Quote:
Originally Posted by Ol' Ron
The biggest problem with the long stroke is piston speed. As the valve opens it shouls reach max lift at about 70 degs after TDC. This is when the piston is reaching max speed. the valve begins to close at around 135 degs and the piston begins to slow down. At very high RPM's the piston runs away from the intake charge, effectively de-stroking the engine. I di believe a pop-up piston will breath better. There are a coupla things you can do to do this without spending allote of money. Using a 3 3/4 strole piston on a 4" crank, then recessing the piston .125 into the head. Now remove the lip created by the transfer area. This can give aprox 9:1 in a 276 engine. After you build a few dozen engines, you'll learn allote.
Good luck.
PS Just remember, ALL the power the engine makes has to come through those ports.
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If you say "high RPMs" how high are we talking?
The 4 1/4 x 3 3/8 with the Potvin 425 won`t stop revving....
Have no tach but for a Flathead it revs high....
The 4 3/8 x 3 5/16 i would build as a torque motor anyway...
with a 404A for example....
That popup 276 sounds like a good Idea
Do build that often?
Which heads can take a 0.125 CC cut?
I know Sharp can but they are hard to come by....