Determining top dead center

   

   

You'll need to get everything out of the way so you can work on the harmonic damper ring. Remove the fan, belts, shroud and water pump pulley. You may have to remove the water pump to gain full access to the damper ring and do the measuring needed for this operation. This would be a good time to replace the pump anyway. Pumps and gaskets are not that pricey. Whether or not you replace it, remove the pump and check for impeller slip on the pump driveshaft. Hold the impeller with one hand and the drive hub of the pump in the other hand and twist in opposite directions. I have encountered overheating and found this problem....FINALLY....after much head-scratching. Even if the pump is good, you may at this point want to replace it with a good, high-flow unit. Flowkooler, Stewart and Edelbrock are names that come to mind, there may be others who produce a quality high-flow pump. A good high-flow pump is nearly MANDATORY on a 400 SBC or any other motor which uses siamezed cylinders.  

You'll need to get everything out of the way so you can work on the harmonic damper ring. Remove the fan, belts, shroud and water pump pulley. You may have to remove the water pump to gain full access to the damper ring and do the measuring needed for this operation. This would be a good time to replace the pump anyway. Pumps and gaskets are not that pricey. Whether or not you replace it, remove the pump and check for impeller slip on the pump driveshaft. Hold the impeller with one hand and the drive hub of the pump in the other hand and twist in opposite directions. I have encountered overheating and found this problem....FINALLY....after much head-scratching. Even if the pump is good, you may at this point want to replace it with a good, high-flow unit. Flowkooler, Stewart and Edelbrock are names that come to mind, there may be others who produce a quality high-flow pump. A good high-flow pump is nearly MANDATORY on a 400 SBC or any other motor which uses siamezed cylinders.  

Anyway, back to the task at hand. First use solvent and then hot soapy water to thoroughly clean the harmonic damper and timing pointer. Remove the valve cover for #1 cylinder and back off the rocker arms for both valves for that cylinder. COUNTING THE NUMBER OF TURNS YOU LOOSEN THE ROCKER NUTS WILL MAKE IT A SNAP TO GET NEAR TO THE CORRECT LASH WHEN YOU TIGHTEN THEM BACK AFTER THIS OPERATION. Disabling the valves by backing off the rocker arms will prevent interference between the timing tool probe and the valves while turning the crank. Turning the motor over by hand will be easier if you remove ALL the spark plugs. With a socket on the damper retaining bolt or using the tool described and a long socket handle, rotate the crankshaft clockwise while your buddy uses a stong flashlight to look into the #1 spark plug hole. Bring the piston up to top dead center, then continue rotating the crank very slowly so that the piston comes down in the bore slightly. You want the piston slightly past top dead center down in the bore, but not so far down in the bore that the probe of the top dead center tool will not contact the piston crown. At this point, we are not concerned with where the crank/piston is in the total 720 cycle of operation. In other words, we have the valves disabled, so it doesn't matter whether you are on the exhaust cycle or the compression cycle as the piston comes up to TDC. All we are working with at this point is the 360 degrees of the damper, regardless of the cam and valves. Screw the top dead center housing into the spark plug hole and snug it down. Insert the probe of the tool into the tool housing and screw it in until you feel resistance of the tool probe against the piston crown. Snug it down slightly against the piston crown and start from there.  

Anyway, back to the task at hand. First use solvent and then hot soapy water to thoroughly clean the harmonic damper and timing pointer. Remove the valve cover for #1 cylinder and back off the rocker arms for both valves for that cylinder. COUNTING THE NUMBER OF TURNS YOU LOOSEN THE ROCKER NUTS WILL MAKE IT A SNAP TO GET NEAR TO THE CORRECT LASH WHEN YOU TIGHTEN THEM BACK AFTER THIS OPERATION. Disabling the valves by backing off the rocker arms will prevent interference between the timing tool probe and the valves while turning the crank. Turning the motor over by hand will be easier if you remove ALL the spark plugs. With a socket on the damper retaining bolt or using the tool described and a long socket handle, rotate the crankshaft clockwise while your buddy uses a stong flashlight to look into the #1 spark plug hole. Bring the piston up to top dead center, then continue rotating the crank very slowly so that the piston comes down in the bore slightly. You want the piston slightly past top dead center down in the bore, but not so far down in the bore that the probe of the top dead center tool will not contact the piston crown. At this point, we are not concerned with where the crank/piston is in the total 720 cycle of operation. In other words, we have the valves disabled, so it doesn't matter whether you are on the exhaust cycle or the compression cycle as the piston comes up to TDC. All we are working with at this point is the 360 degrees of the damper, regardless of the cam and valves. Screw the top dead center housing into the spark plug hole and snug it down. Insert the probe of the tool into the tool housing and screw it in until you feel resistance of the tool probe against the piston crown. Snug it down slightly against the piston crown and start from there.