I just stumbled upon this thread today, 9 mo. late! I have had some exposure to the prototype 550's and can share the following:
in general: prototype engines were #'d 547xx, there were less than 20, probably about 12-13. They varied considerably in spec's, including castings. At least 1 (-10) had a 72.5MM bore (1089.86CC)
Jan6, Jacques: eng. # 557-07 was in 550-10, NOT "010". There never was a 3-digit 550, or 550A. It is a "3rd series" engine, with "no bump" intake covers, and DCM carbs. I am told that it is now "on a shelf" and the car has a 905xx series engine in it. Photos I have seen of the engine leave some question in my mind as to how "orginal" it is.
Joris, Jan.6; Engine in 550-09 is a 905xx series engine, which I bought from Vernon, and brokered to a Japanese client. Years later, car was in Mexico, and owner sent the engine to Vern for rebuild. It was well-worn, and I believe did get a set of Jacques pistons. Car is now in Sweden. Chassis data plate states that the original engine was 547-10, 1089CC. Car came with info indicating that ar was raced at Sebring in 1955 w/ 1089 eng. I suspect that this is the eng. Ken Miles talks about, converting to 1498CC and racing forcefully for many miles before it comprehensivily exploded.Vince Bobba told me of seeing "1100 parts" sold from Ca. to Europe some years ago, but could (or would?) not provide more info.
Al H. Jan 6; engine pictured is NOT a prototype ("bump" heads)
Jack W.; Car is 550-0022 NOT -022. Again, There NEVER was a (5 OOP'S)(edit) 3-digit 550!!!
NOTE: Just fun trivia, not earthshaking, not effecting values ,not intended to denagrate, question, or hurt anyone, just my opinion.
Last edited by Gerry McCarthy on Sat Sep 29, 2012 2:34 pm, edited 1 time in total.