I’ve been collecting (aka buying, scrounging, trading) parts for the past 2 years so I could build a spare motor for the wagon. This one is another long-rod L20b, +2mm forged flattops with cutouts, prepped crank, big-valve A87, planning 12:1 CR. It’s gonna be really nice having a spare bullet in the chamber when I gotta pull out my current engine.
Hey Troy, thanks for the info. Hope to see you at one of the races in the very near future!
Hi Kevin, other than a good inspection and measurement for proper sized bearings, the only must-do mod for racing is balancing the rotating assembly (crank, rods, pistons), and if you can balance it with the flywheel and clutch as well, even better. The stock Datsun cranks are amazingly stout and well oiled. If price is not an issue and you’re spending time and money on all the other little things, then lightening and knife-edging the crank will get you that little extra. A good machinist can take about five pounds out of a 510 crank without much problem.
Hi Troy, you had mentioned your spare motor has a prepped crank. What do feel are necessary mods to the L20B crank for full out racing? I’m getting ready to take it in and was wondering if lightening, or cross-drilling, polishing, etc are must-do mods.
Thanks!
Kevin.
Yep, I used a set of prepped 6″ Datsun rods, and had a set of custom forged 87mm pistons made with a shortened pin-to-top distance to give me a flat top with the deck. The numbers are buried somewhere in my garage, but probably available if you hunt around on the web. I just did the math based on crank throw, rod length, deck height, and then ordered them. With a small chamber head, it ends up about 12:1 cr.
Did you end up going with a 6″ rod and moving the pin upwards in the piston? I”m looking at doing a long rod setup and trying to get the right piston specs.