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Macgyver

Onan rods

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Macgyver

I got hold of some new onan rods. They don't have the hole. In the beam or the grove in the crankshaft area with the hole to one side. They are the correct length for a 20 hp. Can they be used?

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onanparts.com
5 minutes ago, Macgyver said:

I got hold of some new onan rods. They don't have the hole. In the beam or the grove in the crankshaft area with the hole to one side. They are the correct length for a 20 hp. Can they be used?

 

The oil hole and the groove, along with the hole in the beam section were eliminated long ago by Onan engineers. New style 18HP & 20HP con rods have casting # 170-4447A, B, C etc.

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Duramax7man7

What was the purpose of getting rid of those two features? Does it cause more oil pressure between the rod journal on the crank and the connecting rod? 

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onanparts.com
On 10/21/2017 at 8:03 PM, Mastiffman said:

What was the purpose of getting rid of those two features? Does it cause more oil pressure between the rod journal on the crank and the connecting rod? 

The oil "spurt" holes were designed to lube the cam above the rods. At some point they figured out enough oil is thrown off the crank/rods to keep the cam happy without the need for those holes. Eliminating both the oil holes/grooves and the hole in the I-beam casting improved the overall strength of the rods. Shot peening the new style rods was/is done to improve the fatigue life of the Aluminum alloy used.

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Duramax7man7

So I was partially correct? ;) Thank you very much for the explanation. I appreciate you! 

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boomers_influence

club

my thoughts here.

it does not matter HOW STRONG the rod is made,

if the owner / operator does not have ENOUHG OIL in the engine

there will be damage when the rod breaks.

 

the stronger the rod, the more damage that is done when it fails due to the lack of oil.

when the forged steel rods and the NEW style aluminum break, the cam and BLOCK are junk many times.

 

thank you. boomer ( the used onan engine parts guy, also NOS and new )

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Duramax7man7

Thanks for the input Boomer. 

SHOT PEENING here is an interesting read on Shot Peening for anyone interested. 

I would hope that operators are checking oil regularly to avoid such a situation.

 I personally think that there would be a slightly better flow of oil around the crank pin to increase wear resistance of the connecting rod along with the shot peening.  

I recently rebuilt a Kawasaki FC420V and ordered a brand new Con-Rod as the old one MIC'd over the max inner diameter on both the large and small ends. It had the oil spurt hole and slot on it. This was on a 1988 Scag walk behind mower. 

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