Replacing seat mounting bolts
Thread Starter
Burning Brakes
Joined: Nov 2008
Posts: 995
Likes: 1
From: Naples Campania
Replacing seat mounting bolts
I have swapped out seats before with buckets, adjustable, or just OEM replacements. My Corvette, however, needs new seat bolts. After previous owners pulled out the seats for unknown reasons and and scraped up the treads, they forced bolts on that do not belong there. They are stripped and pretty much useless. I can get the nuts and seats off, but I need to replace the bolts themselves. I haven't really looked under the car, so I am wondering if anyone has had to do this. How did you remove the bolts, what did you use to replace them, where are the bolts mounted, and how did you get the new hardware attached?
Thanks in advance for the help!
Thanks in advance for the help!
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The seat frame mounting studs (not bolts) go thru the floorpan and are permanently mounted to the floorpan.
To replace them will require removal of the stud, being careful to not damage the floorpan or making the hole larger. You can use bolts that are slightly longer and you will need to use some flat square steel plates to provide a mounting surface under the car. Something like a 3" square plate that is 1/8" or 3/16" thick. Drill a hole in the center of the plate and insert a bolt thru the hole and upwards thru the floorpan. Use some good RTV Sealant around the edges of the plate to keep water out.
Make sure the bolts are in the same location as the old studs so you won't have to re-drill or elongate the holes in the seat frame.
The replacement bolts should be at least a SAE Grade 5 (metric 8.8). Use a small flat washer on the top of the seat rail and a self-locking nut or nyloc nut. Lockwashers work too. The factory torque spec for the seat frame nuts is 20 ft-lbs.
To replace them will require removal of the stud, being careful to not damage the floorpan or making the hole larger. You can use bolts that are slightly longer and you will need to use some flat square steel plates to provide a mounting surface under the car. Something like a 3" square plate that is 1/8" or 3/16" thick. Drill a hole in the center of the plate and insert a bolt thru the hole and upwards thru the floorpan. Use some good RTV Sealant around the edges of the plate to keep water out.
Make sure the bolts are in the same location as the old studs so you won't have to re-drill or elongate the holes in the seat frame.
The replacement bolts should be at least a SAE Grade 5 (metric 8.8). Use a small flat washer on the top of the seat rail and a self-locking nut or nyloc nut. Lockwashers work too. The factory torque spec for the seat frame nuts is 20 ft-lbs.
Heel & Toe
Joined: Aug 2016
Posts: 18
Likes: 0
I know this thread is old - but just got a 1993 40th anniversary car today, and lo and behold, both seats have one broken stud (the outboard rear one). The stud is just plain broken off and gone. I can see the backing plate, under the car, with the head of the stud still attached. It looks like it is all welded to the floorpan.
So now what? Should I drill out the broken off stud, and just bolt through the bottom of the car?
Ugh.
Thanks
-Glenn
So now what? Should I drill out the broken off stud, and just bolt through the bottom of the car?
Ugh.
Thanks
-Glenn
Team Owner
Joined: Sep 2003
Posts: 25,412
Likes: 2,745
I know this thread is old - but just got a 1993 40th anniversary car today, and lo and behold, both seats have one broken stud (the outboard rear one). The stud is just plain broken off and gone. I can see the backing plate, under the car, with the head of the stud still attached. It looks like it is all welded to the floorpan.
So now what? Should I drill out the broken off stud, and just bolt through the bottom of the car?
Ugh.
Thanks
-Glenn
So now what? Should I drill out the broken off stud, and just bolt through the bottom of the car?
Ugh.
Thanks
-Glenn
The thread is a M8 X 1.25 so if you used a larger "spot weld remover" device I'd think you could remove the stud and use a through bolt with a "flange head" or drop one through and use a flange nut on the bottom. I've never needed to do it/never done it but I believe I understand whats needed.
A uni-bit Titanium-Nitride might do well also. Harbor Freight (never been there) should have both. 95343 for the spot weld bit, 91616 uni-bit. If you know an auto-body repair technician he/she will have both and they would be "quality" vs the lesser HF product.
I know a couple guys who have/use the Blair 11308 & 11310 seen in this link:
http://www.blairequipment.com/Spotwe...d_Cutters.html
Maybe someone will drop in whose "been there/done that" - I ain't!
Last edited by WVZR-1; Aug 14, 2016 at 02:59 AM.
