twincam engine rebuild

[tcsoar]

Hi,

I have almost finished putting my engine back together, the rebuilt head is back on the block. I have noticed now though that each cylinder sucks in the tape over the inlet ports during its induction stroke as expected, but blows back out on the tape as it moves over to its compression stroke.
Can anyone let me know if this is normal.
I can still feel the compression for each cylinder when I turn it by hand.
I have also checked the cam timing and valve clearances and these all appear to be correct.

Anyone have any ideas

Thanks,
Chris.

[ppnelan]

See Section 'E' Fig.5 in the Workshop Manual - the inlet valve (inner circle) remains open for a 'considerable' part of the compression stroke. When it is running, this allows the momentum of the incoming fuel/air mixture to push a bit extra into the cylinder. When it is turned over by hand, you will feel it push back out the inlet port over this part of the compression stroke.
As long as you have compression and the valve timing, etc is in order as you have noted, don't worry - be happy!

Matthew

[ppnelan]

P.S. It's called 'valve overlap'.

[tcsoar]

Thanks for that, and dont worry, it made me happy!!
Going away for a few days and i knew it would be niggling away at me, so know i can relax.
Thanks again,
Chris.