My project car came with a couple of seats that definitely aren't out of a Camaro. I'd like to keep them, as they're leather, fully electric, and quite comfortable (even have on/off side bolsters lol). Trouble is, the mounting holes are further apart than the rails in the frame, and lower too so if they sit on the rails I only have about 2" of space between my head and the t-top.

I figure I can solve both problems by removing the seat rails and making my own with some steel flat bar and bolts going through the floor from underneath. They would be welded on. My question is, how structural are the seat rails? I don't think the body would be prone to more flexing with them out as they run across rather than along the body, but want to be sure. Also, would putting the flat bar underneath prevent me from installing SFCs in the future?

 

Seat rails you can modify (I would make sure that they're damned strong, there are a lot of force on those things in an accident), but I wouldn't mess with the mounting locations- they are reinforced locations in the floor pan and moving them/using other locations is illegal both for street use and by most racing sanctioning bodies.

If you mess with them and something happens to someone sitting in that seat you can guarantee that if anyone catches it there will be all sorts of blame thrown your way even if it had nothing to do with the way the seat was mounted

 

I removed the rear factory seat support structure to get the driver seat about 3.5 inches lower. I now have a solid four inches of headroom with a Sparco Evo Plus seat -- sufficient for a headliner and helmet.

The factory seats support structure has decent cross section but is barely spot welded into the floor pan and is unwelded across the tunnel, and in my case suffered corrosion and cracking at the stud mounts, making the Sparco Evo's FIA cert pointless.

I recessed a 1"x2.25" .120 wall 1018 steel, gusseted structure into the floor pan, fully welded from end to end.
The seat bracket is 3/16 1018 and is held in place with 3/8-16 grade 8 fasteners with weld nuts inside the seat structure. The finished seat adapter also ties into the lap belt fastener locations.

I don't have photos yet of the completed mod but the attached photo gives the basic idea. The finished structure is overkill compared to the original.

It's not a trivial endeavor, but was necessary to get proper driver position with a fixed back seat.

 

@LT1swapper: That's kinda similar to what I was thinking, try to over-engineer the thing to the point where the rest of the car could fall apart and it'd still hold together. My rear support structure has enough rust that I could probably break the bolts out just by kicking the back of the seat, and as such, would actually be significantly safer if I were to modify or repair it. I'm kinda curious as to exactly how illegal "illegal" actually is - I mean, the car will have to pass a safety inspection before I can even register or insure it, so if there was a problem with the seat mounts wouldn't the shop that certified it get hit with the blame for passing it? Don't really want to do anything incredibly stupid, but I'm thinking if it's the same kind of illegal that, say, spinning your tires off the line is, I might just do it anyway.

I dunno, just kinda tossing thoughts out there, I've got a while yet to decide what I want to do - car needs a lot of other work before I start worrying about the interior. Thanks to both of you for the replies.

 

el_muerte,

Not sure what rules 83 Crossfire TA is up against, but I don't forsee any trouble running my car at High Performance Driving Events or driving on the street.
The majority of the seat installs I see on the internet are ergonomically a mess at best and unsafe at worst, so it may be that 83 Crossfire TA is referring to botched jobs. But if your seat structure is already a rusted mess, you need to fix it back to stock as a minimum.
As this seat install is for a GM High Tech Performance tech story, I have the luxury of consulting Sparco and Schroth who would let me know if I was on the wrong track.

 

Have not heard that before. I've seen more cars with 4x4 plates welded for different seat patterns than I can even count on all my fingers and toes.

-- Joe

 

Well, just because we've all seen horrendous hacks that somehow made it through tech on TnT night or rolling down the highway doesn't mean that they were OK, done right or legal...

 

Can you quote the rules or laws that you are referring to?

This is what I found for DOT regulations DOT Part 571.210: Standard No. 210; Seat belt assembly anchorages

 

I couldn't find anything either, and I've been in Law Enforcement for a number of years.

What he's saying though, is good advice - a lot of guys don't do good enough work to anchor a seat OR seat belts.

However, I still could not find anything indicating it was illegal to modify the seat mounting positions, however I found lots of information regarding moving or altering the seat mounting and anchoring for vehicles designated for handicapped persons.

-- Joe

 

Agreed. I have about 100 hours in the project right now, and I am still not done. Granted, it would go a lot faster if if I had to do it again.

The attached photo is the driver's side. The adapter bracket still doesn't have the sub strap crossmember on it and the adapter as a whole will get some additional gusseting, but this is pretty close to done.

 

Thanks for the input. I don't intend to modify the seat belt mounts at all, so I'm going ahead with it.

 

try this.. use GM (camaro) brakets get them to fit the aftermarket seats

Just finnished welding up the bracket leg (took out 1") to drop the pasngr seat down by 1 " bolts to floor studs just like GM wanted.

to use them with my aftermarket seats. and to get them low enof.
i had to use 2 pasngr side brackets. and no driver side brackets.
(they sit to High) looks factry. and works 100%

82-92 camaro seat brakets are cheap

 

I've got a power driver, and a manual passenger. What are they worth?

-- Joe

 

After running FEA on the load cases I decided to ditch the idea of combining the belt attach points to the seat adapter bracket -- just not enough room to properly gusset the lap belt tabs. The sub straps would work because the loads are much lower. I was designing to a 3200 lb static load per lap belt attach point.
Went back to the drawing board and welded up another adapter bracket without belt mount tabs and I am going to weld the belt attach points to plates in the floor.

Dropping an inch by modifying factory seat rails is pretty sweet. I am three inches lower and the extra two inches were a lot harder to come by.

 

thats what i took out of My Z28 (power seat)to save the factry seats
(still look brand new). and did not want to mod any parts off my car.

manl seat brackets $15 give or take a buck (power..dont know..dont use them)

photos shows rear plastic cap left off, to show factry Seat Mt
and GM slider rails

see..still like new.. taking them out to keep them that way.

this is the driver seat installed. factry black rail caps install ontop of the home made brackets.. got to keep that almost GM finnish look.