One night about a year ago, I went down a rabbit hole, trying to figure out if there was a cheap and light flywheel that will bolt to a 5S crank, but have the surface area of a 3SGTE flywheel. This isn’t terribly common because the 5S uses a 10mm thread on the crank, but the bolts have a 12mm shoulder, the 3S crank uses a 12mm thread on the crank, the flywheel bolts are just straight 12mm. The hole centers for the flywheel-to-crank are like 1-2mm closer to the center of the crank. The aftermarket solution to this is to make those flywheel holes oblong, Fidanza does this, and others (maybe ACT Prolite as well). This is common from the use of 5S blocks and cranks for 3s strokers. After much squinting at the XTD 12lb 3S flywheel photos, it seemed like they may have oblonged holes too, and it was $115 on eBay. So I bought one, and didn’t even know for sure if it would bolt up for about a year. First impressions seem good, except for no SFI certification. I guess time will tell if this thing Beyblades itself through the firewall and into my legs. The other day, I bolted it up, and it certainly looks like it will work fine.
The reason we want a 3S sized disc and flywheel? Well, it will work if we ever swap to a E153, E350/E351. It will also will give 18% more surface area for friction.
So just stick a 3S disc in there, right? No. The S51/S54 uses a 20 spline where the E153/E350/E351 use a 21 spine. It turns out that this is a solved problem: ACT sells a S51/S54 splined disc for a 3S swap, the part number is 3000614.
Lastly, I’ll need a 3S pressure plate. Because this is lowish power, I just bought a stock MR2 Exedy clutch kit# 16062, because nobody seems to sell the pressure plate by itself. They don’t even list the pressure plate part number by itself. For reference the stock Exedy 3S pressure plate part# is TYC572, but you’ll notice that basically nobody sells this by itself, and if they do, it’s $100 (or sometimes exceeding the price of the kit), where the kit itself is $150.
So the combo I’m running is a XTD All-Trac/MR2 12lb flywheel, ACT 3000614 clutch disc, and Exedy TYC572. This should have no trouble holding 250whp, maybe upwards of 300, should rev quicker but be about as grippy as a stock MR2. All in this setup is about $400, which is about the price of a Fidanza flywheel alone.
I’ve included a bunch of photos for reference, including comparisons of a stock flywheel. I also designed and 3d printed a low-quality alignment tool, since I don’t have a 5S one handy anymore.
