I'm trying to set the valve tappet gap on our D17 Series 3 Gas burner. My book shows that I should move the #1 cylinder to TDC and set the gaps on valves 1,2,4,& 6. Then set the #4 piston to TDC and set the gaps on valves 3,5,7,&8. First question - confirming the cylinder numbers start with #1 closest to the radiator and move towards the steering wheel 1,2,3,4. Second Question - It appears to me that the #1 & #4 cylinder are both at TDC at the same time? I am unable to set the gap on valve #3 & #5 as there is no gap even with the screw backed all the way out. That's making me think I'm making a mistake.