Track driven SR’s abuse their bearings if the oil level is allowed to drop one bit below the full mark on the dipstick, it is common to see the oil pressure fluctuate in hard corners with a car modified with good suspension and sticky R-compound tires. This makes it very temping for an SR owner to slightly overfill the crankcase to reduce the chances of this happening. This is also bad. A crankcase that is even slightly overfilled helps create a maelstrom of windage around the spinning crankshaft that both saps power and overheats the oil enough to torture the bearings. If you can imagine riding a bike underwater, this is what your crank experiences. This is the main reason why track driven SR’s run such high sump temps. When experimenting on the dyno, overfilling the crankcase by a measly ½ quart caused a drop of 6 whp on an SR20. Having piston coolers that shower the crank with hot oil dropping from the pistons simply compounds the problem.
|The Ishiwata-Johnson crank scraper uses a teflon blade that can be adjusted to it contacts the crank for maximum effectiveness|
To help reduce the engine’s sensitivity to oil level, gain power and to reduce sump temperatures we installed a crank scraper and windage tray from Ken Johnson at Ishiwata-Johnson Crank Scrapers. The crank scraper is a sheet metal part that is cut to closely follow the contours of the crankshaft. It bolts to the main girdle. The crank scrapers job is to strip oil off of the rotating crank assembly so it can be retuned to the pan instead of flying around in a dense cloud getting hotter and more aerated. We opted for the full race scraper which includes a Teflon insert which can be adjusted until it is actually in light contact with the crank to do the best job of stripping the oil cloud as possible.
|The Ishiwata-Johnson windage tray also helps strip the oil from the rotating crank|
We also opted to run the full race windage tray. A windage tray is a louvered plate that is designed to capture oil from the windage cloud that surrounds the rotating crank and return it to the sump before it gets hot and frothy. The full race windage tray goes completely across the engines bottom end to strip as much windage from the crank as possible. However the full race windage tray requires some cutting and welding of the oil pan for clearance. Ishiwata-Johnson also makes a ¾ length street version of the windage tray that does not require pan modification.
|Here is the teflon scraper in place. Note how it contacts the crank to positively remove oil from it|
The windage tray and crank scraper work together to greatly reduce the amount of windage in the crankcase. Eliminating the turbulence and oil mist generally gives a power increase of 5-6 whp and reduces the sump temperatures by 10-15 degrees. Oil with less entrapped air also does a much better job of lubricating the engines innards. With less oil getting thrown around, the engines oil consumption goes down as well as the rings are not overcome by the volume of oil thrown on the cylinder walls. Although this part is not absolutely necessary for a low buck build, it is very reasonably priced and gives a free gain in power, something that is hard to overlook in an all motor build.
|The Ishiwata-Johnson crank scraper and windage tray in place. We opted for the full length assembly. Although this works much better, The oil pan must be modified for clearance. A half length windage tray is also made for an unmodified oil pan.|
|To run the full length windage tray, we had to modify the oil pan for clearance by cutting holes in it and capping them for bolt clearance as well as cutting out and capping a hump in the rear of the pan. Its a hassle but we feel its worth it|
With our engines basic bottom end details being solidly taken care of and plenty of attention to minor details, we have still managed not to spend too much money. In our next edition of Project Low Buck we will start to massage our cylinder head and design some really cool headers for our budget build.
Castillo’s Crankshafts Specialty