Mercury F3AZ-6108-CB Piston

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Before the piston and connecting rod assemblies can be removed, the cylinder heads, oil pan and oil pump have to be taken off on 5.0L engines depending on the type of engine that will be overhauled. First, look for any sharp edges at the extremes of ring travel, the ring travel and those should be gotten rid of by use of a reamer before you attempt to remove the piston and connecting rod assemblies since tearing of the pistons may occur. After that level off the ridges turn the engine upside down in such a way that the crankshaft is on the top. Measure the endplay of the connecting rods with the help of dial indicator or feeler gauges; if the endplay of the rods is more than the service limit specified, then it may be necessary to fit new connecting rods. Label the connecting rods and caps to distinguish them from one another; alternatively, back off the cap nuts the last half turn before they are ready to come off. Withdraw the connecting rod cap together with the bearing insert-be careful not to let the bearing insert fall. When the connecting rod has studs with nuts, it is advisable to cover the crankshaft journal and cylinder wall with plastic or rubber hose in order to remove the piston. Force the complete connecting rod and piston assembly out through the top of the engine by means of a wooden or plastic hammer handle respectively , and make sure that all ridges are got rid of. Proceed in the same manner for each of the other cylinders which are also present in the apparatus. Upon removal, align and replace the connecting rod caps and bearing inserts back into the rightful rods fastening the cap nuts loosely so as not to harm the bearing of the rod . As it will cause difficulty in reassembly of the pistons with the connecting rods retain the two as a single unit.

No, new pistons may not be necessary, but new piston rings are recommended for engine rebuilding.

Rotate the crankshaft to check for binding - Compare the measurement of the connecting rod endplay to specifications - If necessary, resize the rods at an automotive machine shop.

You should gradually loosen the connecting rod cap nuts or bolts and remove them by hand.

Remove the connecting rod cap and bearing insert together. On 4.6L engine connecting rods, the method used to manufacture and machine the rod cap is unique; they "fracture" (break) the cap from the rod to give a perfect match upon reassembly. Don't drop the bearing insert out of the cap.

Rotate the crankshaft a number of times by hand to check for any obvious binding.

Check the piston-to-bore clearance by measuring the bore and the piston diameter. Measure the piston across the skirt, at a 90-degree angle to, and in line with, the piston pin. Subtract the piston diameter from the bore diameter to obtain the clearance. If it's greater than specified, the block will have to be rebored and new pistons and rings installed.

Check the piston-to-rod clearance by twisting the piston and rod in opposite directions. Any noticeable play indicates excessive wear, which must be corrected. The piston/connecting rod assemblies should be taken to an automotive machine shop to have the pistons and rods resized and new pins installed.

With the notches on top of the piston facing the front of the engine, gently insert the piston/connecting rod assembly into the number one cylinder bore and rest the bottom edge of the ring compressor on the engine block.