MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Ford IRS?

Although to date I have not heard of anyone breaking the stock MGB salisbury axle (except Larry Embrey and he had crammed in extra thrust washers to create a "poor man's posi" and broke the spiders), I do believe that I found the limits of it's strength this last weekend. Coming back from running the Dragon, it began to set up a bit of a howl, and over the course of the weekend, including quite a few more full throttle blasts the howl increased in volume and frequency until it left little doubt as to it's origin. Apparently power output in the neighborhood of 300 hp or so is just a bit much.

So although I can swap in another replacement axle as a short term fix, I went on the hunt for a replacement. I abandoned my intention to fit an 8" Ford axle, deciding that a light weight 9" would be far more durable yet not a great deal heavier, but in the course of researching the 9" I came across a site or two using the 9" as the center for an IRS setup, and recalling that I had seen an IRS at the local Ford junkyard, made a trip out there. Turns out the IRS in question was a Jag unit but they also had a number of t-birds and obligingly hoisted one up so I could get a good look at it. I felt either could be made to work, albeit with quite a bit of fabrication, particularly in the case of the Ford. Price for the Jag which was missing the brakes and various hardware was $100, and for the Ford $200. Another look and the Ford it was. I liked the use of a top link other than the half-shaft, and there appears to be enough room to move the inside pivots inward enough to narrow the track the needed amount. Plusses were complete ventilated disc brakes, abs sensors that I may use somewhere else, a strong 8.8" diff, and the driveshaft as well. I brought it home and will begin disassembly as time allows. I would still consider the 9" as a center section but for one detail I discovered, and that is essentially that the price paid for the strength and compactness of the 9" is a 2-3% penalty in efficiency. This would seem to explain it's discontinuance from production.

So I was just wondering if there's anyone who has attempted this swap? From the looks of things I'll have to create a cage with suspension mount points, diff attachment points and body attachment points. The lower control arms will have to be redesigned as tubular units and made a good bit more compactly it appears, and coil over shocks will need to be worked in, or perhaps the occasional air bag. It's an interesting challenge, but I think the stock suspension geometry can be retained, as well as possibly moving the brakes inboard, and positioning the coil-overs to point at the tire patch and mounted in close proximity to the tire. I'll know more in a few days.

Jim
Jim Blackwood

Uhm, why recreate a TON of wheels, when you can use a factory five racing IRS assembly which uses the ford thunderbird as the donor axle. All the prefab work is done for you, and it should fit it with only the most minimal of modifications. The factory five IRS with pin drive option is 54.25" from wheel mounting face to wheel mounting face. Downsides include: gotta ditch the fuel tank. The 8.8 irs pumpkin is 5" longer (towards the back) then our diffs, and they want to occupy the same space as our fuel tanks. A cell in the trunk resolved that issue for me. Wheel offset might be an issue if you don't have 2" to fudge. Otherwise, there aren't really any drawbacks. I have the entire setup sitting in my garage and it goes into the car in 2 weeks. If you want, I'll take a bunch of pictures for you, otherwise check out http://www.factoryfive.com for some pictures. After doing all my homework, this is the best IRS you can get for our cars.

Let me know if you want all the nitty gritty details, as I've worked them all out already.

Justin
Justin

Justin,

How 'bout taking a bunch of pictures and doing an article for the newsletter?
Dan Masters

I had definitely planned on doing that. (Along with a fuel injection article, as soon as I collect the necessary information)

FYI: The factory five IRS with poly bushings in the rear spindles will plant tires VERY firmly with no wheelhop till you exceed 350hp. After that there are ways to eliminate wheel hop.
Justin

I definitely would like to see what you've done, and am sure the readers of the newsletter would too. I can send along some shots of the stock setup as well since they simply cut away the mounting bolts for the cradle and loaded up the whole thing. A few things I found of interest: The stock upper control arm is a stamped piece in the shape of a large curve so that it dips under the unibody frame rails. In fact, the shape of the stamping allows it to sort of sit over and beside the axle shaft so that at full suspension compression the top of it should be about where the top of a tube axle would be, giving clearance below the unibody frame rail. This seems important. I am assuming the axle CV joints allow some lateral movement of the axle since it is not used as a suspension link as in the Jag. In this case it may be possible to move the inner control arm pivot points inwards to get the needed width. I could possibly accommodate the 54-1/4", but I suspect the upper frame of the cage may be a problem and I think I can build one which is more compact. I would also like to move the coil-over farther outwards. It looks like the rear cover is bolted directly to the cage without any isolation. I'm not overly wild about that rear mount anyway and could easily see replacing it with two separate mounts bolting to the cover bolts on either side of the carrier and just sawing off that extension. I'm guessing the upper shock is an anti-torque device as it isn't present on the stock suspension. Good idea, and can be moved to other locations. This thing has some big bolts on it. Retaining adjustability would be an excellent idea, but I'm not convinced heim joints are the answer. All in all though it should significantly reduce unsprung weight. If the brakes could be moved inboard it would do even bettter but I'm not sure how feasible that might be. Maybe tomorrow I'll get out there with the air wrench and take some parts off.

Jim
Jim Blackwood

Jim,
STAY WITH THE 8.8!! There is no viable reason these days to do a 8 or 9" rear over a 8.8 The 8 and 9" parts are now becoming a little harder to find as all the hotrod and drag guys are snapping them up. The 8.8 are VERY tough, right between and 8 and 9" for durability. We have mustang guys (3400-3600lbs cars) pushing out 500+RWHP and are not phasing the rear ends. Plus all the V8 mustangs after about 1984/5 have the 8.8 in them, so the aftermarket for the rear ends is HUGE, any gearset you want is yours, lifewise for posi's, air lockers, mini spools.. I got 3 different gear sets for my 8.8 non of them I paid over $25 with shipping for..

Seriously, if you have a 8.8 IRS I would hold onto it, they are a great unit.
Larry Embrey

On the contrary, you do NOT have unlimited selection with differentials and the IRS pumpkin. You have about 3 options. The stock posi, the stock open axle, and the ford torsen differential. Those are the only known diffs that work with the irs. Any FMS or other brand gearset will work just fine though. I took some pictures of the irs assembly without the diff or axles in it. Just the cage, upper and lower control arms, and the shocks. They aren't great but will give you a good idea of what's there. You're right about the upper control arm, it could be an "issue" with the frame rail, but I don't have a great way of measuring until it's being welded in the car, then we'll find out. I suppose if there's a clearance issue I could have the welder cut out the corner of the frame rail and invert them, kind of like an inside out box. I suppose we'll just have to wait till next Wednesday and see.

Http://briefcase.yahoo.com/bmanetd Choose the folder "mgb v8" and there's a folder inside of there called "IRS pics" with about 5 pics I just took.
Justin

An air locker would be a nice touch, why wouldn't that work with an IRS if it's available for a tube axle? I suppose a Torsen would be a good 2nd choice. How pricey are they? I was thinking swap meet for diff and gearset. Oh, and a T-5 upgrade. Love the way they shift.(WC)

That cage sure looks big Justin. Is there that much room up in there? I guess if you remove the battery boxes and gas tank it helps, but it still looks awfully tall to me. I'd like to keep my battery where it is if I can. I can see where attachment to the unibody could be an issue too. I was thinking along the lines of using the existing spring mounts as a starting point, then perhaps a couple of mounts that sandwich the existing sheet metal. I'd like to avoid welding and repainting. I even considered the idea of a torque tube to the transmission but maybe that's going a bit too far. It'd be a fairly short one though.

Here's a link to some shots I took:
http://edit.briefcase.yahoo.com/edit/blown_mgb_v8/fupload_parent?.dir=/Public/Photos/MG/IRS&.src=bc&.action=upload&.view=l&.done=http%3a//briefcase.yahoo.com/bc/blown_mgb_v8/lst%3f%26.dir=/Public/Photos/MG/IRS%26.src=bc%26.view=l

Don't know if that'll work or not, but if it does maybe one of you could interpret the tag for me.

Jim
Jim Blackwood

To see Jim's pics, go to http://briefcase.yahoo.com/blown_mgb_v8

There is a lip cut in the differential where the axles enter it and not many differentials have that lip cut. The torsion differential is around $500. From the sheet metal above the mgb differential, to the bottm of the differential is 14" From the top of the upper bar to the bottom of the IRS cage is 14 1/4" so There shouldn't be much of an issue in that regard. MGB frame rails are 34" apart above the differential, and the upper cage bar is 32 1/2" wide, so a little spacer between the cage and the bar will resolve that issue. That inch or so of clearance should also allow room for the shocks to go down without hitting the frame rails. The rear "X" bars are 37 3/4" from end to end, and in the trunk those same frame rails are still 34" apart, so a little cutting of the tubes should work just fine. Yes, the battery frame has to go. I have my battery in the trunk with the fuel cell, and as soon as I buy an optima red top, it will be mounted on its side right behind the passenger side tail light. I plan on welding some square metal tubing to the floor pans and tieing it into the rear crossmember (right behind the transmission crossmember) and running it backwards to the open area so I can weld the front of the irs lower cage to that. All this welding should actually stiffen up the car some (connecting the frame rails together) and I'll be looking forward to seeing the results.

Justin

The hole in the stock upper arm measures about 19" from center, meaning the low point is 38" across, center to center. As the hub comes up the link rocks and keeps the low point at about the same place. Luckily the low spot is pretty wide so the exact low point isn't too critical. The overall hub to bub distance is 63-1/2" so the track will need to be narrowed, in my case, to approximately 53". I'll be checking that dimension in a few days. So that's 5-1/4" removed per side. It looks very much like this can be done simply by moving the inner pivot points towards center by that amount, leaving the upper arm unchanged, and making up a new tubular lower arm, but that means I'll have to look closely at the width of the MG frame rails to see how it all works out. I think it'll be OK though. My car sits quite low so I want to position the cage high in the body, or at least have the capability to do so. I got the driveshaft unbolted this evening. Really big bolts on this stuff. I'm going to have to get out the 3/4" drive stuff from the looks of things.

Jim
Jim Blackwood

I had not heard anything about the IRC center section being different than the tube axle center section. I will have to lok into that. There is ro was a Air locker available for the 8.8 I know that much. I would think the torsen would be the best for the MG, very durable and great load sensing will help keep traction planted, $500 is hella cheaper than the rip-off they want for MGB torsens that's for sure..
Larry Embrey

Get out the metric stuff Jim. Most bolts I came across were metric, which I can't figure out. This stuff is built by FORD, not honda, FORD. It's built in DETROIT. Why is everything metric? Did some Ford exec loose a bet out on the putting green and have to sign a contract with a metric bolt supplier or something?

Ridiculous.....
Justin

Jim, it is a singletrack 3.01:1 gear ratio rear end. Hope this helps. If you want a posi...look in SuperCoupes and I believe some Lincolns have an aluminum center section.

Good Luck!

Galen
G.P. Copes

oops...3.08:1
G.P. Copes

We have separation.

The running gear is now disconnected from the cage and suspension, broken sockets and all, but I'm a little puzzled. When was it that I signed on to work on old British trucks? Ford has definitely gone off the deep end. Metric bolts I could understand. SAE bolts would be reasonable. Even a few of each I could manage, but what in God's name ever possessed them to use Whitworth?!!! That's right. All those big bolts that should have been on a lorry? Standard wrenches didn't fit, metric didn't fit. Whitworth. The motorcyle wrenches were pressed into service and did the job. But I felt like I was working on a friggin truck. Cheaters on every bolt, big monster bushings, I even got out the pipe wrench before I was done. If I can't lose some weight with that rig I'm just not trying.

Speaking of which, maybe that aluminum center section isn't a bad idea. By the time this is done overall weight could easily be more than the stock axle and springs. Of course the unsprung weight is the important thing. Still, the yard is bound to have a few Marks sitting out there.

Jim
Jim Blackwood

Yes once again the Metstang strikes!!!

Taking apart the 5.0 mustang for my Fairmont project I ran into the realisation that most of the drivetrain and suspension were metric. front swingarm bolts 15 & 18mm., clutch pressure plate 10mm, shirter retainint bolts 12mm, etc etc..
Larry Embrey

I think I'm on to something with my putting green theory about the metric bolts. There's no other possible explanation, and there certainly isn't a logical one.

Jim if you wanna sit tight by a week or two I'd be happy to be the test monkey here and tell you what I find with the factory five setup. Maybe we can use mine to make another one? I was reading a guys website 2 nights ago and his 5.0L cobra is making 321rwp and he's putting down 12.2's with the irs setup and street legal tires. That's pretty damn nice if you ask me
Justin

Putting green? How does that explain it?

Justin, it'll be a couple weeks before I can actually start building I expect, since I'll have to get materials. This weekend I'll swap out my old axle for another stock unit and investigate the damage. While it's out I'll get some measurements and maybe try to mock up a box or something for the space available. Too bad I don't still have one of the old junk bodies for a mock-up, but I'll take a good look around for attachment points and such.

Also I'll try to remove the half-shafts and get some ideas for shortening them. Should be several ways of doing it but getting the end in a lathe could be a challenge. Anyone have ideas?

Another thing I'd like to consider is air suspension. I saw an IRS on the web, (a 9" I think) where they put a Firestone bag around a Carerra shock. Seemed like a good concept, though presumably even just a plain old air shock could work. How well is an open question, but it'd be pretty cheap to try. At any rate, using the Firestones, I designed a system for off-road that would allow tuning of ride height and spring rate independently of each other but it has yet to be built. May be possible to redesign it for the MG.

Jim
Jim Blackwood

The only thing that could explain such an assinine decision to use those oddball socket sizes is some ford exec bet the oddball bolt guy he could drop the next putt, and if he didn't he'd by 8 billion bolts from him. I think we know how the putt went. A bit of a joke if you will.... heh heh

Measure the diameter of your axles dead in the center. If they're not atleast 1 1/16" of an inch in the center, they'll never handle the kind of power your car will put to them. You really need the 1 1/16" or bigger axle which came on all supercoupes, and some of the later V8's As long as you solid mount the diff into the car, the framework itself should be pretty insignificant. Using nylon bushings in the stub assemblies will pretty much negate all wheel hop. They can be purchased from vintage performance in New York. http://www.vintageperformancemotorcars.com/home.htm

You can even use mustang quad shocks on the IRS, but it's not necessary if you use the nylon bushings.

Lots of good info out there on this setup, and I still believe fabricating/purchasing a cage will be easier then adapting the thunderbird cage.
Justin

Didn't plan on adapting the Tbird cage, it's way large. Instead, build a cage, use the upper Tbird control arm, and build new lower arms, shorten the half shafts and that's about it. Nobody makes a Tbird cage for the MGB body so it's a new design. Tbirds weigh plenty so Tbird bushings with MG weight will be much stiffer than with Tbird weight if I want to use them. For performance bushings I think I'd go with UHMW. (an engineering plastic- ultra high molecular weight poly... something) Come to think of it, there may be sections of the stock cage that are usable. I'll need to have a closer look. You may have something there.

8.8 IRS rears use C clips I bet.

Jim
Jim Blackwood

I wish someone had let me know the axle stubs just pop out of the housing, (spring detent C clip) if I'd known I could have tried fitting the housing up in the body while I had the axle out. As it was, I had the replacement in, bolted up, and the brake lines back on. Taking a break I pulled the cover off the 8.8 and seeing no C clips tried prying the axle out and was much surprised when it popped right out. I'll try to get some photos tomorrow. Anyway, there seem to be plenty of attachment points available, and Justin, it looks like there may be adequate room for your upper control arms. It'll be tight up in there with the battery boxes left in. If the centerline of the axle is left in the same place as it should be then at the very least the battery boxes will have to be notched out for the front diff mounts. Designing the diff cage to handle torque loading will be interesting, a long arm up to the cross member would seem to be a good idea though.

I'll need a standard 8.8 cover to replace the aluminum one, and then there are the brakes. I absolutely refuse to use those on my car, so I guess I'll need to look into other options like maybe the Mitsubishi brakes. The problem with the T-bird brakes is with retracting the piston when changing pads. I've got the same brakes on the wife's Continental and I absolutely hate them. They take a special tool, and even it doesn't do the job because there's nothing to keep the internal screw from spinning. Out of 4 attempts to retract a piston 2 have resulted in a torn seal and required full seal replacement, and the seal kit is expensive and hard to find. The Mistubishi rear brake caliper on the other hand is a very fine piece and the piston is easily retracted.

Does anyone know how the ABS toothed wheel is attached? Pressed on I would guess. I'm thinking it might be possible to make up a spider to press on there and weld it in three spots to the CV housing, then bolt a brake rotor to that, either something like a Willwood or perhaps a motorcycle rotor. I don't think it would have to be all that big. Then use the Mitsu calipers with that. That leaves the hubs and their aluminum carriers pretty light.

Next question, does anyone know the proceedure for removing the half-shaft from the carrier bearing? It looks like I probably do have the 1-1/16" shafts.

Jim
Jim Blackwood

Oh yeah, no c clips on these axles. They just come right out! I spent the day out playing on my car instead of fooling around on the computer. Had I saw that, I would have given you the heads up. I figured it would be a darn tight fit with the battery cage in there, and that's why I ditched it. If you want, I'll measure out my framework and e-mail it to you so you'll have something to start off of. I think the two pieces of square tubing welded to the floor and going back to the diff cage should work quite nicely. If I go really mad, I can put in square tubing perpindicular to those, and parallel to the crossmembers, and "box in" the back section of the floor pan. That should really strengthen things up. I'd be afraid of using the housing bolts as mounting points for fear of oil leaks. Can they handle the kind of stress they'll be facing?

Rebuilt calipers are $34.00 each at Autozone. Sounds easy enough to me...

Are you talking about removing the cv joints, or removing the shaft itself from the stub assembly? I put a 3 jaw puller around the wheel hub, and just pushed it back out. No big deal at all. If you're talking about removing the cv joints, I have some tricks for that too. I'll dig up the links to the websites that show how to do that.
Justin

My idea of changing brake pads is to swing the caliper out of the way, crank the piston back in, slap in new pads and go. No changing calipers, no messing with brake lines or cables, no replacing seals that got torn by the piston. It should be possible to do this at least once between caliper replacements and preferrably 2 or 3 times. These Vargas calipers are a poor design in this regard because the internal screw that allows an integrated cable brake freewheels when you try to spin the caliper back in because of the mechanism that allows the screw to advance to compensate for wear. About half the time you get lucky and with a great deal of spinning manage to get the piston retracted. About half the time all that piston spinning trashes the dust boot. As I recall the Mitsu caliper has an external socket head screw or some similar arrangement, as clearly they recognized the problem and fixed it. I'll not knowingly put a defectively designed part on the car when there is a good alternative.

Those two tubes up either side of the transmission tunnel are a good idea and I think I'll do that too. That provides a very long lever arm to transfer torque from acceleration and perhaps braking, and will really stabilize the whole unit. That and a bar across the top tying into the shock mounts and possibly the bump stop attachment points and/or the limit strap hangers should do the job. Other options would be to tie into the front spring hangers. My car doesn't have the swaybar hangers but that might work very well.

I'm not anxious to jump in and modify the fuel tank, and relocating my small tank for the EFI would be a pain, but what really makes the most sense would be to buy a new fuel tank and weld a swirl pot/fuel pump assembly into it from the top and then see what can be done about the battery. Those boxes add some stiffness too, so that needs to be looked at. If I wanted to I could add several gallons of fuel capacity by widening the tank into the area no longer needed for a muffler.

As far as mounting to the housing cover bolts, the correct way to do that is to cut a piece of plate (7 or 8 ga. should be fine) to sandwich between a stamped steel cover and the housing and extending past the flange far enough to weld or bolt it to the cage. That would easily be as stout as the aluminum cover/mount. It should attach to the top tube at the top and possibly the sides and to the long tubes at the bottom. The real question here is where the isolation mounts go, since they could be located either where the plate attaches to the cage or where the cage attaches to the car. I'm pretty sure bolting the diff up solid to the body will cause noise.

Let's say the cage gets mounted solid to the body, then the rear plate can't be used as a means of joining the long tubes to the upper cross tube and redundant structure is needed. OTOH, if the diff plate is made structural, solid mounts should be used at the front, and the entire cage needs to be isolated. This should be the lightest construction, but means more flex points between the wheels and the body and also means having to isolate the cage at the front of the long tubes (I think you were going to weld these to the floor), at the shock mount points, and elsewhere. Bushings for the front spring mounts are available. However, the diff mount plate could be bent at the sides to make a very rigid vertical structural member. Of course, Ford had isolation at *all* of these points.

I will need to disassemble the CV joints. I separated one of the inner ends but haven't cleaned it up yet. I suppose the rollers are held on with clips or something? I have no idea what it takes to get the outer ones apart. As for the axle nut, why does that look like it's wrapped with sheet metal?

I'll be looking at it again today.

Jim
Jim Blackwood

A lot of the cobra guys are solid mounting their diffs to the cage, and the cage to the car, and no one has complained about noise yet. I don't think it needs to be separated from the car. In fact, a lot of people replace the rubber front mounts with aluminum ones so the diff doesn't "shift" during spirited driving. FFR went with two mounting points and haven't had a problem yet. The front of the cage, and the X pipes at the top, back of the cage. Those guys put a TON of r & d into these cars, so I'm going to trust them on that one. In fact, when they came out with the IRS it was part of a package that went together with a 427 big block ford, not the typical 302 driveline. It was designed specifically for a 427 and all its power and torque. Once again, If they've done it on a few thousand cars and no one is complaining, I'm not about to start. Here is a forum thread regarding the removal of the cv joints, I found it to be incredibly helpful.
http://www.ffcobra.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=008945

Here's some pictures of someone putting the IRS into their car, so you can get a better idea of what all is there.

http://thevenom.net/cobra/irspics/irs.htm

Justin
Justin

Who makes the slick shortened axle shafts? I may need a pair of those.

Certainly a solid mount makes for the lightest and most rigid solution. Can't see it being totally quiet though.

The Cobra cradle appears to be attached pretty solidly to some beefy looking structural members and attachment points are spread pretty far on both sides of the gearbox. It's a good design for that type of tube frame. I still don't like no rear cushion but apparently it works. Attaching to the MGB front spring mounts and shock mounts would be pretty comparable, and perhaps the upper coil-over mounts could tie into it or the other attachment points up there. That would give good stability in all directions, especially if using the long tubes up to the crossmember, and it's convenient that it has 4 threaded holes in it. The whole cradle could be made to bolt into place. Of course, if the weight could be distributed to the shackle points as well it would be better in terms of maintaining body alignment, but that's getting a bit more complicated.

I've got the car back together except for gear oil so there's no particular hurry on this end. I would like to see what you end up with.

Jim
Jim Blackwood

I have a 1989 Cougar XR7 with the aluminum rear center-section. It is basically the same car as the T-Bird SC. With the intercooled & supercharged 3.8 V6, aluminum traction-loc IRS rear end, 4-wheel disc brakes, sport select suspension and a whole lot more!
All in a 123,000 mile So. California car with everything working great except for a slightly blown head gasket. Absolutly no rust or damage. Current registeration and smog, runs STRONG to 145 mph. I'm offering it for sale, $2000. Marc, Los Angeles (2 midgets, Rover SD1, T. Stag and a few others)
Marc Judson

I have a 1989 Cougar XR7 with the aluminum rear center-section. It is basically the same car as the T-Bird SC. With the intercooled & supercharged 3.8 V6, aluminum traction-loc IRS rear end, 4-wheel disc brakes, sport select suspension and a whole lot more!
All in a 123,000 mile So. California car with everything working great except for a slightly blown head gasket. Absolutly no rust or damage. Current registeration and smog, runs STRONG to 145 mph.
I'm offering it for sale, $2000. Marc, Los Angeles (2 Midgets, Rover SD1, T. Stag and a few others)
Marc Judson

Must have been a bad day on the links. No doubt it started off innocently enough, maybe nothing more on the agenda than insuring a supply of those fancy axle nuts with the captured washers, but by the end of the 19th hole it appears the Ford exec had the weird bolts supplier firmly in his pocket. His back pocket that is. Not only had that missed putt cost him the whitworth heads on all the large fasteners, but he now had some very nice adjuster bolts with winged shanks which required special rotating offset bushings to use, and to hold the splash shields in place, where a couple of 6mm bolts or even self tapping screws would have done the trick he now had three of these very trick 10mm dog pointed, flanged hex head torq's socket, loctite pre-treated and zinc plated bolts that were going to cost him a fortune. No question about it, these puppies were going to do a fine job of holding the tin in place. If it didn't rust off, bend, or crack around the bolt heads that it. But at least the bolts weren't going anywhere.

Jim
Jim Blackwood

I hated those three damn bolts holding the mud guard on the hubs. I fought with them and ended up destroying the shields in the process. What a stupid ass design they used on most of that assembly. I'm gonna stick some allen headed bolts back in there so I'll actually be able to take it apart again when I need to.

One of the neat things about the cobra irs frame is it's 2 parts. The main cage, and the top bar. The top bar has the mounts for the coilovers attached right to it, and the mounts for the upper control arms. What if you went that route, and made the cage 2 separate parts so you could attach both of them at the best strategic spots without really compromising anything? In my case I'm welding into the frame rails right above the diff, and also the frame rails inside the trunk. And the torque bars under the floor. If you made a plate to mount to the back of the diff and ditch the thunderbird cover, you probably could keep the fuel tank right where it is, and just mount directly to the frame rails both in front it, and behind the differential, and the torque bars jutting out from the floor. That should be pretty secure?

Justin
Justin

I would imagine. I've been thinking about a bolt-on configuration and I think everything is there for it. Still up in the air over whether to cushion the attachment points or the diff but I'm leaning in the direction of the diff, as a sub frame bolted in solid would strengthen the body and could be welded if desired. It would also replace the bracing lost in cutting out the battery boxes. And you are right about the tank I think. In my case that still means modifying the tank for EFI (should have done it that way to start with) and finding a spot for the battery.

I used heat on those bolts. The ABS rotors are press-on, I'm thinking about getting a quote for Wilwood rotors to bolt to a pressed and welded spider, but also still looking at bike rotors. They need to be 10-1/2" by .390-.330". Priced Mitsu calipers, they're a tad steep at $70 ea. (plus deposit no doubt). Probably would hang the caliper from the cage. No need for flex hoses anyway. Shouldn't be any need for the shields either (Hooray!). The hubs are nice and light without the brakes.

Jim
Jim Blackwood

<<Most bolts I came across were metric, which I can't figure out. This stuff is built by FORD, not honda, FORD. It's built in DETROIT. Why is everything metric?>>

Justin,

They've been slowly using more metric fasteners for many years. You can find 'em on U.S. cars & trucks over 10 years old. The only cars that I own that aren't metric are my '68 Camaro and my '79 MGB. My '00 Silverado? Metric. It's hard to sell products to the rest of the metric world without conforming. Besides, a big percent of that Ford is sourced from outside the U.S.

The Federal Go'vt started us down this path with the Metric Conversion Act of 1975.
Carl

That's perfectly reasonable Carl, but give me a reasonable explanation for the Whitworth heads? The car's not even British for heaven's sake!

Jim
Jim Blackwood

I've hit the first major hurdle for this modification. That nice cast (or probably forged) aluminum bearing housing whatever you call it that the control arms attach to needs at least 7" from the hub flange to the back of the top knuckle, and should have a half inch more for the brake rotor and clearance. It sits about 6" above the axle centerline and at full compression would be in about the same location as the bulge that the bump stop is bolted to. Being optimistic, there might be 5" of clearance between the MG hub and the body at that point so this presents something of a problem. I'm not sure what the solution is at this point. I don't see raising the ride height as a solution, and I don't think wheels with a 2" deeper backspacing are the answer either. I'm not ready to cut the body, so I intend to have a closer look at those aluminum bits. Maybe there is another part that will do a better job there.

Jim
Jim Blackwood

So you're saying the top knuckle of the spindle will be in the same location as the bumpstop when fully compressed? Or are you saying it will want to occupy the same realestate as the metal the bump stop is bolted to? If it's the former, sounds easy -- remove the bump stop. If it's the latter, then that could be an issue, one I hadn't seen either. I measured my assembly from the back of the top knuckle, to the back of the other top knuckle, and I get 39" on mine, with mgb frame rails being 34" apart on the inside. Not knowing how wide those frame rails are (2"??) that would put 38" from outside to outside, and I've got 39 -- lil too close for comfort if you ask me! And that won't leave much room for my upper control arm to move. Maybe I'll have to dig out the bfh, or let the welder fix the problem for me...

My frame goes in a week from this coming wednesday, but I'll be sure to get some good measurements for you before I get it all in there.

Justin
Justin

I appreciate it Justin. If your car is using RB ride height you may be OK, but on mine I'm pretty sure it'll be a real problem. I'm considering fabricating a set of billet spindles to move everything outwards, but that would be difficult with outboard brakes.

I also found out yesterday that Ford had decreased the size of the bolt circle for the wheels on the T-bird. GRRRR.... Now I'll have to redrill the hubs.

And I need to find out who makes short axle shafts.

Jim
Jim Blackwood

I bet moser could make the axle shafts no sweat. http://www.moserengineering.com I have a connection for a guy out in spokane washington who can redrill the hubs. I called everywhere and no one wanted to do it. Let me know if you have problems finding someone to drill them. If you're going to a 5 bolt pattern it's not so bad, but if you're switching to a 4 bolt pattern you need to cut the studs off in their holes, tack weld them from behind, and then drill.
Justin

I sent them an e-mail. Their prices look reasonable. My bolt circle is early Mustang, 5 on 4.5" so it was a bit of a shock to find they had made it smaller. I will probably end up re-drilling them myself, but that was just another unexpected complication. However, the good news is that the replacement axle is nice and quiet and should serve well for quite a while if I don't abuse it too much. This also means my T-50 is still doing fine. However since driving Ted's TR6 with a WC T5 I just can't forget how easily it shifted so I'll be in the market for one.

I'll need a chunk of aluminum 2-1/4 x 10 x 20" to make up the new spindles. Probably a C note or so in material costs. I toyed briefly with the idea of having the local tech college cast a set for me, but for the trouble of making a mold I can carve them out of aluminum stock. We rent from a shop with a waterjet cutter so that's a quick and easy (though not cheap) solution.

I fired off queries to a half dozen or so brake companies to try to source some rotors. Hopefully I'll get a positive response. I'd rather not have to cut down Eclipse rotors to do it.

I had hoped that this swap might lend itself to putting together an upgrade package. I'm beginning to doubt that will work out now and there is probably a better choice. I had been told about 20 years back that a Datsun 280Z IRS would work. Not being familiar with that car I do not know. One thing about it though, it certainly should be strong enough.

Jim
Jim Blackwood

I chose the factory five because ford is still making components for this system, and short of a few odd ball parts (the spindles) everything else is still being used on cars today. 20 years from now, Parts might only be 20 years out of date, as opposed to 40 years out of date with things like the jag, or possibly the nisaan irs setup. That doesn't appeal to me very much at all. Jim, with as wide as your car is, why can't you get the spindles far enough out? Maybe changing wheels to ones with a different offset will resolve this problem for you a lot easier then you're suspecting it will be?
Justin

Jim,

One of the positive aspects of the Nissan IRS is that the PCD is the same as that of the MG, 4 on 4.5.

Justin,

Choosing a different offset to handle a two inch too wide rear end worked for me on a non-IRS diffential because all I had to do was mount MG spring perchs at the proper spring width of the MG spings on the Ford rear end. With IRS, however, the linkage hookup may prevent this approach, but it is certainly worth investigating.
George B.

George, that would be true. I understand the diff housing is fairly long but I'd gotten the impression it would go in without cutting the battery boxes. Of course, the 8.8 would be stronger.

Justin, also true. Generally, newer parts are a better idea. Here's another tidbit. The Mark used an aluminum housing, and it also used a 5 on 4.5 BC I am almost positive. I'm using a Mark space saver spare because it is on an aluminum wheel, takes little room, and looks good. Had I only known...

I do not want to switch wheels. I have the wheels I want, and I like being able to rotate the tires.

I disassembled the hubs and sketched up a pattern for the waterjet cut today and dropped it off for an estimate. It's a pretty simple part, only 2 bores will have to be machined and 2 holes drilled and tapped. Most of the work will be done with the waterjet, and it should be a good bit stronger than the stock spindle and about the same weight. It'll let me move the control arms out about 3-1/2" and move the coil over's out nearly that much as well. With a tubular lower arm unsprung weight is going to be way down and I think I'll be able to use the stock length and geometry for the arms. I'll use the stock bushings as they will be plenty stiff for the lighter MG, but the lower outside bushings will go in the control arm rather than in the spindle. My one concern is making sure it will all fit inside the 14" wheel. It may be a little close on the top knuckle.

Jim
Jim Blackwood

Moser does not make axles for IRS. Any other tips appreciated.

Jim
Jim Blackwood

I've decided to build up the spindles out of steel tubing. The aluminum plate was as expensive as the waterjet cutting and I'm trying to keep expenses down on this in case anyone else is interested in doing it. The pieces made of steel tubing will be as strong as the aluminum ones and just as light, and they will cost a whole lot less to make so it makes a lot of sense to go that way.

Jim
Jim Blackwood

This thread was discussed between 06/05/2003 and 30/05/2003

MG MGB GT V8 Factory Originals Technical index

This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.