Re: Engine knock

Posted by HH56 On 2019/1/20 11:08:26

And as for a fix, since the problem of lifter noise does seem to be hit or miss, some having it and some not, finding a reason and "fix" everyone can agree on has been elusive.

Over the years oil flow and the capacity and design of the original oil pump has been the primary suspect starting with Packards own service bulletins. Early in 55 production Packard made changes to the amount of oil going to various places and also issued a kit to lower the amount of oil dispersed to the timing chain so more oil would be available to the lifters. There was a later bulletin that air was getting into the pump so a kit to redirect the relief valve opening into the oil pool below the pump so air could not be drawn in thru the port was designed. It seems neither approach was the "fix". Much later a second design pump was apparently manufactured and put into service as a few have been found when rebuilding engines. The newer pump seems to be few so maybe there was not enough time to get many out or know if it solved the problem. I don't recall seeing anything where someone has completely documented what the differences are between the two pumps to know if Packard had found a definitive issue and designed it out. The overfilling to get the level in the sump higher thus alleviating the noise would tend to go along with the theory of air getting into the pump.

After Packard went away some thought pump bottom plate distortion and vacuum pump wear was the source of air entry. There have been several who offered services to eliminate the vacuum pump section and replace it with a heavy metal bottom plate to support the shaft and provide a non distorting leak proof cover. The Packards International Club was the largest source of the modified bottom cover pumps and for many years that approach was the go to for a "fix". Others thought that since the pumps did not have a proper bushing to support the drive shaft at the top, wear in the cast iron pump body around the shaft and the resulting shaft wobble was the source of air. There were some that offered a service of modifying the pump body to install a new shaft with upper support bushing. If I remember correctly I think there was a person who covered both possibilities by simultaneously doing the bushing and the bottom cover modifications to the pumps. I believe it has been reported that some engines with the PI pump have had intermittent lifter issues too so maybe not the "fix" but it also might be that some or all the other things Packard changed to provide more volume to the lifters had not been done in those engines.

The most recent addition for a "fix" on the pump is a kit to completely eliminate the Packard pump and bolt on an Oldsmobile pump. The Olds pump is modern and easily found, has a robust design for shaft support and comes in standard and high volume versions. The conversion was devised by some posters on this forum and has been available for a few years. So far it seems to have a lot of happy users. Unfortunately it also eliminates the vacuum pump and whether it has completely eliminated the problem is still an open question but results are good to date so we are all hoping it is the final "fix". Of course, the original Packard mods to oil distribution should also be done but the Olds pump does have more volume to spare if some have not been made.