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My Lexus SC400 Project

Old 06-10-2012, 03:26 PM
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My Lexus SC400 Project

I bought my 99 Lexus SC400, with the plan of making some significant suspension modifications to improve the handling and installing an exhaust system and Unichip computer to tune the engine performance. The car has 103k miles on it, so it was time tor a timing belt and water pump, as well. My budget is limited, so I focused on chassis tuning and getting the most out of the stock engine.

When I first drove the car, I was hoping I would like it when I was finished. The handling was mediocre, at best. The body roll was excessive, with about 3 degrees of roll before the sway bars even started working. The all-aluminum 4.0 litre VVT-i V8 definitely had potential and made all the right noises. The brakes were woefully inadequate. The chassis is nearly identical to the Toyota Supra MkIV, so I knew it had potential.

I don't have the photos I took of the car when I bought it, but here it is after doing some work on it:


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Old 06-10-2012, 03:39 PM
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The headers are much easier to install with the heads off and since I would be installing a timing belt, I was already about 60% of the way to having the heads off and since I was going to have the heads off, I may as well do some porting and new valve seats, because then the heads would work way better with the headers and exhaust system. So the head work was planned and placed on the back burner, while I got started on the suspension.

So I put the car on jack stands and got started taking the suspension apart at the beginning of December. It was dirty, nasty, awful work. I always told myself that I was going to buy a used car from the desert southwest, like Phoenix, AZ. That was a good plan. But the car I bought was from the wet, icy, salty, nasty northeast. That was a bad plan. The body and main chassis are in great condition, but everything bolted to it was corroded and caked in baked on road grime ~1/8” thick.

The suspension pivot bolts, which are on eccentrics for adjusting camber at all 4 wheels were corroded to the tubes that they pass through, which are mounted in rubber bushings. The front, lower control arms could not be removed. The through-tubes are hardened steel. I couldn’t get to them with a cutoff disc or anything else I tried. I bought some diamond-coated Sawzall blades. I was able to remove the front bolts for the control arms, but had to drop the crossmember and control arms out together, because the rear bolts were fossilized. Diamond-coated Sawzall blades are not recommended. I started trying to cut the control arms out and after 15 minutes of reciprocation, nothing happened. That’s when I went shopping for new control arms and a front-aft crossmember. The control arms came with new lower ball-joints – in fact you can’t replace ball joints without replacing the control arms. I found a used crossmember and bought it for $150 on ebay. I got the part and realized that early SC400s don’t have a diagonal brace for the lower control arm that the late model ones have. I then had 2 useless front-aft crossmembers. I contacted the seller and he took the wrong part back and sent me the right one at no charge!

The rear suspension almost came apart, after twisting the 3/8 drive stubs off of two -3/8 socket adapters and splitting the sides on a 19mm socket. One rear lower control arm was similarly melded with its mating part and impossible to get to. So that’s when I decided to drop the entire rear subframe out of the car. Rear subframes are quite a bit more expensive than front-aft crossmembers, so I found another use for diamond-coated Sawzall blades.

But in order to get the contol arm out of the way of the pivot tube, I had to heat up the control arm until the rubber bushing started to smolder and flame, thereby releasing its grip on the control arm. Good thing I was in the shop at work, with a big exhaust fan. Then I had to cut through some more rubber to get to an aluminum tube. I didn’t need diamond blades for that, but I had to get it busted up and removed so I could get to the 7/8 diameter hardened tube and pivot bolts. Once I got another layer of rubber removed I could start in with the sawzall. One hour later, I was through the bolt on one side of the control arm – halfway there. By the end of the night, I was through the other side.

The hubs and brakes were caked in scaly rust and horrible funk. After I got the rear hubs out, I noticed that one of them was missing a bearing seal! I decided to take the hubs to the local Automotive machine shop and have all of the bearings, races and seals replaced, because it was becoming apparent that somebody had been working on the car. They got the hub with the missing seal apart and the certified professional mechanic had tried to get the inner bearing race off with a torch and had burned a hole almost through the hollow stub-axle. He then fixed it up with a file, so the new race would go on. A new rear stub-shafts was $180.

While he had the hubs apart, I had him bead-blast the housings. I treated them with a rust neutralizer, an etching primer and Krylon Rust-Tough paint. Since I had a bunch of other nasty, rusty parts laying around, I bead-blasted the other suspension components and had the rear subframe sandblasted to bare metal and gave them all the same treatment. The parts came out beautiful! And I was finally starting to look toward the finishing line.






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Old 06-10-2012, 03:48 PM
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nice looking work
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Old 06-10-2012, 03:51 PM
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While I had all of the rear suspension out, it was easy to drop the rear differential out. I found a used Torsen T2R limited slip rear differential for a Toyota Supra that is a direct fit. It wasn’t too difficult to disassemble the rear differential, remove the ring gear and install it on the Torsen unit, clean everything up and put it back together. My first finished assembly in what has turned out to be a major restoration project.

Stock differential:



Torsen T2R installed:



Next I started reassembly of the rear suspension. I installed the control arms, including two new rear lower arms to the rear subframe. I then slid the assembly under the car and lifted it onto place with a 2X4 and floor jack. Once I had it bolted in place I reinstalled the differential.




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Old 06-10-2012, 03:59 PM
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The front suspension was easy. I bolted up the new used crossmember and installed the control arms. Lots of nice, light aluminum parts in the suspension and chassis. Note the aluminum main crossmember/engine support.



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Old 06-10-2012, 04:04 PM
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One of the things I did to help with organization and reassembly was to clean every fastener with a wire wheel and sort them by size, type and strength and put them into trays. It makes it really easy to pick the correct fasteners and clean threads make it so everything goes together with a twist of the fingers using anti-seize grease on the threads.

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Old 06-10-2012, 04:15 PM
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Since I had the suspension back under control, I decided it was time to start in the engine compartment. It was fairly clean, but all of the aluminum parts were covered in a white, scaly corrosion and all of the steel brackets and fasteners were rusted and nasty. The engine is very similar to the Tundra engine, so I know the drill getting the timing belt and water pump off. After a couple of mornings, lunch breaks and evenings, I had the heads off. The alternator was so ugly, I couldn’t think of bolting it back on, so I took it completely apart, inspected everything, cleaned the housing, beadblasted and painted the pulley and put it all back together. The power steering pump was leaking and completely caked in oil and dirt. The power steering hoses and mounting hardware looked like something from you'd see at a harbor on the north coast. I took the power steering system apart to the component level and cleaned, for more wire-wheeling, beadblasting, paint and reassembly. I started to take the power steering pump apart, to replace the seals, but decided to buy a rebuilt pump.



The chassis was built for the inline 6 engine used in the Toyota Supra and Lexus SC300. The V8 sits almost entirely behind the shock towers, making it a front-mid engine mount, like the Honda S2000 and a few other high-performance road cars. The aluminum V8 looks sweet, resting on a big aluminum crossmember.



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Old 06-10-2012, 04:34 PM
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I took the heads completely apart, cleaned everything and went to work on the porting – hours and hours and hours and some more hours after that later, I had the porting done – all 32 of them. I didn’t even do anything very fancy. The exhaust ports had a very abrupt, poorly finished transition from the valve seat into the floor of the port, so I put a smooth radius in. I also opened up the throat area around the valve guides to open them up and narrowed the dividing septum. Other than that is was just general cleanup and blending of all the radii. It takes a while, when working on ports to be able to really see the 3-D shape. I’m pretty happy with how they came out. I’m really happy with how they run.

Stock ports:



Reworked ports:


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Old 06-10-2012, 06:03 PM
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After porting, I cut new valve seats. They came out really good. The seats were all concentric with the valve guides, the placement of the seat was out near the edge of the valve face to maximize the flow area and they all look nearly identical – all 16 intakes and 16 exhausts. The heads were now super clean and ready for assembly.




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Old 06-10-2012, 06:15 PM
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Assembled the heads:






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Old 06-10-2012, 06:21 PM
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Installed the headers:




Stock header, for comparison. Look how the exhaust gas is shot straight at the back side of the manifold. It will inevitably flow in all directions, when you do that. Not good:

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Old 06-10-2012, 06:27 PM
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Prep’d the block:




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Old 06-10-2012, 06:30 PM
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Installed the heads:

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Old 06-10-2012, 06:36 PM
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Installed the cams, measured and recorded the valve clearances, removed the cams, ordered and installed the valve shims to set the valve clearances and reinstalled the cams:


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Old 06-10-2012, 06:44 PM
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Installed the timing belt and accessories (alternator, PS pump, AC compressor, etc.):



Installed the serpentine belt and found all of the wiring terminations:



Installed the lower intake manifold, fuel injectors, spark plugs, coils, airbox. I made some modifications to the upper manifold. It is ready to install, along with the radiator, fan and throttle body. The engine compartment is almost complete:


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Old 06-10-2012, 06:52 PM
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Set up strings, set suspension to the proper ride height and did a preliminary alignment with no suspension load. I had no reference for where the suspension was previously, so I set the camber angles to -1 degree and the toe-in to 20 minutes (about 0.1” in 18”). Once the car was drivable, I took the car in for an alignment, to my specs. It was easier to get started with the car on blocks, because I could measure and adjust without having to lift and lower the car.



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Old 06-10-2012, 07:01 PM
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The next phase is the brakes. They were all rusted and working poorly. I’m replacing the entire brake system with bigger, better brakes from a ’98 Toyota Supra Twin Turbo. I removed and cleaned the master cylinder and reservoir and painted the vacuum-assist housing:



There really is no comparison between the stock brakes and the TT Supra brakes. They are in an entirely different class:



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Old 06-10-2012, 07:15 PM
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Sweet ride!!!
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Old 06-10-2012, 07:32 PM
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I put a lot of thought and study into selection of shocks and springs. I see a lot of cars that are excessively lowered and the suspension is like a go kart. i wanted a firm, but compliant ride and exceptional handling. I looked around a lot, read a lot of reviews of the different coilover shocks available.

Then I found a site called Autocross To Win. It is put together by a guy who is very serious about suspension tuning. His site is a wealth of useful information. He dynos every shock before he uses it, so he knows what works and what doesn't (which is most of the aftermarket coilover shocks). The best, most consistent shocks he has found are Bilsteins. Their road shocks have the same valve assemblies as their racing shocks and are every bit as tunable. They make a coilover sleeve for them, so you can use standard 2.5" ID racing springs.

The site has a dynamics calculator. You measure the shock actuation ratio and get the corner weights for the car, then establish a target natural frequency for the suspension (the natural frequency is the frequency that the car would bounce at, if no damper was installed). For example, a full-on track, or autocross car will have a suspension natural frequency between 2.0 and 2.5 Hz (cycles/second). A comfortable touring car would be around 1.0-1.2 Hz. A boatride suspension is below 1 Hz. I knew I didn't want a race suspension, so I set my target natural frequencies at 1.5 Hz in the front and 1.7 Hz in the rear. With this information, I could establish the spring rates, front and rear. There is also a calculator for the low-speed (0-3 in/sec) and high-speed damping rates, based on the same natural frequencies. I bought a new set of Bilsteins for a Toyota Supra and sent them to North Carolina to a guy that builds racing shocks. I gave him my target damping rates and had him install Schrader valves so that he could recharge the shock with nitrogen. He also cut snap ring grooves, to support the coilover sleeves. I also ordered a set of Toyota Supra racing swaybars from Titan Motorsports. What I ended up with was an engineered suspension system for my car:




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Old 06-10-2012, 07:57 PM
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I had a cat-back exhaust system fabricated, before I put the car on stands. It had these horrible gold-colored exhaust tips and I refused to drive with them for even a day. There are not a lot of choices in Minden/Gardnerville NV for getting exhaust work done. the guy I took it to did an absolutely horrible job. But for the most part the pipes are usable. I have since found the old guy that does custom exhaust work out of his home shop, with a mandrel bender and the whole works. I'm going to have him fix the ridiculous muffler mounting and try to salvage the rest. I used a crossover pipe from Summit Racing and installed Magnaflow spun cats, after the headers were installed, to keep the pipes tucked up tight, since the headers are a bit longer than the stock manifolds.



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Old 06-10-2012, 08:10 PM
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The final step in this part of the project was to install a Lambda (wideband O2) sensor and the Unichip piggyback EFI controller. I am in uncharted territory here, since it has very rarely been done on these engines. I had to solder the wiring connections in to the main wiring harness. Unichip has a "tuner" package available, with software that does the mapping. You can map it while you drive, or better yet, put it on a dyno and map it with the Unichip software. I contacted a local race team with a dyno and got permission to rent some dyno time from them. I have had a few bugs with the computer - apparently Toyota ECUs are very particular about grounds and loads and it has been difficult to get it all working. I think I'm close, but have been unable to work on it for the last couple of weeks. I can install a dummy block that takes the Unichip computer out of the system and the cars runs pretty well with the stock map.

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Old 06-10-2012, 08:18 PM
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Nice car man! Love those supra brakes. Anything that has ties back to the Supra is ok by me. Love it man. Keep up the good work.
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Old 06-11-2012, 06:08 AM
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Nice project! I've always like the SC series, and I've been a huge fan of the 1UZ motor. There is a lot you can do with one, i've seen them built twin turbo put out up towards 1000HP.

If that was my project something very high on the list would be to swap in a 5 speed. There are transmission adapter plates to use either the W58 or R154 5 speed transmissions.

Keep up the good work.
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Old 06-11-2012, 06:18 AM
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Ah yeh. Love these. THAT'S how you build a v8. Hear that GM? Now it just needs Hbeams, pistons, twin turbos and an EMS. Oh, and probably a bigger rear view mirror so you can see WAY behind you and find out who's in second.
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Old 06-11-2012, 06:47 AM
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Originally Posted by 98VTRrider View Post
Nice project! I've always like the SC series, and I've been a huge fan of the 1UZ motor. There is a lot you can do with one, i've seen them built twin turbo put out up towards 1000HP.

If that was my project something very high on the list would be to swap in a 5 speed. There are transmission adapter plates to use either the W58 or R154 5 speed transmissions.

Keep up the good work.
Yes, a 5 spd manual is on the short list. But the 5 spd automatic does a good job. You put it in 3rd in the tight twisties, it shifts to 2nd to pull off the corners and it's an absolute beast. More driving impressions to follow.

Last edited by RCVTR; 06-11-2012 at 06:52 AM.
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Old 06-12-2012, 05:34 PM
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The photos and descriptions show most of the high points of the project. What they don't show are the hours spent between the photos. The stupid @#%(^ fasteners that I couldn't see, but knew the $&% hole was there somewhere. I started at the beginning of September and worked every hour that I could find for 5 months. The last several weeks, I was so burnt out and tired that I didn't think I could get it done. Winters are long and cold around here, but once springtime hits, we are super busy, so I knew I needed to get it done, or I would lose momentum and it would sit there. So I just kept forging ahead. If I looked at all the **** that I had left to do, it was completely overwhelming, so for every little window of time, even if it was just 1/2 hour, I would focus on one minute detail and cross it off the list. It was definitely one of the biggest projects I've taken on, besides remodeling a house - it was way more fun than that. I finally wrapped it up - at least to the point where I could drive it - in mid April.
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Old 06-12-2012, 06:07 PM
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My son is attending college in San Luis Obispo, CA. One of my big, driving goals was to take my car to San Luis for a visit. That gave me the momentum to finish it.

I got the car finished and took it for a test drive up Kingsbury Grade - my daily commute. The first thing I noticed was that the car just wanted to break the rear end loose and slide through the corners. It was fun, but I wanted it to be more hooked up. I had bought a set of TT Supra wheels that came with a set of Falken Ziex tires with "70% tread remaining" on ebay. The joke was on me on that one. The rears were down to the wear bars. I didn't want to take them on a 6 hour road trip on one of the best roads in California, so I bought a set of Dunlop Z1 Star Spec tires. I thought it was better to have too much tire, than just barely not enough. If there is a better tire for that car, I don't need it!

I left work on a Friday afternoon, down Hwy 88 from work. That's a pretty good road, but a fair amount of traffic, so I got to do a bit of testing, but I knew the best was down the road a few hours. I was headed for the southern section of Hwy 49, site of the best motorcycle riding I've done on public roads. I had to be patient and enjoy the scenery until I got south of Sonora and turned of on South 49. From there, I saw 4 cars in 50 miles, on some of the best, most technical highway, with perfect pavement that you can imagine.

I knew the road well, because I had ridden it on my VTR several times. The lanes are narrow, there's a 400' drop on the right, with no guardrail and a rock wall on the left, so there is no room for error, especially considering the tight corners, with no visibility. There was every combination of compression corner entries, unweighted corner entry, short chutes between corners - the perfect environment for a torque monster, with great suspension.

I drove the car as hard as I could, considering the environment, romping the throttle, stomping the brakes and just attacking the corner entries. The harder I drove it, the more it wanted. I couldn't get the thing upset in any way. I felt the whole time like the car was just begging for more. It was beyond the wildest expectations I had for the car. The balance is simply unbelievable! I'm going to enjoy this car, for a long time.

Needless to say, I won't be driving down I-5 any more...
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Old 03-21-2013, 02:31 PM
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I have a nicely modded '99 SC400 myself. I've actually been looking into doing a UniChip tune on it as well, but am new to ECU tuning.
I'll send you a PM, maybe you can give me a few tips?
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