Here are early and late type Merc deflector pistons
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Here are early and late type Merc deflector pistons
And here is a Quincy Looper piston.
Christner actually first advertised them as "American Flat tops". From this image you can see why.
If you can excuse my really horrible art work this is the intake flow pattern thru a deflector Merc. The green thing is the cylinder intake (or transfer) port, the red is the exhaust port, the black thing at the top is the spark plug. The blue line represents the intake charge following the intake passage, entering the cylinder, bumping into the deflector ridge on the piston and turning up to sweep thru the cylinder. With the shape of the intake passage (under the letter "A") pointing straight across the piston dome toward the exhaust port the charge would short circuit right out the exhaust if it were not for the deflector ridge on the piston.
No big deal, but I think that (Picture of a Quincy Piston) is a Levendusky piston for a Quincy.... My reason, I thought Stan Levendusky lightened his pistons above the wrist pin....
My dad didn't tlike the lighter pistons as he like to use a heavy piston to take the heat out of the cyclinder....but loopers were so new to us....we couldn't figure out how the gas knew where to go in those cyclinders as they had so many holes...
The only award this next image will ever win is for complete crudeness.
The important thing to notice is at point B the intake port and passage behind it are shaped to direct the incoming charge of fresh air and fuel up into the cylinder without having to bump into a deflector on the piston.
This allows the piston to be flat.
I don't know who made that piston. If we could get Stan Jr on here, he would be the expert on that. I will try to look him up and invite him.
The advantages of the deflector arrangement are that it is really easy to make at the factory and the resulting motor has lots of mid and low rpm ooompff to push a boat over plane and pull skiers, etc. Very good results for pleasure and work motors.
The disadvantages are that the motor won't have much top end power and the piston will be heavy which is another factor that restricts rpm. The real killer is that the top of the piston has a lot of surface area .... much more than the surface area under the piston. Heat enters the top and can not leave the bottom .... under heavy load the piston accumulates heat until it melts :(
With a bunch of special high speed photography they actually figured out that if the ports and passages are correctly shaped and postioned the incoming gases not only squirt up into the cylinder .... but they can even loop around thru themselves before heading toward the exhaust port.
Something sort of like this:
(OMC had some really nice graphics in their brochures when the 49 ci triple came out; I'll dig them up and post them soon)
http://www.screamandfly.com/home/mul...s/images/5.jpg
borrowed from screamandfly :)
This engine shown on thread #6 is a Quincy D Looper once owned by Ron Howard.(not sure of the first name). It now belongs to Schultz Racing Team.Quote:
Originally Posted by David_L6
It was completely gone through and reassembled by Homer and Tim Schultz for this O.F. Christner race. Had it mounted on an Sidson cloth deck hydro.
Motor ran great except it was sucking water in the crankcase. One of the Quincy Welding race team members told us that we needed a double seal on the lower end cap.
The engi9ne is now on display at Schultz Marine.
MAN.....!!!!!! Talk about a conversation piece.
Jeff - The cops never bothered us much about noise during dyno runs unless we tried to push it past 10pm or so. Most of the noise issues were related to on-water testing. We'd have to call the conservation agent and let him know we were going to be running on Quincy Bay. As the engines became louder, due mainly to the bigger megaphones, the bayside residents became less tolerant. Especially when we would "forget" to call the agent. Hence, the big push for closed exhaust systems, water injection, etc.
Frank