GM 10146900 Crankshafts

The crankshaft can only be removed after the engine has been removed from the vehicle. It is assumed that the flywheel or drive plate, crankshaft balancer/vibration damper, timing chain, oil pan, oil pump, and piston/connecting rod assemblies have already been removed. The rear main oil seal/housing (Quad-4 only) must be unbolted and separated from the block before proceeding with crankshaft removal. Before removing the crankshaft, check the endplay. Mount a dial indicator with the stem in line with the crankshaft and just touching one of the crank throws. Push the crankshaft all the way to the rear and zero the dial indicator. Next, pry the crankshaft to the front as far as possible and check the reading on the dial indicator. The distance it moves is the endplay. If it is greater than specified, check the crankshaft thrust surfaces for wear. If no wear is evident, new main bearings should correct the endplay. If a dial indicator is not available, feeler gauges can be used. Gently pry or push the crankshaft all the way to the front of the engine. Slip feeler gauges between the crankshaft and the front face of the thrust main bearing to determine the clearance. Check the main bearing caps to see if they are marked to indicate their locations. They should be numbered consecutively from the front of the engine to the rear. If they are not, mark them with number stamping dies or a center punch. Main bearing caps generally have a cast-in arrow, which points to the front of the engine. Loosen the main bearing cap bolts 1/4-turn at a time until they can be removed by hand. Note if any stud bolts are used and make sure they are returned to their original locations when the crankshaft is reinstalled. Gently tap the caps with a soft-face hammer, then separate them from the engine block. If necessary, use the bolts as levers to remove the caps. Try not to drop the bearing inserts if they come out with the caps. Carefully lift the crankshaft out of the engine. It may be a good idea to have an assistant available since the crankshaft is quite heavy. With the bearing inserts in place in the engine block and main bearing caps, return the caps to their respective locations on the engine block and tighten the bolts finger tight.

Assuming the prior cleaning, inspection, and potential repair or reconditioning of the engine block and crankshaft, the first step in engine reassembly is the installation of the crankshaft. Remove the main bearing cap bolts with the engine positioned bottom-side up and carefully lift out the caps, ensuring their proper order for later installation. If original bearing inserts still remain in place on the block and caps then remove them from there before carefully cleaning lint free cloth. The cleanliness should be maintained at all costs during this process. Those inserts should be cleaned by raking off any build-up on their back surfaces before one insert is placed into each main bearing saddle in this block while another one goes into its corresponding main bearing cap. For correct positioning, make sure that grooved insert is oriented properly in block and tab on bearing insert must align with recess in block or cap. Moreover, oil holes in block have to match those provided for bearing inserts. Depending on the engine type, flanged thrust bearing should be installed at designated cap and saddle location. Additionally, clean faces of bearings in block and crankshaft main bearing journals. Finally, lay it carefully into position in main bearings with taking care to verify cleanliness of crankshaft as well as measure clearance of main bearings oil. For measuring this clearance, Plastigage is used by putting pieces on each crankshaft main bearing journal and installing caps without destroying Plastigage. As always take care not to rotate crankshaft while tightening main bearing cap bolts stages should work from center mains outwardly. When caps are removed compare width of crushed Plastigage with scale provided to determine if it meets specifications for oil clearance of main bearings. If these values are different then some other types of bearings may be needed instead. Clean all traces of Plastigage material from main bearing journals and also their respective faces if need arises again as a part of final crankshaft installation lift out engine followed by cleaning bearing faces in block, applying uniform layer moly-base grease or engine assembly lube on bearing surfaces (including thrust faces) and laying crankshaft back in place. Apply lubricant to the faces of the bearings in the caps and install them in their original locations with the arrows pointing forward. After that, progressively tighten bolts, tapping gently on the ends of crankshaft to align main bearing with crankshaft thrust surfaces. All main bearing cap bolts should be retightened and the crankshaft should be rotated manually to check for any binding. Finally check this by feeling endplay with feeler gauges or dial indicator before installing new rear main oil seal.

Use a scraper, stone or file to eliminate all the burrs from the oil holes in the crankshaft; this is equally important; at the same time, chamfering them will remove any sharp edges that might damage new bearings. Examine the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks. To ascertain its condition, rub a penny across each journal several times-if copper rubs off it and adheres to the crankshaft, the journals require regrinding. If possible, use solvent to clean it before drying it up with clean compressed air. The rest of the crankshaft needs to be magnafluxed for hidden cracks-this should be done by an automotive machine shop. Use a micrometer to measure main and connecting rod journal diameters while taking measurements at different points around each circumference to determine roundness of out of roundness. If damaged, tapered, out-of-round or worn beyond specified limits in specifications given have the automotive machine shop reground your crankshaft.Check both oil seal journals at either end of the crankshaft for wear or damage. In case there are grooves on the journal worn by seal's rubbing or it is nipped/scratched then when again putting back together engine there may be leaking from new seal.Repairing this shaft can sometimes involve pressing on a thin sleeve at an automotive machine shop.If not possible replace with a new or used one replacing.Quad-4 engine builders must inspect their oil pump drive gears for signs of wear or damage.If you need a replacement you will have to bring your crankshaft to a dealer service department or an automotive machine shop.The old gear has been drilled and chiseled off while prior installing into an oven was heated up by another new one.Take time as you also do some examination on inserts for both main and rod bearings.

The crankshaft and main bearings are best taken out with the engine out of the car and no one must be allowed to touch it unless the engine has been dismantled already. In regard to the main bearings, one must ensure that each of the five caps is labeled to indicate where they are to be inserted in the engine block; if the marks on the con-rods are missing corresponding indentation marks have to be made on the connecting rod caps. The main bearing caps have to be replaced to the previous positions likewise. Loosen the main bearing caps and identify the crankshaft and carefully remove each bearing cap and the bearing together with it and put them on a clean and labeled working platform nearer to the crankshaft block in accordance with the numeration given to the bearings. Next, raise the crankshaft off the engine block being very careful not to cause any harm to the crankshaft. Both halves of the rear main bearing oil seal must be taken out and the main bearings must be pulled out of both the cylinder block and the main bearing caps but they must be kept separated according to their places. The crankshaft gear at the front can be 'unscrewed' by using a particular puller that would give a crankshaft an appearance of being screwed out of the engine block.

Clean the crankshaft with solvent and dry it with compressed air if available. Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks. Rub a penny across each journal several times; if copper rubs off and is embedded in the crankshaft, the journals should be reground. Remove all burrs from the crankshaft oil holes with a stone, file, or scraper to ensure the oil holes are chamfered, preventing sharp edges from gouging or scratching the new bearings. Inspect the rest of the crankshaft for cracks and other damage, and have it magnafluxed to reveal hidden cracks at an automotive machine shop. Measure the diameter of the main and connecting rod journals with a micrometer, comparing the results to the specifications, and check for taper and out-of-round conditions by measuring at several points around each journal's circumference. If the crankshaft journals are damaged, tapered, out-of-round, or worn beyond the specified limits, have the crankshaft reground by an automotive machine shop, ensuring the correct size bearing inserts are used if reconditioned. Examine the oil seal journals at each end of the crankshaft for wear and damage; if grooves, nicks, or scratches are present, the new seal may leak upon reassembly. In some cases, an automotive machine shop may repair the journal by pressing on a thin sleeve, but if repair isn't feasible, a new or different crankshaft should be installed. For a Quad-4 engine, check the oil pump drive gear for wear and damage, and if replacement is necessary, take it to a dealer service department or an automotive machine shop, as the old gear must be drilled and chiseled off while the new gear should be heated in an oven prior to installation. Examine the main and rod bearing inserts.

The crankshaft can only be removed after the engine has been taken out of the vehicle, and after the flywheel or driveplate, crankshaft balancer/vibration damper, timing chain, timing gear, oil pan, oil pump, and piston/connecting rod assemblies have already been detached.

Measure the connecting rod side-clearance with a feeler gauge between the connecting rod caps.

Install the flywheel to facilitate engine rotation during reassembly.

Check the crankshaft endplay with feeler gauges or a dial indicator, ensuring it is correct if the thrust faces are not worn and new bearings are installed.