Block engine problem Brisbane -

CRACKED

Blocks crack for similar reasons as cylinder heads do. Like heads, some particular blocks are prone to cracks in certain areas and tend to do so at every overheat. Cracks out of head bolt locations running to the water- jacket are common in many engines. The problem with these cracks is that water can find its way up the cracked thread to the top of the head stud or bolt. Depending upon the position and style of block these cracks can be repaired by the use of a solid thread insert and a few crack repair plugs. The block face must be surfaced ground after this repair. Cracks between cylinders are usually fairly serious and have to be correctly repaired. The crack should be repaired with suitable crack repair plugs close to each cylinder so the sleeve picks up the edge of the crack repair plug. Selection of sleeves should be of a wall thickness that allows the sealing ring of the head gasket to seal directly on the top surface of the sleeves. The sleeves should be fitted into a stepped bore to ensure the sleeve does not move down in service. The block face should be surface ground or milled. Adjacent cylinders to the sleeved bores should be re-honed to remove any ovality created by the interference fit of the sleeves.(.05 to .1 of a MM. or 2 to 4 thousandths of an inch.) A suitable coolant sealer should be introduced to ensure complete sealing during initial warm up. The engine should be driven to normal operating temperature and let cool a couple of times before removing the sealer and adding the correct amount of radiator coolant. Cracks between Welsh plugs are another very common defect that occurs consistently to specific engines. Some manufacturers have design problems that are considered responsible for this failure. The truth is that the blocks are simply made too weak and require extra ribbing in this area. Due to the design of these blocks it is almost impossible to repair these cracks and sustain a 100% seal. They can be repaired successfully but you normally have to be content to suffer a little weeping and staining at the repaired area. The repair procedure is more successful when solid core plugs are introduced so the crack repair plugs can be stitched along the cracks and into the edge of the solid plug. The cracks require the fitting of several cross locks to stabilise the block. The use of straight plugs against tapered plugs appears to be slightly more successful in this repair. Again the introduction of a good quality sealer before inhibitor will give better results.( this repair often suffers staining from inhibitor creep) Cracked bores  are more common in some particular V8 engines than others but all engines can suffer this problem if overheated. These cracks are successfully repaired by sleeving as described in "cracks between cylinders". Cracks to oil galleries are not as common and are usually only minor. A localised cast iron weld will normally fix this problem. The block should be pre heated and allowed to slowly cool. Some peening of the welded area and a pressure test will check the integrity of the repair. Disclaimer Agreement : Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines