Mercury YF7Z-6250-AA Camshaft

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Begin by removing the valve cover(s) to access the camshafts and then remove timing chains, camshaft sprockets, and spacers. Measure the thrust clearance of the camshaft(s) with a dial indicator. If this is beyond the required value, instructions suggest changing the cylinder head or even the camshaft. Ensure correct reassembly of gathered-together cap clusters of bearing surfaces, Pay attention to specific bolts. Very carefully, lift off camshafts from the cylinder head taking care not to mix up any components. Do the same for another one. Visually check all lobes and bearing journals for signs of wear during an inspection. Use a micrometer to measure the diameter of the camshaft journal and lobe lift. Utilizing plastigage, oil clearance was checked for each camshaft journal. Inspect and clean the oil feed tube as well as a reservoir in the timing chain tensioner. The surfaces of both lobes and bearing journals should be liberally coated in moly-base grease or camshaft installation lube.

To check cam lobe wear, remove valve covers and position number one piston at TDC on compression stroke. Mount dial indicator on engine, align with first rocker arm, zero indicator, and slowly turn crankshaft to determine max cam lobe lift. Record figures for each valve by repeating process across cylinders. Compare results to specifications, and if lift is less than specified, replace camshaft. For removal, remove pushrods, valve lifters, timing chain, camshaft sprocket, and radiator. Check camshaft endplay, replace thrust plate if necessary, and remove camshaft using long bolt. Inspect camshaft for wear, pitting, and seizure. Measure bearing journals for wear or out-of-round conditions, and check camshaft lobes for discoloration, score marks, or chipping. If lobes are in good condition and measurements are within spec, camshaft can be reused. If bearing replacement is required, use special tools and follow instructions for removal and installation. Lubricate camshaft and bearing journals with engine assembly grease, then carefully slide camshaft into engine. Apply moly-base grease or assembly lube to both sides of thrust plate and install on block. Tighten bolts, and follow appropriate sections to reinstall lifters, pushrods, rocker arms, timing chain/sprocket, timing chain cover, and valve covers. Complete remaining installation steps in reverse order, change oil, and install new oil filter before starting engine.

To verify camshaft lobe lift and to know how much is worn, one has to do the following; Firstly, remove the valve covers. Place the first piston at TDC on the compression stroke and put a dial indicator on the cylinder head; the plunger of this indicator must seat onto the first rocker arm. Retrace the amount on the dial indicator and rotate the crankshaft in the normal direction until the dial stop, when the needle of the indicator starts moving in the opposite direction, then the maximum cam lobe lift will be noted. This measurement should also be recorded and the piston moved back to the TDC position, the dial indicator moved to the remaining number one cylinder pushrod for the other result of each valve to be recorded. Repeat this for the other valves which, when are properly aligned all pistons should be on the compression stroke and in line with the firing order. Upon doing the checks, make the comparison with the specifications; in the case of camshaft lobe lift being lower than the specified value, this is an indication of wear and hence the need for a new camshaft. For dismantling, properly withdrew the pushrods, valve lifters, timing chain, and camshaft sprocket, and the radiator too is to be removed. Measure the camshaft endplay with a dial indicator; if it measures more than standard, replace the thrust plate each time you reinstall it. Take out the camshaft thrust plate bolts and then using a long bolt you will withdraw the cam from the block without straining the bearings. Post removal, be sure to wash and examine the bearing journals for wear or harm; if harmed, both camshaft and bearings will need replacement-they are tricky to replace without the help of an expert. Check for wear by measuring the bearing journals and analyse the camshaft lobes for any discoloration or damages; if none they camshaft can be reused. For the bearing replacement, tools and skills are required, thus, it is advisable to take the block to an automotive machine shop. In the case of the camshaft, one must coat the bearing journals and lobes with assembly grease, than push the camshaft into position, and apply grease to the thrust plate before final tightening down. Failure of these goes in the reverse order of their removal when you are reinstalling the lifters and the pushrods before the rocker arms, the timing chain, and finally the valve covers. Last but not the least, replace the engine oil and also fit in a new oil filter before turning on the engine.

Visually examine the cam lobes and bearing journals for score marks, pitting, galling, and evidence of overheating. Look for flaking of the hardened surface of each lobe and inspect the bearing surfaces of the camshaft cap clusters for signs of excessive wear, damage, or overheating.

Mount a dial indicator on the engine and position the plunger in-line with and resting on the first rocker arm.

Rotate the crankshaft 45-degrees counterclockwise (as you are facing the engine) from TDC. This will place the crankshaft keyway in the 9'o-clock position, ensuring that all pistons are below the level of the block deck to avoid any valve contact.

Lubricate the camshaft bearing journals and cam lobes with camshaft installation lube.

Use a dial indicator to measure the thrust clearance by prying the camshaft gently forward and back.