Hello,
done some research in my archives and found this in a ReoClub Pdf:
The 8-25 and 8-21 Flying Cloud 8s relied upon the 5-main bearing, 268 cubic inch, 90 hp Continental R-800 designed and produced for REO by Muskegon’s Continental Motors. Both engines were state-of-the-art designs and utilized modern aluminum pistons, counterbalanced crankshafts and were both statically and dynamically balanced.
Hope this was usefull.
best regards