methodical wrote:
On your brothers machine, why was the decision made to cut the base of the cylinder down? Has the deck been cut at all? You mentioned the porting and exhaust eye brows, has the exhaust duration been changed other then cutting the cylinder base down?
1) I do not know why they decided to cut the base of the cylinder down.
I bought two of my machines in the USA and this was one of them. I have no history on the
Engine or the machine.
All I know is that it is goddamn fast. The dyno runs at the airport proved it. It still pulls hard at 60mph. It loves rpm.
2) It does not appear the deck was cut.
3) I don't know if exhaust duration has been changed. But I doubt it. Looks stock except for those "eyebrows"/cats eyes.
When I first bought these machines I knew NOTHING about oddy's. I blew up this particular Engine 6 times before I figured it out. You will notice the beautiful smear of liquid aluminum on the cylinder in the pictures below.
4) In the pictures below you will see that the base was obviously cut down 2mm because the webbing on the cylinder base is noticeably smaller than the stock one on the left. It's the picture with the straight edge.
Also seen is the cats eyes (eye brows) exhaust port.
5) My brothers built Engine had 173 psi compression after the fresh rebuild
An Engine with my homemade head had 153 psi compression
My Engine had 140 psi compression
6) Once I switched to AVGAS all of my problems just disappeared.
It was like penicillin -- Insta cure. That's why I'm always yapping about it.
CO
Edit #1: I had to think about this for a while.They cut down the cylinder base to gain intake timing (about 11 degrees based on my calculations). I may be wrong though on this theory.
I say you gain intake timing because the piston don't suck the reeds open until it goes up.
By lowering the jug you have lowered all exhaust, transfer and intake timing together.
BUT you gain on the intake timing 11 degrees because it opens sooner because the jug is lower.
Am I on smoke for thinking this way ???
CO