Got IRS??

jrichker · Jan 17, 2007

Isn't the IRS from the 93 and later Lincoln Mark VIII the same basic unit as the Cobra IRS? There are probably a lot more Mark VIII's in the junkyards than 99+ Cobras.

1990Coupe · Jan 17, 2007

jrichker said:
Isn't the IRS from the 93 and later Lincoln Mark VIII the same basic unit as the Cobra IRS? There are probably a lot more Mark VIII's in the junkyards than 99+ Cobras.

i would think tho that the cobra ones have more beefy rear's and maybe stronger axles??

seijirou · Jan 17, 2007

jrichker said:
Isn't the IRS from the 93 and later Lincoln Mark VIII the same basic unit as the Cobra IRS? There are probably a lot more Mark VIII's in the junkyards than 99+ Cobras.

Beats me, I'll have to see if I can find one and take a look. This is the first I've heard of it.

simplyJ · Jan 17, 2007

I went into the floorpan area for the vertical bolts. I simply used large washers to spread out the compression force. I am still debating whether or not to weld in 12 gauge support panels in the rear. It just seemed overkill at the time given the other two horizontal bolts through the framerail

soylentgreen · Jan 17, 2007

jrichker said:
Isn't the IRS from the 93 and later Lincoln Mark VIII the same basic unit as the Cobra IRS? There are probably a lot more Mark VIII's in the junkyards than 99+ Cobras.

I don't believe so. I seem to recall the Cobra IRS was a completely designed from the ground up.

bstrd86 · Jan 17, 2007

1990Coupe said:
im lovin the car! and the rims? if you dont mind me asking how much did the IRS set you back?

I paid $450 for my IRS, I see them going usually for more than that. As for the vertical bolts, I cut holes in the floor to gain access to the inside of the frame rail and ran short bolts. Carpet covers them up just fine. The Lincoln rear is the same as Cougars / T-birds, not like Cobras.

25thmustang · Jan 17, 2007

bstrd86 your car is easily top 3 favorite fox Mustangs. The wheels, stance, IRS, exhaust. everything just looks insane. Get her running and paint it up and it will probably be the best looking Mustang I have seen! Very classy!

seijirou · Jan 17, 2007

simplyJ said:
I went into the floorpan area for the vertical bolts. I simply used large washers to spread out the compression force. I am still debating whether or not to weld in 12 gauge support panels in the rear. It just seemed overkill at the time given the other two horizontal bolts through the framerail

Only one of my horizontal bolts lined up. The other one I would either have had to drill new, or cut the bracket to clear. But cutting the bracket didn't look like it was going to leave much metal left for it to do anything. I never did drill the hole for that bolt. On my first install I also went into the floorpan. I welded in some square plates to reinforce that floor area. I wasn't sure what the loads would be so I did it as a security measure.

I think maybe this time I'm going to cut a window into that framerail and install nuts so I can use shallow bolts. One thing I will miss though, that long bolt into the rear floorpan sure was a great ground location

seijirou · Jan 17, 2007

I got mine complete with brakes and cables for $500

bstrd86 · Jan 17, 2007

25thmustang said:
bstrd86 your car is easily top 3 favorite fox Mustangs. The wheels, stance, IRS, exhaust. everything just looks insane. Get her running and paint it up and it will probably be the best looking Mustang I have seen! Very classy!

Thanks! I'm kind of on a budget yet I'm stubborn and want it to look a certain way, so things are kind of slow sometimes.

795.0pacecar · Jan 17, 2007

seijirou said:
On the contrary. If you're coming off a stock 4 link, you notice a massive increase in handling. Especially considering most of the stock rears are beat into the ground and sloppy as hell.

My dad swapped an IRS on his mach 1, the handling improved very little, it just rides a lot nicer. This IRS he has also has urethain bushings, the stock rubber bushings are pretty sloppy themselves. Let me remind you 99-04 cobras are not very good handling cars, compared to a GT they are.

seijirou · Jan 18, 2007

795.0pacecar said:
My dad swapped an IRS on his mach 1, the handling improved very little, it just rides a lot nicer. This IRS he has also has urethain bushings, the stock rubber bushings are pretty sloppy themselves. Let me remind you 99-04 cobras are not very good handling cars, compared to a GT they are.

They're also heavy pigs compared to a fox.

What motor is in your dad's mach 1? And what has he done to the front suspension? Nose weight plays a role, aswell as overall weight. And if your front suspension is lightyears behind the rear suspension, well there's only so good it's going to get.

I started out with a modified and tweaked front suspension, and a stock sloppy rear one. When I went to the 03 IRS (with 500 miles on it), even with the rubber bushings the difference was night and day. Don't get me wrong, the car's no enzo, but for the money invested in the suspension, it'll open your eyes.

Edit: It just ocurred to me you might be talking about the newer mach1. In which case it would have the same stuff as a GT under it. So why your dad didn't get the gains that the cobra has over the GT is hard to say. It may still need to be set up?

795.0pacecar · Jan 18, 2007

The mach 1 has a vortech supercharged DOHC 4.6, maximum motorsports caster camber plates, bilstien struts, and steeda sport springs. The battery has been moved to the rear.

The IRS just bolts in, there is nothing to set up. In stock vs. stock tests, the 03 cobra wasn't that far ahead of a stock mach 1. (I think it was just over or just under a second faster on a road course) Considering the cobras came stock with better shocks and struts along with the IRS and about 100 more rwhp, thats not incredibly impressive.

A well set up solid rear can hang with the best of the IRS stuff. The only reason I would swap to an IRS would be for the novelty, its something that is different and can be done cheaper than setting up a solid rear to perform on par.

Sicarius428 · Jan 18, 2007

Considering the cost of gears w/installation, 5 lug with cobra brakes and a decent shock and spring a IRS swap is a steal if you are looking for 3.55s out of the 03/04s. It might weigh more than the solid rear but for a fox, the tail is a little too light as it is IMO.
The Cobra might be marginally better than the Mach 1 on the track but the Mach 1 does have a pretty good weight advantage too.
Kevin

carbed87 · Jan 18, 2007

man thats sick, so it just bolts righ up huh, no welding or anything.

Sicarius428 · Jan 18, 2007

Gotta drill a few holes because the rear doesn't have a mounting point on the framerail. Other than that it seems pretty painless if you have an afternoon to spare. Gotta cut the rubber bumper out... this explains it better.
http://www.mouthbreather.net/IRSSWAP.HTML
Kevin

795.0pacecar · Jan 18, 2007

If I found one at a good price I would defiantly get it. I think they look awesome.

Sicarius428 · Jan 18, 2007

Damnit i need my bonus check now!
Kevin

carbed87 · Jan 18, 2007

Sicarius428 said:
Gotta drill a few holes because the rear doesn't have a mounting point on the framerail. Other than that it seems pretty painless if you have an afternoon to spare. Gotta cut the rubber bumper out... this explains it better.
http://www.mouthbreather.net/IRSSWAP.HTML
Kevin

jeebus man! that looks like cake. can you use your stock driveshaft. and it it hard squaring the whole assembly up. i take it if everythings not squared up you'll have major alignment issues lol.

seijirou · Jan 19, 2007

carbed87 said:
jeebus man! that looks like cake. can you use your stock driveshaft. and it it hard squaring the whole assembly up. i take it if everythings not squared up you'll have major alignment issues lol.

Stock driveshaft works just fine, you just gotta take your flange off the solid axle rear and put it on the IRS pumpkin.

They square themselves up, but you're right in that they really should be dialed in. The rear alignment is fully adjustable. I've actually thought about stealing a HICAS system off a Nissan and equipping that just for the novelty factor.

795.0 - We're actually on the same page, we're just seeing it differently. 1 second in road racing, to me, is a massive difference. I've been doing vintage racing now for a few years. Most of the races are 15-20 lap sprints, but if you're a second off the pace. Multiply that by 15 laps.... Just imagine a car crossing the start/finish line, then count 15 seconds in your head waiting for car #2 to cross. To me, that's a lifetime.

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