| BMora | -- 06-28-2010 @ 12:22 PM |
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My main bearing seized up and marked the crank. The engine is undergoing a rebuild and just wanted to make sure that I wasn't being over or undersold on what should be fixed. Obviously the bearing needs to be replaced and the crank has already been corrected. All gaskets will be replaced. Is there anything else that I need to be aware of?
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| 37RAGTOPMAN | -- 06-28-2010 @ 1:50 PM |
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make sure ALL your oil holes in the cam bearing and main brg's inserts are lined up and have the block boiled out and blow out all the oil holes. and get the LARGER OUTPUT oil pump, and make sure the cranks spins in the block before you install the rod and pistons, try not to overlook anything, hope this helps 37RAGTOPMAN KEEP ON TRUCKIN,,,
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| supereal | -- 06-28-2010 @ 4:21 PM |
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A seized bearing always is due to lack of oil, or insufficient clearance when assembled. It is likely that the oil passages in the crank are filled with sludge and other crud. Have the shop open the crank and hot tank it, followed by probing the passages to loosen any deposits. The openings should then be tapped and fitted with plugs when done. We did an 8CM Merc crank last year that was almost completely plugged. Inspect all old cranks to see if they are clear. We then check the balance to be sure it is within tolerance.
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| FrankM-RG5 | -- 06-28-2010 @ 4:54 PM |
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make sure that I wasn't being over or undersold on what should be fixed. You really need to give us more info. Was this a fairly fresh rebuild that failed or a high mileage engine that finally gave up the ghost? Or maybe it jusy got over revved. As others have said you need to make sure all passaes are clear both in the block and the crank. Sometimes when you get into things enough you get a "while I am here" approach to freshening up things like valves and rings.
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| BMora | -- 06-28-2010 @ 5:47 PM |
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More Info: Oil starvation is suspected due to 60 years of sludge build up. Engine low mileage (7,500 miles) Never rebuilt, only 2 valve springs replaced. Block has been tanked (cleaned) and primed, no cracks detected, will be pressure tested. #2 cylinder has pitting so a re-boring/honing of all the cylinders has been prescribed. All pistons and rings to be replaced (few cracked rings found along with normal flathead cracks in the sides of pistons). Valves to be replaced with adjustable valves for sake of rebuilding process ease; nobody wants to file away anymore (have heard that some of these are too soft and could be problematic?) Everything else better than expected by shop, due to low mileage.
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| supereal | -- 06-29-2010 @ 3:46 PM |
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Did read that right, only 7,500 miles in 60 years? I have seen that before only in old fire trucks. The worst thing to do to an engine is to seldom drive it. We try not to start any vehicle unless it can be driven at least ten miles. This burns off the moisture in the oil pan and exhaust system. Given that many old engines used non-detergent oil, and often sat for long periods, it is a wonder any of them survived. It is a tribute to the early engineers who designed them to be overbuilt. It certainly isn't that way today.
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| BMora | -- 06-29-2010 @ 4:25 PM |
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You read that right, and you are correct, it is a fire truck.
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| TomO | -- 06-29-2010 @ 6:00 PM |
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You should have all valve springs replaced while the engine is being rebuilt. I would go with the 80 lb oil pump,a new pressure relief valve and a new oil pressure sender. The cam bearings should also be replaced after hot tanking an engine. Low mileage on a fire engine does not always mean that there are low hours on the motor. Fire engines are driven short distances to a fire, but then the engine either idles while the fire is extinguished or runs a pump to pump water. Tom
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| 37RAGTOPMAN | -- 06-30-2010 @ 6:15 AM |
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If the engine is hot tanked, replace the bearing like TOM O said the hot tanking eats the bearing and desolves them, if left in there overnight for sure, AWAYS replace the CAM BEARING when you have the engine apart,this is were you loose oil pressure if worn, 37RAGTOPMAN KEEP ON TRUCKIN,,, ANY AUTO MACHINE shop has the SPEACIAL TOOLS if not LEAVE
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| BMora | -- 06-30-2010 @ 11:51 AM |
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Does the oil pump and line flow to the cam shaft and keep it flooded with oil at 40lbs of pressure? I thought that the oil pump pumped it front he pan to the filter and then back into the pan?
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| supereal | -- 06-30-2010 @ 12:43 PM |
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In the old style filter, only part of the pump output was sent to the filter, which drained back into the oil pan. There is a restricter in that line to prevent starving the oil system and maintain pressure. The balance of the flow goes to the relief valve at the front of the valve gallery, then on to the cam bearings. In the more modern "full flow" system, all the oil from the pump goes to the filter. In the event that filter clogs, there is a bypass valve built into the filter.
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