04-08-2017, 06:09 PM | #1 |
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Join Date: Jul 2010
Posts: 136
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Oil pump shaft
I did a mild rebuild on my 8ba. Nothing too in depth as the engine looked in excellent shape. I also installed a new Melling m15 high volume oil pump. The engine has been run for 2 hours and showed good oil pressure, 20 at idle, 50 at 2000 rpm. During tuning the oil pressure dropped to zero. I shut it off and did problem diagnosis which showed nothing coming in to main oil gallery. I dropped the pan and removed the oil pump only to find the shaft had snapped about 2 inches up from the drive gear. The shaft was not twisted, the gears looked good and there was no sign of a jam in the housing. I am an engineer but not a metalergist so to my eye the break looked clean and somewhat concave at the break. I am putting it down to a flaw in the metal itself. I would think the drive gear pin would fail first if there was in fact a jam. Anyone had this happen??? Thanks...Doug
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04-08-2017, 06:32 PM | #2 |
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Join Date: May 2015
Posts: 8,119
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Re: Oil pump shaft
It's probably good that it failed. If yours is a 'street engine' the high volume Melling 15 oil pump is overkill and can cause problems with excessive oil pressure. The Melling 19 is more than adequate for a street engine. The M15 is usually used in race engines....
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04-08-2017, 06:48 PM | #3 |
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Location: Buchanan, MI
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Re: Oil pump shaft
Is your M15 pump a real Melling or Mac's/ Drakes/Speedway wantabe ?
I use M15 pumps in all of my flatheads, stock & modified with no ill effects. Last edited by 42merc; 04-08-2017 at 07:18 PM. |
04-08-2017, 08:19 PM | #4 |
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Join Date: Jul 2010
Posts: 136
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Re: Oil pump shaft
The pump is a genuine melling stamped M15. I have had it a while but it is new. This sheered off drive shaft is a mystery. I see no other reason than metal failure.
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04-08-2017, 09:07 PM | #5 |
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Join Date: Oct 2011
Location: Gloucester VA
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Re: Oil pump shaft
Spitballing here. Something was drilled off-center to cause the shaft to wobble. Drive gear or idler.
Lonnie |
04-08-2017, 09:32 PM | #6 |
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Re: Oil pump shaft
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R |
04-09-2017, 03:40 AM | #7 |
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Join Date: May 2010
Location: Fitzgerald, Georgia
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Re: Oil pump shaft
This is a very unusual situation. I have never seen it happen with the large driveshaft diameter of our Flatheads. I have seen several instances on the newer V-8 Fords which use the tiny hexagon drive, from the distributor, but the Flathead shaft is 1/2" diameter(as I recall) and it seems like the lowest level of hot rolled steel could easily withstand the stress. I would chalk this one up to a defect in the shaft if no other evidence is there. However, I agree with Ronnie about a call to the manufacturer. They SHOULD want to look it over and, perhaps, provide a replacement.
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04-09-2017, 08:44 AM | #8 |
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Join Date: May 2010
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Re: Oil pump shaft
Here is a shaft from a ford small block that has failed.(looks like a barber pole)Most of these were from foreign objects jamming the pump.Not uncommon in those applications.
JWL is correct about the shaft in an 8ba being unusual. R |
04-09-2017, 09:21 AM | #9 |
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Location: Chester Vt
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Re: Oil pump shaft
Never use Mellings "STUFF"
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