Thrust bearing and crank thrust face failures often occur from running too heavily sprung of a clutch plate. These types of failures are pretty common in the 4G63 world but not very common with the SR20DET. The other cause of this type of failure is insufficient thrust bearing clearance. Taking into account that we’ve run the same JWT clutch for hundreds of thousands of miles with no problems and that both Nick Hunter and I had verified the thrust bearing clearance upon assembly, we were left scratching our heads.
That is until we noticed something peculiar. Normally SR20DET crankshafts have an undercut radius between the journal and the thrust face. This one did not, which meant it had been welded and repaired at one point. Looking at the thrust face under magnification, it became obvious that the welding on the thrust face was porous, which most likely caused it to start breaking down and in turn, the bearing to fail. Keep in mind that the welding and offset grinding to de-stroke our crankshaft only involved the rod journals, not the mains.
Fortunately, 5523 Motorsports had built a spare bottom end last season, which we already had sealed by the SCTA a few years back. The bottom end featured the same JE Pistons, K1 Technology connecting rods, and a SR16VE crankshaft sourced from Greg Vogel at G Spec Performance that was modified by Marine Crankshaft to reduce the stroke to 2.500″. Murphy’s Law wouldn’t stop there though.
In addition to driving fast, I’ve also picked up a new hobby in the last few years, downhill mountain biking. What I love about downhill mountain biking is the adrenaline rush you get without having to pay hundreds of dollars for race gas and tens of thousands of dollars to build a racecar. The exercise and time with nature is nice too; however, I’m clearly in it for the thrill.
I also downhill mountain bike to stay sharp and it turns out a lot of pro athletes do too. There’s something about flying down a mountain dodging trees, shredding berms, dropping off the face of boulders, and hitting big table tops that parallels land speed racing. I think it’s about putting yourself in those “oh shit” moments and getting you used to maintaining your composure during them. It also keeps me comfortable with that sensation of speed that would easily make other people wet themselves.
Having seen some of my spectacular GoPro crash footage on Instagram, both John Kuchta and Nick Hunter had warned me to “lay off of the downhill mountain biking crap” before I hurt myself. Half heartedly heeding their message, I told myself that I’d stop one month before Speed Week. Almost exactly a month before Speed Week though, I’d dislocate and fracture my elbow jumping a new feature at Snow Summit’s bike park. Stupid, stupid, stupid!