Thanks. I found his thread & that really sucks, I just ordered mine at the last sale.

 

Tingram the valves are not open at TDC, they are opening and closing as the piston is going up or down.

 

i understand that, but when the exhaust valve is closing the piston is chasing it, i know on or pulling tractors you have to be very careful or they will hit the piston, you can change the centerline as little as a degree and make contact with the piston, and depending on the cam grind the intake valve opens usually just a little bit before tdc.

 

I think on the Helix 2 there is less lift on the exhaust valve but more duration.