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View Full Version : tdc -> tdc crank degrees ?



MartianBob
01-25-2008, 07:32 PM
I'm verifying lifter preload.
How many degrees of crank rotation from tdc of one piston to the next tdc?

Thank you
Bob

cdchicago
01-26-2008, 02:11 AM
I have yet to take my bottom end apart but being a 6cyl I should think there are 3 crank throws 120 degrees apart with 2 rods each. So i would suspect 60 degrees apart. Or 360/6=60.

Hope this helps

Mike8675309
01-26-2008, 01:55 PM
Sounds right.
This diagram should help visualize that.
http://www.frontiernet.net/~miketoni/images/tbird/DISnostart/DISTimingDiagram.gif

MartianBob
01-26-2008, 11:14 PM
t should have been more obvious to me. I wasn't sure if all cylinders fired on every crank rotation, but if #1 does then the rest of them do to - duh. It's all good now, .060 of shims and the preload is just over half a turn.
Thank you for the replies.

Cheers
Bob

XR7 Dave
01-26-2008, 11:20 PM
Actually each cylinder only fires every other revolution so TDC compression occurs every 120 deg crank rotation.

And our motors have 6 rod throws, none are paired.

cdchicago
01-28-2008, 05:11 AM
Damn someone caught me before i could fix it.

Seems i got to thinking about math and forgot the fundamentals of 4 stroke engines. suck, squeeze, band and blow. it takes 2 crank revolutions!

So 720/6 = 120.

I didn't know that there were 6 throws, thanks Dave.

Chris