I've got some holes that the PO haphazardly drilled to install the rear sway bar on my del Sol. I'm wanting to fix this to install it correctly once I have my ASR brace on so I want to fill the holes and start over from the correct mounting points.

My question is when I go to fill the holes I'll need a "plug" to weld into the hole. I'd like to know the grade of steel I'll need to match the subframe's grade so the welding goes smoothly and retains the metallurgy of the chassis so weak points aren't created. Anybody know what grade of steel the chassis is?

***Please, I don't need other options (i.e. start over with a new car, ignore it, replace the subframe, etc.); I just need the grade of steel***

 

The welding rod/wire/filler and heat will change the tempering (make it brittle around the weld). And the steel will vary depending on where Honda got the steel for the frames (always from the lowest bidder). You probably want it plugged to keep it sealed right? (I dont know what re subframe is like). If that's the case any mild steel of the same thickness will work. Grab a correct size holesaw and cut out patches and weld em up. Avoid major heat if you really are worried about tempering of steel. Being round it won't have corners to crack out..

 

He drilled holes to mount a sway bar? Post pictures.

 

that^^

either you're off on the parts and locations or the PO was trying to kill himself.