupe-Build
My Roadster Build Thread: http://thefactoryfiveforum.com/showt...ter-Build-9754
Member of the The Gateway Cobra Club
Dave's Cobra YouTube Channel: https://www.youtube.com/channel/UCbk...npK1UZHj4R-bYQ
No offence to Greg, but we've got him beat on the rear, fender mount battery by about 10 years. I'll see if I can dig up the original thread posted on the forum but here's a link to answer one of the questions about it on our fb page dated April of 2016. By far my favorite spot to mount a battery.
https://www.facebook.com/IE427-89165...90926444277008
Found it. August 2010
https://www.ffcars.com/threads/new-b.../#post-2303541
Last edited by i.e.427; 07-30-2022 at 10:52 PM.
I put mine up front. It’s clean, easy and very accessible.
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Last edited by Blitzboy54; 07-31-2022 at 06:36 PM.
Build 1 MK4 #10008 - Delivered 03/03/21, Graduated 7/20/22 - Sold 6/6/24 Build Thread #1 https://shorturl.at/K9fuy
Build 2 MK4 #11061- Delivered 08/24/24 Build Thread #2 https://shorturl.at/OZowi
Build 3 35 Pickup #329 - Delivered 10/28/25 Build Thread #3 https://shorturl.at/Ty4QQ
If using the FFmetal trunk mount kit with solid rear axle:
I have the 289 kit with solid rear axle. I used the FFmetal kit and it initially interfered with the travel of the rear differential. FFmetal is an awesome, well built unit, but I had to modify it by raising it up 2 inches to clear the diff travel.
build thread: http://thefactoryfiveforum.com/showt...-USRRC-vspeeds
Build School: July 14-16, 2017
Kit purchased: July 25, 2017
Kit delivered: September 13, 2017
First Start: December 22, 2018
Body painted and kit completed and drivable: July 2019 (but still not done)
CA SB100 Registration: January 2020
Mk4 - 289 USRRC Roadster kit, Roush 427SR with Schneider Racing custom camshaft, Fitech EFI, TKO600 (.64-5th gear), 15" wheels, stock brake calipers, under car exhaust with Spintech 7000 muffler, no roll bar, Russ Thompson turn signal, removable steering wheel, and many other small upgrades and modifications
FYI, that's what the big hole in the bottom of the box is for. Just put a 4x4 under the battery and use your floor jack to lift it up. Or enlist a friend to get underneath the back of the car and push up. In 17 years, I've removed my battery 3 times by myself and it just lifts right up and out - it's not easy, but totally worth it. The weight in the back in good, the space it frees up is great, I have remote battery terminals in the trunk so I can charge the battery. There's really no negative to having it back there.
Tip: Leave the handle on the battery and use it to lift the battery out in 5-7 years.
Last edited by Bill_VA; 08-01-2022 at 08:46 PM.
Non-donor - Engine Factory 351w/400hp - TKO500 - 3-Link - Cobra brakes - FFmetal - Wilwood pedals - FR500 wheels - NCPainter
Owner of FFmetal.com
Railroad liked this post
X2 on Bills experience. To the naysayers It is an urban myth that the battery is difficult to remove. It really is time to move on.
Mk.4 FFR supplied Right hand drive
Received 12/2012 completed 12/2019
Gen1 Coyote / TKO600 / IRS
Lots of mods to make compliant for Australian design rules
On the FFMetals box. Anyone happen to have a couple pictures of the clearances we are left with on the 3-link cross bar and diff cover when using this box?
There's not a ton of clearance, but just enough. I even had an aluminum rear diff cover. Never had an issue in 18 years.
BTW, I own ffmetal.com. Ask me anything.
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Last edited by Bill_VA; 02-11-2025 at 01:26 PM.
Non-donor - Engine Factory 351w/400hp - TKO500 - 3-Link - Cobra brakes - FFmetal - Wilwood pedals - FR500 wheels - NCPainter
Owner of FFmetal.com
battery box (1).jpg
Unconventional.
Nice
I ordered it todayI guess given how tight it is I didn’t think to ask if it will fit with the Ford GT500 finned cover?
My setup is same as yours with the exception of the diff cover.
Hopefully my finned cover does sit back any further than yours
IMG_1789.jpg
Last edited by Doc76; 02-12-2025 at 01:33 AM.
My build thread https://thefactoryfiveforum.com/show...Roadster-Build
Thread on Stainless Steel AN brake lines.
Thread on fasteners and torque wrenches.
Thread on Wilwood & Tilton master cylinders
My argument for a rear battery.
1. These cars need all the weight in the rear that you can get.
2. Batteries don't like heat.
3. Engine compartment looks better without it.
4. You will likely not need to touch the battery for 7 - 10 years, so it doesn't need to be very serviceable.
5. If you do need to remove it, the FFmetals box has a hole in the bottom. Use a piece of wood and a jack and it pushes it up for easy removal.
FF Metals box will not fit if you’re running a GT500 finned cover on a Ford 8.8 solid axle 3-link. It hits.
I will add this is a super nice piece however and Id like to find a smaller battery that may allow me to notch the box and still use it. Very well made, worth the mod and changing a battery if there’s a sufficiently smaller one.
Any suggestions on battery options would be appreciated.