The pursuit of more power can only be achieved when supporting mods are firstly established. That’s why I decided to move forward with a clutch replacement. The stock clutches on RX-7’s are a weak-link as they are only good until around 300 HP before slipping. Picking which replacement clutch to go with wasn’t easy, I ultimately narrowed my choices down to an ACT Heavy Duty/Xtreme Duty or an Exedy Twin Plate.

Typically, I’m all for overkill, but you have to choose more carefully when it comes to clutches. I heavily emphasized NOT sacrificing drivability. The ACT Heavy Duty pressure plate with Street Disc clutch (HDSS) stood out as being the most reasonable choice. It supports up to 400 ft/lbs of torque which should be sufficient. The actual clutch is a full-face unit, and not a puck style so this will aid both drivability and longevity. I decided against going with the Xtreme pressure plate because I think it would make the clutch pedal too stiff and it may be too taxing on the RX-7’s clutch hydraulics in the long-run.

I also wanted to change out the flywheel and went with the 9.5 lbs ACT Prolite.

To ensure that this clutch job is as thorough as possible, I called up Ray @ Malloy Mazda and ordered all possible oil seals, an automatic counterweight (required to install an aftermarket flywheel), and a new clutch fork. I ended up buying one too many seals, only the rear main seal and transmission tail-shaft seal were replaced. Like the seals, the clutch fork was primarily preventative maintenance and also complimented the stiffer pressure plate. I read that they fatigue and crack, especially the earlier ones from ’93 cars. Mazda later strengthened them with I guess better casting. Lastly, I found a steel braided clutch line that I bought almost 4 years ago and never had a chance to use until now.

I like to work on this car myself whenever possible because I want the control; however, sometimes you just need to enlist the help of a shop. I’m sensible enough to realize that wrangling off a transmission on my garage floor is beyond my scope. Instead, I brought the car over to the knowledgable folks at P R Motorsports, who specialize in Mazdas and, specifically, have done work on RX-7’s.

When I dropped the car off, I didn’t overextend my stay and left for work relatively soon… still, I think the owner, Laura, was keen enough to sense my paranoia and criticality. Throughout the day, she sent me numerous updates and pictures. I’ve never had a shop do that for me before, which was very cool and I definitely appreciated the thoughtfulness.

Here are a couple pictures from the shop.

I was able to pick up the car the same day. Driving review: the engagement point is quite close to stock and the pedal is slightly stiffer. I’m happy with the pedal feel, I prefer it over stock. I don’t like stepping on rocks, while light pedals don’t provide enough feedback. I was most interested in gauging the difference from the flywheel. Maybe my driving history with the car is not long enough yet, but the change in feel was more incremental than revolutionary. I didn’t encounter any difficulty with starting off, which I thought I would. The revs do climb and drop faster, although not significantly. I honestly think a lightweight flywheel should have been a factory standard.

3 thoughts on “ACT HDSS Clutch & Prolite Flywheel

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