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Hybrid Hatchback
66 Posts
Discussion Starter #1 (Edited)
I wrote this a couple years ago, but hope it helps someone....

Disclaimer: This write-up is intended for informational purposes only, to be used in conjunction with the appropriate knowledge, skills, service manuals, documents, equiptment, tools, and common sense necessary to complete this swap. This write-up does not claim this to be the "correct" or "only" way to perform this swap, merely the method and manner the author deemed safest of the available options at the time. Your conditions and circumstances may vary, this information is based on a 1991 US model Si. Jaime 91SiB18 will not be held responsable for unqualified chumps tearing up their rides.


I started this project because I have the JDM Power Windows and Door Panels waiting to go in. The JDM Power Window Door Panels don't allow for door mounted seatbelts.

-Parts/Materials/Tools Required
1) 88-89 USDM or JDM Pillar style seatbelts/complete with mount bolts, in good working order.
2) (2) Factory 10mm short mount bolts
3) (4) Grade-8 "7/16-20" nuts
4) 1/8"x3"-3ft flatstock weldable mild steel
5) a section of posterboard/cardboard for templates
6) a fine tip permanent marker
7) a sharpie
8) a straight edge
9) an angle grinder with flapsand disks, cut-off disks, grinding wheels, and a wirewheel.
10) a 20amp circuit(minimum) close by
11) a good wire feed MiG welder on gas -at least CO2, but best results with 75/25(Argon/CO2)
12) a high speed drill with 1/2" bit
13) a center punch
14) right angle welding magnets
15) leathers or non-flammable drop cloths to protect interior
16) a 10mm, 12mm, and 17mm socket and wrench
17) a big "step-bit" drill bit --or-- rotory die grinder
18) tape
19) primer

-Helpfull Items, but not required
1) Plasma cutter
2) Iron Worker, for cutting and punching holes
3) Bench mounted grinder and wire wheel

-The Problem:
The weld nuts are not behind the hole on the pillar

...and the opening of the can for the spool is shaped a little different than the 88-89's can.

As you can see there is no material to attach the lower 17mm load bearing bolt to.

The seatbelts require (3) load bearing mount points and (1) 10mm hanger/stabilizer mounts/per side. The weird part is that, as far as I can tell, these seatbelt mount bolt/nuts are the only SAE threaded things on the entire car. They are "7/16-20" I don't know why, they just are.
The final attachment point/weldnut at the end of the belt, next to the seats/doorside, IS there, as well as the 10mmx1.25mm standard honda metric threaded hanger/stabilizer weldnuts at the top of the spool can. So you are left to find a way to attach at the two points on the pillar.
My solution was to make some plates with the 7/16"-20 grade 8 nuts welded to a 1/2" hole punched with an Iron Worker. The Idea is to open the hole in the pillar enough for the nut and weld to pass through and surface then weld the plate to the face of the pillar. As for the spool cans, I made the same type of plates except for these will fit into the can opening behind the factory sheetmetal and welded from the front.

-First, strip the seats out for room to work and to protect them from harm. Then, strip all the rear interior plastics to gain access to the work areas. Next, you will need good accurate templates of the plates you intend to make.
<I'll find and post pics of my templates>
-once the templates have been fit checked you'll need to "locate" the correct 1/2" hole placement. The pillars easy, it's the lower can hole placement that is critical. I hung the spool from the 10mm bolt and used a straight edge horizontally to mark the sides of the can and established a vertical centerline and marked it. Next you remove the spool, and place the template in and secure it with tape as you intend it to fit. Use your straight edge to connect your two horizontal marks and draw a line on the template with a sharpie. Also use your straight edge to connect your 10mm hanger bolt and your vertical centerline mark. Draw your line here to intersect the previous line, this gives you accurate hole placement.
-Fab your plates

The materials I used...

Continued below...
Hybrid Hatchback
66 Posts
Discussion Starter #2 (Edited)
The materials I used...

Plates before holes punched and nuts welded


-Protct interior as necessary
-Use a rotory die grinder or short fat step bit to evenly open the pillar hole up to accept the nut and weld(@1"+) so the plate fits flush
-use a flap sanding disk on the angle grinder to prepare the surfaces for welding
-Use a welding magnet or clamp to hold the pillar plate in place.
-Weld. Seam weld all the way around for strength, you have to trust your life on it! :idea:
**as for the lower can plates, pay special attention not to damage the brake and fuel lines that are near**
-Make sure to remove the seam sealer near the weld site with the wire wheel
-It is important to draw the lines from the templates onto the lower can plates. This allows you to line up the hole to the correct location.
-Tack weld the lower plates and test fit the spool.
-Make corrections-or-finish weld the plate
-Primer to prevent rust

Driver pillar

Passenger can

continued below...

88 Civic Hatch
925 Posts
cool stuff rep for you!

formerly allnaturalrex
1989 honda crx si
4,639 Posts
that something ill be planning soon as well thanks
Hybrid Hatchback
66 Posts
Discussion Starter #8
I was told on another fourm, I had the thread size/pitch wrong and it actually was metric. Can't remember offhand. I'll look up what the guy said.
From what the guy said, the two sizes are virtually identical. It's just a weird metric thread pitch, I guess.
The SAE bolts I used were the only ones I could find that fit. They fit perfect with no issues.
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