rwatson5651

iTrader: (5)

Long story I know, but here goes:

I have had three engines in my S/A. The first was the stock 12 A, the next was a Hayes Rotary Street port four port 13b (back in 94 or 95), and the current version is a larger streetport four port 13B That I built myself. Both 13 Bs equipped with a RB light steel flywheel.

When I first got the Hayes rotary engine I noticed that it was not nearly as smooth as the original 12A. It was not so bad that I thought there was a problem, and Hayes assured me the engine internals all matched so that dynamic balancing was not necessary, so I lived with it for twelve years till it dropped an apex seal.

Anyway, when I built the last engine I wanted to make sure it was as well balanced as possible, so I sent the internals to Mazdatrix for dynamic balancing, put it all together and it felt only marginally better than the Hayes Rotary version. I was a little disappointed, but I figured it may be the nature of the 13 B rather than the 12A, (especially a streetported version with a light flywheel) so I was resigned to it as be just the way it was.

Well the centerforce clutch I put in the latest engine did not hold up and started slipping after only 3000 miles so I wanted to upgrade to the Exedy Stage I that everyone seems to go to, problem was my flywheel was the 215 mm variety that they no longer make, so I thought I would have to buy a new 225 mm flywheel. Then I found out the only difference between the two were some reliefs machined into the face of the pressure plate, so rather than buy one I took mine to my machinist who did the needed work. He has a balancing machine so I asked him to rebalance the flywheel to make sure it was right, and since I had the new pressure plate I had him balance them assembled, wondering if it would improve the smoothness of my engine.

All I can say is WOW. It made a hugh difference.

Before the engine didn't mind revving to redline, now it begs to go there, feels like a whole different engine.

I was so impressed that I wanted to share my experience, sorry for all the verbiage, but

has anyone else had experience with flywheel/pressure plate balance?

The only downer is I have since learned I may have been able to find a 215 high performance clutch and avoided all this, but in a way I'm glad I didn't cause I learned of the benafits of balancing the flywheel and pressure plate together.

t_g_farrell

iTrader: (1)

I know when I swapped in the 82 stock flywheel on my 80 12A, there is a slight vibration. I had
the flywheel resurfaced and it is an 82 flywheel with an 80 rotating assembly so I assume there
is some minor balance issues with the setup. Back in the day this was an SCCA legal way to run
a lighter flywheel on a stock engine and not get bumped up a class. All the hot shoes back then
did it.

I'm sure it has some negative affects but thats why I have 2 more 12As apart in the garage now.

Nice to hear how well it turned out for you Robert.

project7s

iTrader: (5)

That is odd that a rb flywheel would be out of balance. Of any of the flywheel companies I would have guessed theirs to be perfect.
I have an aluminum rb flywheel in my rb Holley equipped 12a and its really smooth, in fact is gone to 8k a couple times on accident, getting caught up in the moment.

diabolical1

iTrader: (3)

so what exactly did you send? wasn't the flywheel included?

Siraniko

iTrader: (13)

I was wondering about the same thing. In addition, if the internals are matching from an original block, it should be balanced and balancing is pointless unless your hitting redline most of the time

rwatson5651

iTrader: (5)

Yes, it was included, I sent them everything, eccentric, both counter balance weights, etc, etc.

According to my guy it was about 5 grams out of balance. He didn't seem surprised. The pressure plate was 8 grams out.

Also, my guy went to the trouble to balance the whole assembly to less than .1 gram, (I was watching him so I think he went to extra measures showing off, the last few tenths took longer than the last five grams did). Maybe it was not that it was too far out that made the difference, but rather that my guy balanced the whole assembly and to a very high degree of balance. Who knows?

rwatson5651

iTrader: (5)

It was not from an original block. New SE housings, new 89 NA rotors, old school eccentric, and then the RB flywheel. I know that in theory it could have been put together without balancing, but since I had noticed the last motor was not has smooth as the factory 12a and I knew it would spend a lot of time at higher rpms I was taking extra measure to try to get the smoothest motor I could and even tough it took the extra balancing of the flywheel with the pressure plate attached to finish it off I have ended up with a motor that is even smoother than I remember the original 12a to be, so I don't consider it pointless, I have just never felt one this smooth so I am happy!!