_shel_ny Posted January 21, 2009 Report Posted January 21, 2009 (edited) ... Edited September 8, 2011 by shel_bizzy_48 Quote
Plymouthy Adams Posted January 21, 2009 Report Posted January 21, 2009 condition of the mains and oil pump clearances is the determining factor for max oil pressure...however the action of the spring is to allow it to by pass and maintain a set pressure... the pressure will vary as the oil get hotter and thins...thus the lower reading at idle...the piston in front of the spring must be able to move freely withing the bore..any sticking may cause excessively high or low, broken spring will read funky also Quote
Merle Coggins Posted January 22, 2009 Report Posted January 22, 2009 Going back to basic hydraulics... a pump creates a flow of oil, the resistance to that flow creates the pressure. The resistance comes from trying to push the oil through the small passages to all of the lubricating points. The pressure relief plunger is there to limit the pressure. If the pressure exceeds the spring tension, the plunger will open up and allow the excess pressure to escape back to the pan. The reason that the oil pressure usually drops when hot is because the oil gets thinner, allowing it to pass through those small lubricating passages easier. When the oil can pass through the passages more freely there is less pressure created. When the engine RPM is higher there is more flow from the pump which causes the pressure to increase as it tries to push all of that oil through the passages. Merle Quote
oldmopar Posted January 22, 2009 Report Posted January 22, 2009 Here is a link that may help with your question http://imperialclub.com/Repair/Lit/Master/015/Page10.htm Quote
John Nickell Posted January 22, 2009 Report Posted January 22, 2009 One page of that pamphlet states "If the plunger stuck closed, the pressure would go high..." So it makes sense that a stiffer spring would cause the oil pressure to rise. Am I right? John Quote
oldmopar Posted January 22, 2009 Report Posted January 22, 2009 They were 3 different spring tensions back when these engines were made not sure if it was to change the pressure or for different vehicles as the engine was used in cars and trucks Quote
Plymouthy Adams Posted January 22, 2009 Report Posted January 22, 2009 yes..stiffer spring..higher reading as it needs more force (oil pressure) to move the piston in the bore..if it sticks open you will have a low reading at all times and some broken springs will give low reading if however it stick when there is no flow it will cause very high pressure as the valve is not allow a by-pass...there are three set springs as I understand for these engines...not recommend to use washers to shim themas some people have been know to do to adjust oil readings... Quote
martybose Posted January 22, 2009 Report Posted January 22, 2009 I believe that with no pluger installed you would have no (or not much) oil pressure, because the oil from the cam gallery would be using the block passages to dump back into the pan. Not a good idea! Marty Quote
Powerhouse Posted January 22, 2009 Report Posted January 22, 2009 I see that a kit(L-425) is available from some known dealers for around $5. I tdoesn't specify spring type. In the manual I have it states the green ones are high compression, the uncolored sprigs are normal duty, and the red ones are lightest. Mine is green...I would like to try a normal spring.... Quote
Fluid drive Posted January 22, 2009 Report Posted January 22, 2009 As some of the contributors have said the plunger and spring do regulate the pressure to a degree. They are there to provide an additional passage back to the oil pan for oil while the engine is cold and the oil is viscos. As the oil warms the spring closes the passage by means of the plunger to whatever degree is necessary to maintain more constant pressure. ( 8 cylinder L heads usually have an adjustable by pass )There are some other factors, however. The L head Chrysler engines circulate oil from the galleys thru the cam bearings and to the mains. As the cam bearings wear oil pressure drops as it will with a worn oil pump. A common practice we used to use to temporarily alleviate low pressure because of worn cam bearings was tto install restrictors or "Thextons" as one manufacturer was named. These go in the galley plugs in the left side of the block and shunt the oil flow to the cam bearings. Cams do not need much pressure as they are more than adequately supplied by splash and the resulting increse in oil to the mains would help for a while. Usually if the bearings are too worn you will wind up with so much spray on the cylinder walls that the rings can't handle it. If any of you have the old gear type oil pumps replace them with a rotor pump. The rotor pumps supply a more consistent volume of oil at higher temperatures. Quote
Powerhouse Posted January 23, 2009 Report Posted January 23, 2009 What do the old gear type oil pumps look like compared to the rotor pump? Part number? Are they for L6? Quote
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