have you had oil pump to bits,,, I rebuilt my engine new valves ,cam followers, lifters, guides,, bolted all together expecting it to fire up,,,, span over like it had no or little compression ,,, tried towing it for miles , no wouldn't try to start ,,took it to a friends who had a ramp in his garage , off came head couldn't see nothing wrong , took sump off ,, pistons out ,timing on and off double checking after double checking , still nothing , for days scratching our heads, took engine side cover off ,, my mate had rebuilt oil pump wrong way round ,,, so squeezed all lifters, any that didn't spring up , went in bin built all back up , timing ,back on , turned key started,,, it was the oil pump which my fiend had stripped to check was ok , put cog wrong way round, which wasn't pumping oil too the lifters so valves wasn't working , worth a try,,, before you kick it a few times,,,,