Trying to get all the engine components to work harmoniously and live a long life in a single-turbo Supra can sometimes not be so simple. Shortly after the boost was incrementally turned up our stock-cam car was seeing over 520 whp on 93-octane equivalent fuel on evosport's Dynojet. Our goal from that point was to get a decent baseline with the stock cams, install a set of HKS 272 cams, and retest.
Unfortunately things didn't work out as planned. After evosport's Gary Karamikian installed the HKS cams we went out for a drive to get the timing and air-fuel ratios right. Shortly into the drive-and-tune session the bracket for the timing belt tensioning pulley cracked. It happened over the course of the first couple of boosted pulls over 20 psi. As torque increases, so does the tension on the timing belt and, thus, the force on the tensioner and bracket.
Since evosport didn't have a lift available right away the car was towed a local Turbo-friendly shop, Under Pressure Fabrication and Distribution, where we found that the cracked pulley also chipped a piece off the housing of our new oil pump. To our disgust, replacing the housing requires us to drop the oil pan and subframe to replace it. We ordered a new factory oil pump gear and housing from Champion Toyota in Houston, Texas.
Fortunately the timing belt didn't slip off when the tensioner broke, but it was time to look for a fix regardless. To our rescue came the crew at Sound Performance. After seeing this happen to numerous Supras, Sound Performance recently introduced a billet tensioning bracket to replace the cast O.E. unit. We wish it would have been available sooner-and now you know as well. This billet piece of 4130 chrome-moly is sure to outlast the factory unit.
As long as we were back under the hood we hunted down other parts we felt could possibly fail in the near future. The stock crank damper was one. Apparently many Supra owners have been having problems with these coming apart. To avoid ever going through this we ordered a crank damper from Boost Logic. This machined damper has a steel and press-fit hub to prevent cracking and keyway gouging. The best part is that it weighs only 5.5 pounds (compared to the 7.5-pound stocker), a reduction of over 25 percent in rotating mass.
Since the accessory belts would be coming off anyway it was a good time to take advantage of Boost Logic's accessory lightweight aluminum pulleys as well. We got pulleys for the power steering pump, alternator and water pump.
We didn't have a scale with a higher than 0.5-pound resolution on hand but the stock power steering pump pulley registered 1.0 pound and the new BL aluminum replacement didn't even register. BL pulleys are SFI 18.1 approved and use the factory accessory belt. Although lighter, these pulleys don't under drive the accessories. The engine, however, will love the decrease in weight of the rotating assembly.
A camshaft, crank damper and belt tensioner bracket installation requires the removal of the timing belt and re-timing of the cams to the crankshaft. You'll save a lot of time and money if you do them all at once. It's not a bad idea to go ahead and install a new timing belt while everything is easy to get at.
You may have noticed in the previous installment a few new components that were not mentioned at the time. First off, our previously featured engine rebuild included upgrades to the cooling system in the form of a PWR radiator. The PWR unit is nearly an O.E. replacement-all we had to do was trim a bit off the plastic battery tray to make room for the larger end tanks.
The additional 1.25 quarts of cooling capacity will ensure better management in the temperatures cooler during high-performance driving. As with a turbocharged BMW M3 project I managed for our sister magazine, european car, it should help keep the oil temp down significantly too. With the M3 the oil temp dropped over 35 degrees Fahrenheit after the addition of a high-capacity radiator. The oil temp never exceed 200 degrees on the track!