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Old Girl 1978 Roper


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#496 devans OFFLINE  

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Posted April 08, 2015 - 01:20 PM

I just finished reading this whole thread and I've got to say you do some real fine work. 


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#497 larrybl ONLINE  

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Posted April 08, 2015 - 02:28 PM

Pistons are comming back out tonight :wallbanging: . No old parts are to be used. Oil rings are the new style.


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#498 KennyP ONLINE  

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Posted April 08, 2015 - 04:00 PM

Get a pic of these 'NEW' style rings, please.


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#499 larrybl ONLINE  

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Posted April 08, 2015 - 06:41 PM

Here you go Kenny, I took these before I installed the rings. Meant to post the question before I installed them, but followed the manual instead.

Attached Thumbnails

  • New Stile.JPG
  • Old stile.JPG
  • P1120467.JPG


#500 KennyP ONLINE  

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Posted April 08, 2015 - 07:02 PM

Is the first pic the original rings? Kinda looks like most oil rings I've seen.



#501 larrybl ONLINE  

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Posted April 08, 2015 - 08:09 PM

Is the first pic the original rings? Kinda looks like most oil rings I've seen.

1st picture are the "new" oil ring, second is the old oil ring. I told onanparts about my thread over here, hope he visits and helps us out with his wealth of information.


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#502 larrybl ONLINE  

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Posted April 08, 2015 - 08:12 PM

I removed the offending old ring and re-installed the pistons, they went in easier but I still needed the band clamp. Cheep ring compressor is from Autozone $17.99.

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  • P1120615.JPG

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#503 larrybl ONLINE  

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Posted April 08, 2015 - 08:16 PM

From Onanparts.

No old parts are reused at all.

Single oil ring with expander is old school. Three piece oil rings are new school.
Expander and two oil rail rings. Critical that the rings are installed correctly though.

Oil expander end gaps must meet and not overlap. Rail ring gaps should be
installed so they are not close to each other. All three gaps need to be
in different locations around the piston, staggered etc. Same as the
compression rings, staggered so gaps are not lined up.

Side note: Next crank gear install you can just heat it up for a minute or
two with a small propane Bernz A Matic style torch. I heat all around the
ID of gear then drop it right on the crank. No force needed etc.

Do not overheat the gear. Special tool required here...Spit! Yes, spit on the gear every 10-15 seconds after the first minute until the spit balls up and rolls off. smile.gif

If the gear is overheated and turns blue it's possible the hardness will be affected and soft teeth wear quickly. Just keep spitting! smile.gif

Although you are past most of what's covered this MTF sticky might be helpful in the future.
How to rebuild your Onan engine 


Your method works too for the gears but no Baby Back Ribs at the same time?? smile.gif


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#504 KennyP ONLINE  

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Posted April 08, 2015 - 11:40 PM

That first pics (of the rings) is a typical small block Chevy oil ring set. Put in many sets of these.



#505 MH81 ONLINE  

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Posted April 09, 2015 - 06:08 AM

I wonder if there is a specific reason why the change? Did the old ones not reform correctly?
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#506 Onanparts OFFLINE  

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Posted April 09, 2015 - 11:03 AM

I wonder if there is a specific reason why the change? Did the old ones not reform correctly?

Three piece oil rings offer improved oil control over one piece and were adopted by the automotive industry long ago. Small engine manufacturers caught up a little later on.

 

Larry: Good catch! Leaving the old style expander in would have caused problems.....and you would be doing lots of this... :wallbanging:


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#507 Onanparts OFFLINE  

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Posted April 09, 2015 - 01:07 PM

Larry, If your timing/gear cover is still removed double check that the really small ball bearing that supports the bottom of the governor shaft did not fall out during cleaning or disassembly. 3/16 is the size. Easy to miss it. Early covers had a needle type bearing, later all have the ball bearing. Yours should be the later style bearing.


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#508 larrybl ONLINE  

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Posted April 09, 2015 - 01:19 PM

Thanks! I saw that in the manual, and made sure the ball was put back in before I installed the shaft. Should I do anything with the oil pressure releaf? I have not removed that bolt to check the spring and valve.



#509 Onanparts OFFLINE  

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Posted April 09, 2015 - 02:17 PM

Thanks! I saw that in the manual, and made sure the ball was put back in before I installed the shaft. Should I do anything with the oil pressure releaf? I have not removed that bolt to check the spring and valve.

I would remove and inspect them. They should be OK but it only costs a few minutes to make sure. Make a note of how they come out.

 

Just found this from my rebuild write up....

 

The oil bypass valve and spring are what regulates the oil pressure. The bolt in the first pic is removed and the spring will typically fall out after you turn the block upside down. Sometimes the bypass valve will come out with it, sometimes not.

If not use a small magnetic pickup tool or spray some carb cleaner down the hole to breakup the oil that is holding it in place. If using compressed air to launch it out of the block and you don't put a rag over the opening to catch it and hours later it's still hiding someplace you will never find it.....Part number is 120-0398.

The valves hold up well but it's always a good idea to replace the spring, part number 120-0140 when rebuilding.

When putting it back in the "flat" end goes in first. The smaller rounded end on the top is what keeps the spring centered. Oil up the valve before installing it, drop it in the hole and then put the spring in. The copper washer can be reused if annealed. Heat it up cherry red and drop it into some water.

What? You lost the bolt too? It's a 3/8-24 X 7/8. The length is what sets the oil pressure. Torque it to 10 foot pounds. Don't over tighten or you risk cracking the block!

Attached Thumbnails

  • bypasspic.jpg
  • bypasspic1a.jpg
  • bypasspic2.jpg
  • bypasspic3.jpg

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#510 larrybl ONLINE  

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Posted April 09, 2015 - 03:03 PM

Spring has been ordered.






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