Making and Installing the Firewall Battery Rack
Construction and Assembly
See this diagram for a picture of the following pieces. You'll need about ten 2" C-clamps to hold pieces together while you mark holes for drilling.
Cut two pieces of 1" galvanized pipe 2 3/4" long. File down the edges and verify accurate length. Place these two pieces of pipe over the original Civic mounting holes near the rear of the engine compartment on either side.
Cut four pieces of 1" wide by 3/16" thick steel bar 5 1/2" long. Drill a 15/64" (6mm) hole in one end of each bar 1/2" from the end. Install these four pieces on the Civic shock towers with grade 8 or better 6mm bolts and lock washers. Snug the bolts but do not fully tighten.
Cut two pieces of 1 1/2" angle iron, 1/8" thick. One piece should be 23 1/2" long (passenger side) and the other 15 1/4" long (driver side). Remove 1" of the vertical portion off the rear end of each of these pieces (see diagram). Drill a 21/64" (8mm) hole in the rear-most end of each piece 1/2" in from the end and 3/8" in from the outermost edge. Drill two 3/8" holes in the vertical portion of both of these angle-iron pieces, centered top-to-bottom and placed 5" from the rear-most end and 10" from the rear-most end.
For the shorter, driver-side piece, cut a 45 degree chamfer off the rear end of the vertical wall to prevent interference with the brake lines. For the longer, passenger-side piece, drill two 1/4" holes in the horizontal plane to attach the front electrical component board. One should be back 1/2" from the front edge and the other should be back 8".
Install the left and right pieces of angle iron that you cut in the prior step by threading a 8mm x 90mm long bolt through the rear-most hole, through the piece of galvanized pipe and into the original Civic mounting hole. Make snug, but do not tighten. Use small C-clamps to attach the angle iron to the front-most vertical bars bolted into the shock towers.
Measure the inside distance between the two pieces of angle iron, subtract 3/8" and call this length "Y" (typically near 31 1/8"). Cut four pieces of 1 1/2" (1/8" thick) angle iron to length "Y". Drill 5/16" holes in each end of the "Y" length pieces, 3/8" in from each end and 5/8" in from the vertical outside wall of the angle iron. Also drill 5/16" holes 17" and 27" in from one end as shown in the diagram.
Rest these four pieces with the ends sitting on the angle iron bolted to the shock towers as shown in the diagram. The rear-most piece will probably have interference with the brake lines just below the brake fluid reservoir, so you'll have to cut off a diagonal piece of the angle-iron to clear this interference. The front most piece will need to clear the motor adapter plate by 1/4", so you might need to adjust the clamp holding the left and right angle iron pieces to the shock tower vertical bars. This 1/4" distance will settle down to 1/8" as the batteries are put in the rack.
Align the four pieces so that there is 6 3/4" inside distance between piece 1 and 2 and 6 3/4" inside distance between piece 3 and 4. This is slightly larger than the width of the battery to allow for expansion and proper seating in the curvature of the angle iron. The 6 3/4" measurement was used for LifeLine batteries, so you might need to adjust this distance to support your own group-31 batteries. Make sure all four pieces are parallel with the rear-most piece aligned with the 1" cut-out in the left and right angle-iron supports. Use small C-clamps to hold all four "Y" length pieces in place.
Double check the clearance between the front angle-iron and the motor adapter plate. Double check that all bars are level and parallel with 6 3/4" spacing. Check that the vertical bars bolted to the shock towers are centered on the holes drilled in the vertical walls of the left and right angle-iron supports. When everything is good and clamped tight, use a fine-tipped permanent marker or scratching awl to mark holes on the vertical shock-tower bars and mark holes downward through the 5/16" holes onto the left and right angle-iron supports.
After the holes are marked, unclamp and disassemble all the pieces, drill the 3/8" holes in the vertical shock-tower bars and the 5/16" holes in the left and right angle-iron supports. Re-assemble everything. For the 3/8" holes, use 3/8"x16 by 1" long bolts with nylock nuts. For the 5/16" holes, use temporary 5/16 bolts with regular nuts to hold things together. These 5/16" bolts will be replaced by 5/16" all-thread to attach the hold-downs later.
Cut two pieces of 1 1/2" angle iron (1/8" thick) 22 1/2" long. Use small C-clamps to hold these two pieces under the rows of 5/16" holes drilled near the middle of the "Y" length angle iron. The rear end should be flush with the rear-most piece of angle iron and the front end should stick out the same distance as the passenger-side angle-iron support. If you draw a centered line on the horizontal face of the 22 1/2" long pieces, it will make lining up with the holes on the rack easier. Mark down through the 5/16" holes onto the 22 1/2" long pieces with a fine-tipped permanent marker. These two angle iron pieces will only be bolted to the rear horizonal support and the front one. Unclamp the pieces and drill the 5/16" holes in them. As in the passenger-side support angle iron, drill two 1/4" holes in the horizontal face of these two pieces. One hole should be 1/2" in from the front edge and the other should be 8" in.
If you have your batteries at this time, you might consider putting them in the rack, justified to the passenger side and close the hood to check clearance. Putting white masking tape on the top edges of the batteries and on the underside of the hood can help you see any interference with a flashlight as you close the hood. You may have to cut and crush a small portion of one of the hood reinforcements.
Assembly After Powder-Coating
After getting the firewall rack pieces back from powder-coating, some of the bolt holes might have to be re-drilled due to fill-in from the powder-coating process.
Place the two 2 3/4" galvanized steel tubes back over their holes in the rear of the engine compartment.
Bolt the four vertical bars to the shock towers with 6mm bolts, making sure that they are in the exact position as they were before powder-coating.
Place the left and right angle-iron pieces in place. Add the long bolts (with lock nuts) in the rear-most ends through the galvanized steel tubes into the original Civic mounting holes. Do not fully tighten yet.
Add four 3/8"-16 x 1" bolts with nylock nuts to attach the left and right angle iron pieces to the vertical vertical bars on the shock towers. Keep the bolt heads towards the center of the car with the threads pointing to the outside. Do not fully tighten yet.
Rest the four long pieces of angle iron in the left and right angle iron supports and line up the 5/16" holes. Make sure all four pieces are in the original location they came from before powder-coating.
Add four 5/16-18 x 1" bolts with nylock nuts to the four driver-side-most holes with the bolt heads up and threaded ends pointed down. Add two 5/16 x 1" bolts with nylock nuts to the two passenger-side-most holes in the center of the left angle-iron. Do not fully tighten yet.
Add four 5/16"-18 x 1" countersunk allen-head bolts to the holes 17" in from the passenger side, through the 22 1/2" piece of angle iron. Cap them off with a 5/16" nylock nut.
Cut four pieces of 5/16" all-thread (grade 8 or better) 9 3/4" long. Add a 5/16 nut to each piece, leaving 3/4" of threads exposed. Install these vertically down into the front-most and rear-most "Y" length pieces in the passenger-side-most holes and the holes 27" in from the passenger side through the 22 1/2" angle iron. Cap the bottom of each all-thread with a 5/16-18 nylock nut.
Tighten all bolts to secure the rack. This should now be ready for battery installation and hold-downs.
Licensed under the TAPR Open Hardware License (www.tapr.org/OHL)
Copyright 2008 Tim Kutscha