Question 1

What steps must be taken to prepare piston/connecting rod assemblies for inspection on Pontiac Fiero?

Accepted Answer

However, before the inspection process can be conducted the piston/connecting rod assemblies have to be cleaned and the original piston rings have to be taken off the piston, new piston rings should be fitted during the assembling process. There should be use of a piston ring installation tool while removing the rings so as not to cause damage on the pistons. Finally, every speck of carbon must be removed from the crown of the piston with a hand-held wire brush or fine emery cloth; wire brush operated with a motor drill is to be avoided because the material of the piston is very soft. There should be a piston ring groove cleaning tool which cleans the carbon deposits on the grooves A piece of an old ring can be used if the groove cleaning tool is not available but it has to be done cautiously so as not to manufacture grooves on the surface. After surface cleaning the piston/rod assemblies should be dried appropriately and then examined to ascertain if the oil return holes are open. In the case that the pistons are not worn out or damaged in such a way that they cannot be restored through hone and sizing then new pistons will not be needed. Every piston should be checked for crack or score or scuff or hole or burnt area as such defects show that the engine might have overheated or combusted abnormally and the cooling system as well as the lubrication system should then be checked. Some signs of rusting were observed predominantly as pits and therefore may have been attributed to leakage of the coolant into the combustion chamber which will need to be fixed in future to avoid such occurrences. The piston ring side clearance should be gauged using a feeler gauge, the measurement should be taken at four points around the groove and in the case that the clearance is beyond what is allowed, then new pistons will be needed. The bore and piston diameter have to also be measured to check the piston-to-bore clearance to ensure that they are matched; if there is excessive clearance then rebore and new pistons are required. Rocker / piston-to-rod clearance are to be determined by rotating one part in one (piston) direction and the other (rod) in the opposite direction; the end play felt is the clearance, and should show a significant amount of play to warrant adjustment. If pistons have to be replaced because of worn out or damaged ones or if the pins are loose, then they should be taken to an automotive mechanics for renewal or reconditioning of connecting rods should also be taken for rectification of such flaws as bentness. Last but not the least, the connecting rods must also be checked for any signs of cracks and damages; the old bearing inserts have to be removed and cleaned thoroughly but for this purpose, they can be temporarily unbolted and taken out.

Question 2

What steps must be taken to prepare piston/connecting rod assemblies for inspection on Pontiac Firebird?

Accepted Answer

Before inspection can be made, the assemblies have to be thoroughly washed and the original piston rings have to be taken out of the pistons, and always replaced with new ones. Carefully extract the rings from the pistons by employing piston ring installation tool, bezel or any other means which do not mar their surface. When most of the deposits have been removed, use a hand-held wire brush or fine emery cloth to scrape all signs of carbon from the top of the piston; this must not be done using a wire brush affixed to a drill motor because it will undermine the material of the piston. To remove the carbon from the groove use a piston ring groove cleaning tool or you can use one of the pieces you cut from the old ring, but make sure did not take any metal out and damaged the groove. Subsequent to the withdrawal of the deposits, the piston/rod assemblies should be cleaned suitably with solvent and dried to make certain that both the oil hole at the big end part of the connecting rod and the oil return holes at the ring groove zones are free from obstruction. Therefore it may not be necessary to replace pistons if pistons are undamaged or if engine block is not rebored; there was found even vertical wear about the thrust surfaces and slight looseness of top ring only. Examine each piston for cracks, scores, scuffs, holes, and burn areas since such conditions point to overheating or odd combusting, and so require a comprehensive examination of the cooling and lubrication systems. Pitting was observed and was probably due to coolant leakage which has to be rectified so that it cannot reoccur in the rebuilt engine. The piston ring side clearance can be measured with a new piston ring installed and a feeler gauge across several locations around the groove planes and the appropriate ring must be used in a groove; if the readings are high a new piston or set of rings might be needed. Check the piston-to-bore clearance by comparing the bore and piston diameter and calculate the clearance; if found tag high should rebore the block and new pistons along with the rings. Feel the piston-to-rod clearance by rotating both the piston and the rod in opposite directions; if they have much wiggle, this is a serious wear that has to be taken care of: in most cases, Piston/connecting rod assemblies are usually taken to an automotive machine shop since it must be done by replace piston pins and rebore. If ever pistons require to be replaced due to worn out connecting rods or if the piston pin has excessive play, these have to undergo a bending and twisting check on an automotive machine shop. Last but not the least, one must look for the cracks and damage in the connecting rods by lifting the rod cap but not to remove it, feel around the bearing surfaces for nicks and Scratches and then replace the bearings with the old ones and tighten the cap.

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