Art Morrison IRS, 73 Camaro
 

We recently finished the install of the new Art Morrison Enterprises IRS in Mary's 73 Camaro.

Unlike their First Gen Camaro IRS, the second gen install requires a fair amount of cutting to get it in there. Second gen's have the rear seats pushed as close as possible to the rear axle, the frame rails are vertical just ahead of the axle which poses clearance issues to the toe links. The first thing to install is the 2x4 cross-member. I chose to raise the floor to the top of this cross-member which made room for the mufflers. I added frame rail sections inside the rear seat area on top of the frame rails to beef up the strength lost by cutting away the rails in the toe link area. The new rear floor follows the reinforcements.

FEATURES
Center diff from Strange, based on Dana 60 internals. Ratios from 3:55 & lower, OR use a stock fifth gen Camaro diff.
Axles are Drive Shaft Shop, good to 1400hp.
Fifth gen outer axle carriers machined to take ZR1 HD hub/bearing units this gives you a GM bolt pattern, the Camaro has a slightly different wheel stud spacing. The Corvette hub has a larger center register than a Fifth Gen Camaro.
Stock fifth gen brakes work depending on wheel size or Willwood & Baer have 14" 6 piston brakes for it that should clear 18" wheels.
Adjustable toe-steer in turns.

INSTALLATION:
1. Mock up the IRS in the car with the frame brackets bolted on.
2. Center the wheel in the wheel arch, check for square.
3. Tack the frame brackets to the frame, (reinforcing plates should be welded on first).
4. Remove IRS then fully weld brackets.

A 2" x 4" cross-member must be installed by cutting through both frame rails, it extends pinch weld to pinch weld. There is a raised area in the floor pan that the cross-member sits half in and half into the rear seat area, so the floor pan has to be cut from the crossmember rearward. I also had to cut out the trunk floor from just above the fuel tank anchor points running 10" forward. Also the corners of the trunk drop-down needed to be cut back on an angle to allow access for welding on the frame rail reinforcement plates and cradle mounts.

New IRS
NOTE I quit Photobucket when they started charging too much so many photos are not available. I'm uploading new pics here but I don't have all of them, but Mary does.

Tie rod just clears what's left of the frame rail, only about 3/4" left, which I plated over on 3 sides with 10 ga cold rolled steel.


Note frame rail reinforcements left and right Floor is raised about 2" & slopes upward sooner. I should have cut out the tunnel straight across and made a whole new one.
I wasted a lot of time cutting out the old seat belt holes and patching them, the lower edge was not flat where it meets the new floor pans so lots of work there.


Left and right sides are the remains of the factory floor pan contour. The front cradle mounts are about an inch below the new floor, allowing installation from below by one person. The rear mounts have fairly good access by cutting off the trunk floor corners and using a Ricks gas tank with trimmed corners similar to the DSE tanks. This gives you a space to reach up and install the nuts.








welding the exhaust


Trunk filler panels

Thanks for the insight David! :thumbsup:

How's the weight of the system compare to the conventional axle and leafs?

New Baer 14" brakes & Ride Tech coil over Triple adjust shocks


http://i117.photobucket.com/albums/o...psjupt7m7p.jpg

http://i117.photobucket.com/albums/o...ps004786b5.jpg

Alignment
http://i117.photobucket.com/albums/o...ps7991bc64.jpg

Videos: if you click the link, you may get a better quality video.

Autocross run:

https://www.youtube.com/watch?v=S-nhjVa5V4M
Popular Hotrodding video


Suspension cam:

https://www.youtube.com/watch?v=L6oz...ature=youtu.be

unbelievably cool. Interested what your thoughts are on how it drives compared to the solid axle. I wanna see a 2nd gen with a tiny bit of negative camber on the rear!

Awesome Dave! Was hoping you would post this up. :popcorn2:

It's way better right out of the box! Sure footed is the best description I can give of it. The car isn't upset as easily and the street manners are outstanding!
Mary has done two local autocrosses and one in San Diego where she won the new SCCA Tour CAM (Classic American Muscle) class.

Very helpful info David.

Feel free to post much, much more on the subject.


:thankyou:

Awesome stuff.

Very nice. When you can share, I would be interested in your thoughts on the roll center height versus spring rates and whether you are running any toe steer with bump.

Pappy

I don't have the roll center height data but they say it's very stable which is the main consideration, it moves 1:1 with the body.

We are starting from scratch on spring rates and shock valving. The motion ratios are different from the stick axle we had, more like the front now. We are at 450 in spring rate which is what Morrison runs on their 69 Camaro. It works very well, I doubt we will be far from that in a year from now, but time will tell.
We started with an aggressive toe steer setting (toe out in bump) we found that to be too much and backed it down to pretty close to what Morrison runs on their 69 right now. We will experiment further.
I'm not much up to speed on the "numbers" yet, we have been so busy just getting it into the car. I'm not sure my Performance Trends software can even handle this type of suspension. I kinda doubt it.

Thanks David. Great to see a straight up review.

How's the First Gen coming? I think we need a project thread on it :thumbsup:

Thanks David. I use Performance Trends for various IRS designs. The data enters like a double a-arm front suspension with X,Y, and Z measurements of the pivot points. It will yield moment center, instant centers, camber gain, and the like. I am anxious to see Mary's car perform in person.

Pappy

Ron,
I have my rear IRS in the shop for my 67 Camaro & will begin the install within the next week. I've been told there is very little cutting needed compared to a second gen. My engine should be done in a month so I can start building my headers then. It's a tall deck RHS block. I think I'll get it running before doing the body work, then finish the fenders to suit my wheels and tires, then tear it down over winter and paint it. Autocross is ending at Marina by the end of the year and I'd like to run the car a few times locally & work on the setup before I have to start towing longer distances to events. If I don't get it running by late year, I'll just paint it, then run it next year. I'd love to have it in good shape for the USCA events next year.

I'll start a project thread when I make some progress on the IRS install. Not much to see right now except the junk I'm throwing out/moving in my shop, I'm making room so I can move my Camaro around.
The nice thing is, our cars will be the same under the skin, Although I'm running the LG drop spindles and Mary isn't.

Morrison recommended I get new frame rails with my IRS. They make their own first gen frame rails. The assembly comes as shown below and I was advised to fit it in the car as a unit. They recommend cutting out the factory frame rails but leaving the spot welded flanges in place. This gives a thicker area to weld the new rails to. I'll sand blast the stock rails before cutting. The paint on Mary's frame rails was tough to remove, it's whatever JCG used.

The suspension comes aligned so you can measure from the hubs to the fender openings to get it centered up.
My IRS:

That's encouraging, I have to get all the measurements for it.

HOLD THE PHONE!

WHAT?!?!?!?!?!?

I'm speechless. What an intense set up. :thumbsup:

FAA is tightening security. I guess Autocrossers are a risk. There is SO little going on at that Airport it's pathetic!

What a load of crap!

What's left? Oakland, GG Fields, SJCF and Mather?

I haven't been down there in over a year but $1 to a bag of donuts there are houses going in near that parking ramp sometime soon if construction hasn't already begun.

I can't figure out how to get ahold of Jesus Villareal, thinking maybe you and Mary know him. At any rate, Tesla now runs the old NUMI plant in Fremont. They aren't using the big North lot. Might be a chance they'd be amenable: https://www.google.com/maps/place/45...6e26a14c243e97

Pacific rail depot in Milpitas (pretty sure this is still in use though): https://www.google.com/maps/place/65...8e66bfd64ef337

Also in Fremont, this lot isn't far from NUMI and IIRC used to belong to NUMI as well. Access appears to be via the wrecking yard property to the North: https://www.google.com/maps/place/67...6db48f4e2af05f

The holy grail is of course Moffett Field. Now that Google runs it perhaps there might be a chance?

Marina city wants us, FAA which is federal does not. The city makes some money off autocross, FAA doesn't make a dime & could care less what we want.
Houses will be built closer some day, but it's a long way off.

Hi David ,

looking for some expert advise.

I want to build a first gen camaro next year.
What would you recommend for front suspension to best match with the Morrison IRS.

Project will mainly be used for street / highway very occasional track day, we don't have as many autocross events as you guys.

How is the Morrison IRS price wise compared to the RS Fast track IRS.


:thankyou:

John

We are using the Morrison front sub for both Mary's 73 Camaro, my 67 Camaro, and James Shipka's One Lap Camaro (67) OLC has the Lateral Dynamics 3 link and he just ran at the USCA event at Laguna Seca. I'm sure he will agree the car is the best it has ever been. The IRS will work with any front suspension you choose, even stock, but on a First Gen Camaro, the extra tire room an aftermarket sub provides is a big improvement in getting adequate rubber up front.

Here is a quote on pricing from Craig Morrison that was posted on Pro-Touring.com

Very cool set up.:thumbsup: :thumbsup:

David / Matt,

As delivered, these setups do not come with any sort of powder or other coatings, correct? Is that an option, or is it left up to the customer?

What is the estimated time of delivery for a complete setup?

THanx,
Bryan

I think they can coat them but generally discourage it's likely to get scuffed when being shipped. They strap the sub down with metal bands which could leave marks. The crates are awesome but the sub could get scuffed regardless.
I would guess delivery would take a little over a month, but you better get an answer from Morrison on that. They would have to order the Diff & Axles from Strange and the Driveshaft Shop so that needs to figure into the time it takes.

99.9% chance they won't coat anything they send. To many issues with doing so.

I got to see Mary's Camaro in action last Sunday at the autocross in Marina--it was awesome. What was weird was how much more it moved like a newer Corvette than an old track car. The body and wheels were in constant motion (independently), and yes, the car stuck like an angry !@#$%.

What was fun was relaying Mary's time to a kind of intense guy who runs a GT2 or GT3 Porsche (with slicks). He was in chronic disbelief, and I quite enjoyed reassuring/informing him of what he'd witnessed. He was not beating the old Camaro...

I was glad to finally run the Marina course, and it sucks to hear that it will be gone soon (I've heard the same about Mather, with only two weekends this year). After doing Goodguys on Saturday, Marina felt like a giant truckstop--totally awesome contrast. With all the room, I couldn't figure out where to put my car ('cuz I suck, and have nil auto-x experience); I might have done better pulling my car on the trailer, and I still wouldn't have hit any cones.

That's great news. Hoping Mary will kick some butt this season.

AM Triangulated 4-Bar
 

Hi David,
It has been awhile since I have been on the site but was really excited to see what you have done on the 2nd Gen IRS installation. There was little info out there on what is involved. Your posts are a breath of hi octane fuel with great pictures!
I have been sitting with a AM Rear sub frame project for a year or so trying to decide if I am capable of tackling its installation. I have the AM front subframe, DSE tubs. My buddies have told me to not tackle it and go another route. Well, your pictures while a different install have some help clear the air on what is involved. Many of the same challenges I expect I will have. Thanks a bunch for taking the time to post them.
I expect I will have to completely cut out the frame rails, raise the trunk pan, fab up the floor similar to what you have done inside. Lots of work but looks doable to me now that I have seen some of what is involved.

Good stuff Dave!.. that IRS looks killer!.. ;) can't wait to see it run on the track!
Sucks about Marina.. hope I can get mine finished up soon to get a few runs in.

Not fair putting Mary in the video's. She could drive a horse and buggy faster then most of us in AWD super car :)
Matt kicked ass on this. Now I want IRS :headscratch:

Mary's car is developing well. We found changing rear camber alignment requires a re-set of rear caster. If the clocking of the rear hub carriers (aluminum castings) changes at all, the toe link height changes, and the toe steer can go wrong, we spent the first few events with it toeing in instead of toeing out as intended.

The car feels great now, like a Corvette, which is what we wanted. The rear doesn't get upset so easily like it did before. We really notice corner turn-in is very good.

I'm now installing one in my 67 Camaro: http://www.pro-touring.com/threads/1...tall-67-Camaro
David

Awesome Dave. Be great to see some pics. Been awhile since I've seen it.

One option that was discussed with Art Morrison early on, was to replace the stock frame rails with first gen Camaro frame rails. I opted to retain the stock rails thinking it would be less work and less cutting of the car. Since it was a nicely finished car, I didn't want to do any more cutting than necessary.

Looking back on it, I would have come out with a better finished car if I had replaced the frame rails. The car would have been stronger and it took a lot of time to make up the plates and weld them in. One area that is tough to work on is where the stock frame rails turn upwards just ahead of the rear axle. There are factory overlapping flat plates welded to the floor there and they are sealed with a tar. Cutting or welding there is going to be tough because it will melt the tar and it'll burn. The frame rails would have to stick up into the car almost completely in that area. The area just ahead of what is marked "trunk profile" would need a little filler plating to support the trunk floor.
David

First gen frame rails in a second gen Camaro.

Very interesting, thanks for the information.

We're doing a 5th Gen IRS in my 73 Camaro... well, I guess that's the Royal "we" as I am just driving it out to Scott Mock for him to do.

I like their lower adjustable control arms. I bought all DSE upper stuff, but can't find a 5th gen lower. I wonder if an an AME would fit it.

Here's a video on the Super Chevy Magazine test of Mary's Camaro:
I think it will be in the January issue.

Fixed it for you Dave. Watched it earlier on Facebook, great video and you've got to be very happy with how the car came out. :thumbsup:

That Super Chevy test was the first time I drove her car on track with the new IRS. It was very stable & handled all the horsepower I could throw at it.

A properly setup IRS rides and handles great, and usually isn't as upset wth bumps and transitions in cornering. Looks like Morrison designed a very nice setup.

Very nice! Dave are you guys going to Sema and the shot out with Mary's car? If so good luck!