IRS Swap drilling required?

boston2k4 · Apr 11, 2012

im really set on putting the irs in my car.

and i read mixed reviews on the install?
some say its a bolt in affair others state you have to drill and mount plates?
are these plates on the frame / underside of the donor vehicle?
does anyone have a good link on the install in the 97 mustang pics would be awesome i just need to walk to the other side of base to load them :/
also i know the good and the bad and all that jazz. its just something i want ok im wierd i think it would be different!

i promise when i get home in june i will not ask for help like this by then my internet will not be all blocked and slow

twovalveterror · Apr 11, 2012

it is almost entirely bolt on. you have to drill 4 holes and then tap them. I'm not entirely sold on that solution though. cobras have a captured nut (or something similar) inside the frame to recieve the bolt. drilling and tapping an 1/8 inch thick sub frame is not even close to as strong in my eyes. I think I'm just going to weld my brackets on for a stronger mount.

make sure you get as much of the bolts from the IRS as you can. I've been waiting a week or two for the last couple fasteners I need to get here. the swap is pretty straightforward from there. I have heard of needing to bend brake lines, but I'll update you on that hopefully this weekend.

you can ask me anything about the swap, as I've said, I'm nearing the end of mine. there are a couple other guys on here that have done the swap as well. I'm sure they'd be of great help to you if they chime in.

Gallows · Apr 11, 2012

I never heard of tapping the sub frame. I thought you drilled into the trunk and added a piece of flat steel and used a bolt and nut.

twovalveterror · Apr 11, 2012

Gallows said:
I never heard of tapping the sub frame. I thought you drilled into the trunk and added a piece of flat steel and used a bolt and nut.

I seem to remember reading that somewhere. but I don't know what you'd do that for. I'll go out and take some pics to better describe how the upper sub frame mount works. if you could show me the link to where they did that, I'd like to see it.

twovalveterror · Apr 11, 2012

here is the upper sub frame bracket.

it uses the two existing bolt holes that were originally there for the quad shock mount, shown here.

here is where I have seen people drill and tap for the other two bolts that are on a cobra.

I don't know why someone would cut into the trunk floor, but I do remember seeing it before. I plan to weld along the front and rear edge of the bracket, rather than drill and tap holes. mainly because I don't think that minimal amount of thread would be good for anything but ignorant peace of mind.

on another note, I know I have to clean up some rust. it will be done when I drop the tank for welding.

hope these pictures help clear things up!

Gallows · Apr 11, 2012

I can't remember but I think it was on SVTP where that was done. My FTBR kit is supposed to be shipped Friday and I am hoping by the first of May to have it installed. I guess I'll see what the best method of mounting it is then.

Are you running new brake lines or modifying your existing lines?

twovalveterror · Apr 12, 2012

Gallows said:
Are you running new brake lines or modifying your existing lines?

I'll let you know in a couple days! I won't change anything unless I have to.

dutch · Apr 12, 2012

Drilling the holes is pretty easy if you have a powerful drill and a good bit, just use some strong bolts and a flat large piece of steel in the trunk. But I suggest having the brackets welded to the frame aswell, once everything is said and done and you're happy with the IRS, have a shop weld the little buggers for extra piece of mind.

boston2k4 · Apr 12, 2012

thanks for the info
twovalveterror i will go load the pics tonight at the rec center and see whats up i got a good irs lined up and dont want to pull the trigger unless it will work with ease

twovalveterror · Apr 12, 2012

dutch said:
Drilling the holes is pretty easy if you have a powerful drill and a good bit, just use some strong bolts and a flat large piece of steel in the trunk. But I suggest having the brackets welded to the frame aswell, once everything is said and done and you're happy with the IRS, have a shop weld the little buggers for extra piece of mind.

so you drilled through both sides of the frame rail and into the trunk? I like that better than tapping a hole in the rail. how long of a bit did you need to get through all that?