Valve AdjustmentProper valve adjustment is critical for quiet and efficient operation of a flathead six and is the first line of defense against burned valves. Compared to overhead valve engine the flathead is a very simple design. A tappet follows the contour of the cam lobe pushing a valve up and open at the appropriate time. The only adjustment is the clearance between the tappet and valve stem. Accurate adjustment can only be made while the engine hot. To complete the job you will need a valve gasket set, set of go/nogo feeler gauges, pair of tappet wrenches and a pair of gloves to protect you from burns on the exhaust manifold. While the valve covers are readily visible from the top of the engine, don’t attempt this job from above the manifold. Instead raise the right front on a jack stand and remove the right front tire. Inside the wheel well is an access panel approximately 3 feet wide and 18 inches high. Remove the bolts holding the access panel. When removed you will have straight on access to the valve covers. Start the engine and bring it up to operating temperature. After the engine warms up, stop the engine and manually turn it over to Top Dead Center (TDC). Verify piston #1 is in firing position by checking the position of the distributor rotor. If should point around 7 o’clock. If it points to the 1 o’clock position, you have piston #6 in firing position. Manually turn the engine one full revolution and you are ready to start. Remove the valve covers and use the following sequence for the order of the valves to adjust. Exhaust valve clearance .010Intake valve clearance .008 Stage A, #1 and #6 at TDC, #1 in firing positionStage B, #1 and #6 at TDC, #6 in firing position To move from Stage A to B, manually turn the engine 1 revolution. Stage A – Adjust #1 Both valves, #2 Inlet valve, #3 Exhaust Valve, #4 Inlet valve, #5 Both valves. Stage B – Adjust #2 Both valves, #3 Inlet valve, #4 Exhaust valve, #5 Inlet valve, #6 Both valves.
Using the two tappet wrenches you can use one hand to adjust the tappet, leaving the other hand free for the go/nogo gauge, The go/nogo gauge has three steps cut into it. If the adjustment gap is too wide, you will be able to slide it to the third step. If the gap is too narrow only the first step will slide between the valve and tappet. What you want is the middle step to fit snugly. Adjust each valve as specified in the adjustment sequence. It is better to err on the side of too much clearance versus not enough. Too much clearance may result in a slightly noisy tappet, while too little may burn the valve. After you finish the adjustment, reinstall the valve covers with the old gaskets. Bring the engine back up to operating temperature and you will notice the engine is much quieter. Sometime you will need to readjust a single noisy valve. Just make sure it is fully off the cam lobe and totally closed. If everything is OK remove the valve covers and install the new valve cover gaskets (780-469) with sealer. When re-tightening the valve covers don go overboard. They just need to be snug, letting the gasket and sealer do the work. Too tight distorts the sheet metal cover and usually results in leak. Reinstall the access panel and tire and you are back on the road. Properly adjusted valves result in a quiet running engine and help protect against damaged valve train components. If you have done the job right it will be difficult to tell if the engine is running from five feet away because it so quiet!