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oil pump shaft mod needed removing distributor?


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  • 1 month later...

One of our local members , who is a machinist, was concerned about the effects of having the upper end of the spindle unsupported by the distributor collar. A good point actually. You have a long thin spindle and with the top end of the bushing being unsupported, you are going to get " whipping "  oscillations that will eventually ovalize the bushing in the timing cover at the bottom.  As this bushing gets more ovalized over time, the oscillations will become worse and worse.

 

You could either cut the spindle just above the TC " support bushing"  to minimize the shaft length and oscillation effects, or do what he did and fit a sealed ball bearing that slips over the shaft and locates in the upper dizzy support. You can then put a cover plate over that. There are various ways of doing this.  Minor modifications to the dizzy support are needed and he made a collar to fit over the spindle, but a Lathe is about all you need.

 

It made for a very neat and reliable install. I like the idea that the spindle is fully supported at the top and bottom, just like the factory design. I'll post up a link to his build when I can find it again.  

 

Edit: Took some searching but I finally found the link:

 

http://the510realm.com/viewtopic.php?p=55643#p55643

 

Note: Edited as I forgot to include the wording about the bushing in the Timing Cover. I assumed every one knew that existed. And the bushing in the TC is not adequate to prevent spindle shaft whipping or " whirling ". See post #7 below with engineering link.

Edited by Chickenman
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  • 3 weeks later...

Isn't there a bushing or bearing surface in the front cover?  If there's not then the end of the shaft would wobble around nithe collar at the bottom of the distributor shaft.  Seems like a bit of maybe unnecessary work to cut the oil pulp quill off.

 

Went out and wiggled the distributor drive tang inside the cover on an assembled engine and it seems well-supported.  

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  • 3 weeks later...

You will still get shaft oscillations or " whirling " as engineers call it because of the long thing shaft that is unsupported at the distributor end. It doesn't matter how well supported the shaft is on the oil pump end, or in the timing cover. Without the support at the distributor end you will get oscillations, however slight, and that will eventually elongate the bushing in the Timing cover and then the  oscillations will rapidly get worse and worse until you have a component failure. 

 

The L series oil pump spindle is by no means perfectly balanced because of the offset tang. The article below shows how critical balancing is on long shafts at medium or high speeds.

 

This engineering paper explains the engineering problems associated with high speed shaft " Whirling" :

 

https://www.google.com/search?q=Oscillation+in+high+speed+shafts&ie=utf-8&oe=utf-8

Edited by Chickenman
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I'm trying to find a link to the upper bearing support that our resident Machinist Guru fabricated.

 

In the meantime, here is a link to a rather Famous car in the PNW. " The Bronze" Some wonderful fabrication skills here. Warning 66 pages long and still growing:

 

http://www.the510realm.com/viewtopic.php?f=27&t=530

 

Edit: Finally found the link on the support bearing for the oil pump spindle:

 

http://the510realm.com/viewtopic.php?p=55643#p55643

Edited by Chickenman
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Or, you can just order the oil pump drive spindle and gear assembly for an LD28...

 

 

People take the cranks, but leave so many other useful bits behind!

 

There was an NTN Bearing that slipped down in the hole and over the spindle. Herve Oluette used one on his 73 Z (The Silver L-Engine that was on the Electramotive page for so long, and also the silver Z in the Nissan "Dream Garage" Commercial.) he put a core plug in after packing the top of the cavity "just in case"!

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Edit: Finally found the link on the support bearing for the oil pump spindle:

 

http://the510realm.com/viewtopic.php?p=55643#p55643

Thanks for the link, interesting reading.  The next page after yours has the same question I'm asking.  There doesn't seem to be any supporting (no pun intended) information out there about problems if you don't add a bearing or cut the shaft.  Just "just in case" thoughts.  Nissan went to a plastic locating collar at the end of the distributor shaft with the ZX distributors.  Might be easier to fabricate a Delrin or nylon bushing, than going with a metal bearing and assembly.

 

http://the510realm.com/viewtopic.php?f=3&t=4476&start=30

 

Just wondering.  I haven't seen any reports of failure or wear from those that haven't supported the shaft end.

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