O-300 Crankcase Cover Plug

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bjoness
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O-300 Crankcase Cover Plug

Post by bjoness »

The O-300 parts manual (figure 9 index 35) shows a pipe plug installed in the crankcase cover under the starter, between the mags, and above the tachometer cable adapter. My cover (early style as shown in the figure) does not have a plug installed or a hole where a plug could be installed. Does anyone know if any early crankcase covers had just a plug. Also, what was the purpose of the hole that the plug was filling? It almost looks like a plug that could have been removed to prime the oil pump.
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cessna170bdriver
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Re: O-300 Crankcase Cover Plug

Post by cessna170bdriver »

Later engines had a right angle starter drive and a pad for a "wet" vacuum pump. That plug was replaced with a pipe to hose adapter for the vapor return from the pump. If you check your parts book closely you'll probably notice a different part number for the accessory case assemblies for the later engines.

The oil system can be primed through the front of the crankcase. There are plugs in the front of each oil gallery.
Miles

“I envy no man that knows more than myself, but pity them that know less.”
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GAHorn
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Re: O-300 Crankcase Cover Plug

Post by GAHorn »

When reinstalling such plugs, remember that tighter is not better.
Don't try to crack the case!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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