Slow Car Fast
LIFE OF A GT
December 4, 2008 - Time to do a test-fit of the suspension.
In order to get it in approximately the right place, I'm going to set the lower control arm up so a line drawn between the inner and outer pivot points is horizontal. Most people try to set the arm horizontal, but it's the pivot points that matter. So step 1 is to figure out how high they should be off the ground.
I attached an upright to a wheel and measured the distance from the ground (approximately 8.5"), then figured out how high the car was jacked up (10" above normal ride height). So I want my pivot points 18.5" above the garage floor.
entry 90 - tags: suspension
December 4, 2008 - I can't lift the subframe quite as high as I'd like without cutting something, but here's an idea of the location.
Pretty good, actually. That rear mounting point should actually attach right to the bottom of the stock frame rail. The rails converge and rise in the engine bay, where I need them to spread wider apart. This is going to go fairly well, I think.
entry 91 - tags: suspension
December 4, 2008 - Of course, what I really wanted to know what how the wheel looked on the car.
Would my painted Miata wheels suit it? How far would it stick out of the fender well?
The answer is that it looks good. I like it. The tire diameter is 23" instead of the stock 24" on the MG, but I can probably live with that. I can run a 205/55-14 RA-1 (or some similar R-compound) to give me good traction without having to use a ridiculous tire size, and a 225/45-15 is a future possibility. The fact that I have a set of the RA-1s on these wheels in this size already is just icing on the cake.
entry 92 - tags: suspension, tires, wheels
December 4, 2008 - The tire does stick out a bit.
About as much as I'd expected based on my measurements, which is reassuring. A rough test fit shows that the Rabbit fender flare covers it almost perfectly. I'll pull one of the RA-1s off and test fit with that as well, but I have a good feeling about this - as long as I stick close to the stock +45 wheel offset, anyhow. I should probably make sure the +30 wheels with 205/50-15s fit, as that's what half of my race tires are.
The fairly radical camber is because I assembled this suspension out of spare parts and everything's just finger-tight. No attempt at alignment has been attempted!
entry 93 - tags: body, flares, wheels, tires, suspension
December 4, 2008 - Okay, I should stay away from that combination.
A +30 offset wheel with a 205/50-15 sticks out 3/4" further from the body. As the math says it should - there should be 20mm more when compared to a 195/60-14 on a +45 wheel. The flares don't quite cover them with room for wheel movement. That's okay, I can run a greater offset. We'll see exactly where the flares end up when they're welded in.
I pulled the rear axle off as well. There's a lot of room under there now!
entry 94 - tags: body, wheels, tires
December 6, 2008 - My secret weapon has arrived!
It's a plastic LS1 from P-Ayr that I picked up from Summit Racing. It weighs next to nothing, letting me pop it in and out of the engine bay easily instead of humping around 500 lbs of metal. All of the factory mounting points are represented by steel inserts, so I can also use this to work out my header setup as well as things like motor mounts. If I wanted, I could even install different heads. There's no plastic version of the T56 transmission yet unfortunately.
Most importantly, this lets me experiment with fitment without taking the Camaro apart quite yet.
It was expensive enough that I'm taking very good care of it, and I should be able to resell it after the build is over. Meanwhile, it's going to make life a lot easier.
entry 95 - tags: engine, replica
December 6, 2008 - The engine is in!
And there you have it, an LS1 in an MG. Wow, that was easy.
Okay, maybe getting the complete functioning engine with transmission and suspension might be a little more difficult. But still, the first test fit, fits.
I've got the engine positioned to put the shifter in the same place as stock. Actually, it'll end up maybe an inch further forward. This is the best I can do without actually cutting anything other than removing the motor mounts at this point. With the Miata subframe in place, I should have a decent amount of room for headers.
entry 96 - tags: engine, replica, test-fit
December 6, 2008 - The engine height was set to put the oil pan at or slightly lower than the frame rails.
This is a bit of a guess, but I think it'll work nicely. I might be able to sink it down another 3/4" or so.
With this positioning, the engine ends up in almost exactly the same position relative to the wheels as the Miatas we do at Flyin' Miata. Only the front pair of cylinders are ahead of the wheels and the height looks to be the same. This means I could use an off-the-shelf subframe. Wow, could it be that easy?
The threaded holes in the plastic engine mean I could simply bolt up the extra oil pan. I like this thing more and more...
entry 97 - tags: subframe, engine, replica, test-fit
December 6, 2008 - A test of the hood clearance will have to wait until I get an intake manifold.
There's one on the way right now. As with a number of the other parts, it'll probably get sold after the swap as I won't need it anymore. But placing a ruler across the edges of the hood opening looks promising. We'll see.
I might be able to push the engine back slightly, which would have a beneficial effect on the weight distribution. But again, given where it sits relative to the Miata and the extra weight of the coupe body in the rear - I think it will work pretty well here.
This picture also shows the huge amount of room I'm building in. There's about 3' of clearance all around the car with my work area up front. This is definitely a home project!
entry 98 - tags: engine, test-fit, replica
December 6, 2008 - These spare parts are left over from a Miata conversion.
They'll come in handy with my engine test fits, although I don't have a way to mount the crank pulley.
entry 99 - tags: replica
December 8, 2008 - The complete engine.
No, not mine. This is a 480 hp crate LS3 with a hot cam from GM Performance Parts. Yes, 480 hp. The Miata that's getting this is going to have more than 50% more power than our little MG. Yowza.
entry 100 - tags: engine
December 8, 2008 - Here's a new T56 to go with that LS3.
It's the same transmission as is in our Camaro donor, so I'll be using it for measurements.
entry 101 - tags: transmission
December 10, 2008 - The intake is here!
The ruler test shows that it doesn't really fit under the hood - but the hood isn't flat. Still, I'm hoping to get the engine a bit further down and back. I really need to borrow a transmission to try it for clearance. I think what I'll end up doing will be to strip the interior, cut out most of the tunnel and then rebuild to clear the trans.
entry 102 - tags: engine, fitment
December 10, 2008 - Before I spend too much time obsessing over the engine, I need to get the car's suspension in place.
That's a fixed location, unlike the engine which has a bit of leeway.
Basically, what I'm going to do is to hollow out the engine bay. The frame rails will come off, along with the inner fenders. That's not a big loss on the passenger's side, it was hammered very hard to clear that massive AC compressor years ago.
Once the bay is empty, I'll rebuild the frame rails with the right geometry to mount my Miata subframe. They're going to look quite different, but they'll attach up to the factory ones under the car if my tape measure is telling the truth.
Before any of this can start, however, I need to empty out the bay a bit more. So I'm pulling all the brake lines, clutch lines, wiring and miscellaneous parts. I've also reinstalled the radiator support to provide a bit more strength to the front of the car during surgery, and welded a couple of posts to it to prevent things from sagging.
entry 103 - tags: suspension, frame rails
December 10, 2008 - And here's what is going inside.
I walked into the shop at work and found this behemoth sitting on the floor. I have to say, it's very handy doing this swap at home while there are two LS3 Miatas being built at work as well as a completed LS1 Miata that's undergoing constant development. That's the drivetrain from the LS1 car, removed to get new heads and a cam.
It's a pretty close match to what I'm going to use. The subframe is the tubular version of a Miata subframe, with the same control arms and steering rack. It looks as if my engine positioning will be a bit further back than this one, which helps a bit for rack clearance, oil pan clearance and weight distribution.
It sure makes the transmission look huge!
entry 104 - tags: engine, subframe, transmission, fitment
December 10, 2008 - Turning my attention from the front of the car to the rear, this showed up today.
It's the rear axle from a 2000 Chevy S10 Blazer 4WD. The width is 59", 4" wider than the 2WD rear and a nice match to my front track. I've pulled the brakes to replace them with Miata parts, which is going to involve a bit of bracketry. Still, nothing too exotic. There's also going to be a lot of cutting of old suspension brackets and welding of new, of course.
I wasn't sure if this was going to be a limited slip or not. Experimentation would indicate not, and changing to the Camaro rear will mean setting up the pinion again. Oh well, it's another skill to learn.
entry 105 - tags: suspension, rear axle
December 10, 2008 - So, how do I locate the rear axle?
Hanging it off leaf springs just isn't an option for ride, handling and tuning ability. So I'll change over to coilovers and a multi-link setup. Lots of learning here, I've never had to deal with a big stick axle before.
This is a three-link setup as sold by Fast Cars, an MG conversion specialty shop. It would be easier to design and build than a four-link, especially with these photos. However, I'm not too excited about the concept of a panhard rod and the slight lateral movement of the axle it creates - and I'm really not a fan of that bent rod in the Fast Cars kit. This car won't spent a lot of time on the track, but you know it will happen!
More photos of this particular car can be found on BritishV8.org - it's a very thorough conversion and you get a really good look at the suspension design and brackets.
entry 106 - tags: suspension, design, 3-link, rear axle
December 10, 2008 - The other option for the rear is a four-link setup.
It's a little more elegant from an engineering standpoint - the axle is nicely constrained. But it's more of a challenge to design well, as there's potential for binding. I have to admit I'm not completely sure how to design that, or if it's really a risk. I've been running the kinematics of both designs in my head all day, trying to figure it all out.
The picture is of a commercially available kit from Classic Conversions, and it's actually designed to bolt into the chassis. Pretty nice. According to a writeup (with more pictures) on BritishV8.org, it's designed to have a bit of roll oversteer which is something I'd prefer to avoid. Still, it's a good option - although with a price of over $1000, it's more likely that I'll use it as a proof-of-concept.
entry 107 - tags: suspension, rear axle, 4-link
December 15, 2008 - Not much actual work on the car, but lots of planning.
I'm going to go with a three-link rear after talking with a number of road racers and other folks on the Grassroots Motorsports forum. The lateral motion of a long Panhard bar isn't a big deal at all it seems, and it's free of bind and easy to fabricate. So there's that settled. I just have to do it!
I'm also starting to plan the brake system. Very little of it will be MG by the time I'm done. In fact, it's possible it will all be custom. I'll have to wait until the motor position is determined before I can finalize this but it's fun to build it in my mind. Brakes are important to me, and I like putting together good systems.
This is actually a very entertaining part of the build. I have all of the major components so I can start legitimately planning and figuring out how to do things. On top of that is the anticipation of the first big steps coming up - I'm looking forward to that first chop of the frame rail with anticipation and a little frisson of nerves. This is the stage where the whole car comes together in concept, making it a complete machine instead of just a collection of bits that are a reaction to unforseen problems.
I love this part.
entry 108 - tags: suspension, brakes, rear axle
December 31, 2008 - It's been a long break over the holidays, but I wasn't able to get much accomplished due to visitors.
Still, I snuck away for a few moments here and there. At the moment, I'm still trying to figure exactly the best way to mount the suspension. First I need to make sure I have the centerline of the car marked. Here, I'm taking the center of the stock crossmember mounting points. I dropped a plumb line down from that X and marked it on the floor. After doing that with a few more locations, I'll have a good record and will be able to chop out the original frame rails.
entry 109 - tags: suspension