Tuesday, September 30th, 2014

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Admittedly an aluminum driveshaft isn’t at the top of the list of budget performance upgrades. The biggest bang-for-the-buck improvement is just more track time, period. Then there’s the basics of good tires, good set-up, and good maintenance. Once the basics are covered you can start working on upgraded suspension, brakes, gearbox and engine, and of course weight loss (both car and driver). But once all the low-hanging fruit is gone, you should start doing your cost vs performance calculations wisely when picking the next upgrade. Basic physics shows the greatest advantage in weight reduction comes from unsprung mass and from rotating mass, ie wheels and tires, brake components, crankshafts, and yes, driveshafts.

After a recent gearbox swap in the 710, I was needing a new driveshaft, so I figured it was an appropriate time to do an aluminum driveshaft upgrade. At the same time I increased the diameter of the driveshaft from 2.5″ to 3″. I found some engineering tables that show the dramatic strength increase realized by just small increases in a tube’s diameter, therefore helping reduce driveshaft whip at high speeds. And even with the increase in tube diameter, I dropped the weight substantially by switching from steel to aluminum, from 15 lbs to 11 lbs. Yes, it cost almost more at $450, but since I was needing to have one made anyways, I think it’s an upgrade worth the money. If you’ve really got some extra bucks to throw into the project, a carbon fiber driveshaft will increase strength and reduce weight even further. The guys at South Bay Driveline in San Jose, CA did a great job as usual, and they don’t make me feel stupid with all my dumb questions ;-)

Last week I raced the Crossle at Buttonwillow Raceway and the afternoon temps were over 100 degrees. Well I found out what those cool looking air ducts behind the radiators are for on other cars I’ve seen, to divert the radiator exhaust air away from the pedal box. My feet were on fire, I actually thought my left shoe was melting! So my crew mate Art whipped up a cardboard air dam to get me through the weekend, and it worked great. Who needs swoopy looking carbon fiber anyways ;-)

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Spent a little time in the garage today cleaning up the old 710 grill. Gave it a power wash, rubbed it down with a little fine sandpaper, then some acetone. Spray painted it with Krylon Fuzion plastic-adhering satin black, hand painted the perimeter with some metallic silver, cut and formed some 3/16″ stainless steel wire mesh for the headlight grills, and couldn’t resist installing a spare Datsun grill badge from the Wagon. Now it’s the best looking part of the car ;-)

Datsun 710 grill

The h165 axle on my Datsun 710 had 1/8″ toe-out and zero camber. It made the handling a bit twitchy and did not give ideal tire wear, so I took it to Paul Moore at The Moore Speed Co and had him fix it for me. After removal and measurement, he used the cut-and-weld method to alter the axle housing geometry to an ideal 1/16″ toe-in and 1/2 degree negative camber.

710 axle camber adjustment

 

710 axle toe adjustment

 

 

This a great old video from 1965, definitely worth the 15 minutes. It includes some race driving instruction around Willow Springs Raceway by Peter Brock, Ken Miles, and Dan Gurney.

 

This weekend I made my maiden visit to Portland Int’l Raceway for the 2014 HMSA Portland Historics, with Datsun being the featured marque. Over two dozen Datsun 240Zs, 510s, Roadsters, 710s, and even a GTR Skyline showed up to support the first ever major U.S. Historic event spotlighting the venerable Japanese manufacturer. Mr. John Morton of BRE fame was the event Grand Marshall, and he regaled us with great stories of how he got his start in racing during the HMSA-hosted Saturday night dinner and award ceremony.

The driver-friendly, 2.0 mile, 12 turn track has a dragstrip front straight, a curved back “straight”, and a fun complex of corners connecting the two ends. HMSA and the local SCCA track workers ran a nice, organized three-day event, featuring a practice, qualifying practice, two heat races, a warm-up, and Sunday flag race. Friday and Saturday saw record high temps testing car’s and driver’s cooling systems alike, while we raced in the rain on Sunday. Combined with a 12-hour tow each way, it made for a long, yet very enjoyable, weekend.

I battled some brake and axle seal issues with my recently purchased Datsun 710 race car on Friday and Saturday, but with the help of my pit crew and fellow Datsun racers, I had things in order for Sunday’s flag race. Thunderstorms and lightning filled the skies for race day, and while some groups raced in a drizzle, some raced in a deluge. Most racers stuck it out, but I was suprised by how many packed up and left in the rain. My B-Sedan/2.5 Trans-Am group got lucky with just light showers, but it still made for an exciting session on DOT cheater-slicks. I got to learn a new track, see some new cars, and make some new friends this weekend. We finished 6th in a group that started with 24 competitors, so I’ll call this Oregon adventure a complete success!

Eagle Mk 5 Datsuns at PIR Datsun pits HMSA award ceremony #73 pits S&H Pink Stamps v8 sportsracer Nissan GTR Skyline, RHD The un-Datsun Gulf Porsche 911 and pitbike

You see the coolest pit bikes at the races…

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