Built a new motor a few months back. Bolted together the bottom end and bolted the recon head down, had the block at no1 TDC, placed the cam in the journals at no1 TDC, BUT as i tightened down the rockers the cam rotated (maybe 20deg?) without me noticing till the rockers were all torqued down. I tried to turn the crank but it was stuck!! It did turn eventually after a longer bar was found. Stupid me didn't think much of it at the time, kept on going, bunged the motor in, and it's run fine for 6 months.

BUT it blows smoke on decell. would this be the cause? i.e. bent valves or cracked guides? whats the most likely damage? or what else could cause this smoke?

Cheers.

If you believe google - valve guides