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| Oil pump gear failures -- revisiting the Matrix https://slantsix.org/forum/viewtopic.php?t=38091 |
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| Author: | slantzilla [ Wed Nov 25, 2009 6:10 pm ] |
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Well, the failure itself is the driven gear on the pump Roger. General consensus is the cause of the failure is the drive gear on the cam. My failure was on a gear that had run for many years and miles with a Racer Brown cam. I switched to an MP .528 cam and the resulting failure took less than 1000 miles. It finally died when 2 teeth broke off the pump gear while running 60 mph in traffic on the tollway. I still have the cam down at the shop and could possibly check the casting number if I remember to look. Bill's motor was working on a gear failure at the time it suffered the premature rod bearing wear. It was a Comp X-treme Energy cam that had been in my motor for a couple years. He was using an MP high volume pump, I was not. My motor has a cam button in it, and had one when the MP cam ate the gear. Bill's motor does not. |
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| Author: | Kevin Johnson [ Wed Nov 25, 2009 6:19 pm ] |
| Post subject: | Full stop... |
... please everyone take a few minutes to reread the original technical article and the failure matrix. http://www.slantsix.org/articles/oil-pu ... report.htm http://www.slantsix.org/articles/oil-pu ... esults.jpg |
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| Author: | Rick Covalt [ Wed Nov 25, 2009 6:31 pm ] |
| Post subject: | MP cam |
Ryan's car ate the pump gear in less than 500 miles with no dragstrip runs. It was the MP .528 lift that others have had the same problem with. I'll check and see if I still have it. Rick |
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| Author: | stonethk [ Wed Nov 25, 2009 6:57 pm ] |
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This is a bit out of my league, but I'll throw in my take. The direction of forces driving the pump basically goes: Crank to cam to OP gear to gear shaft to "cloverleaf" pump impeller. So then it would seem that the hydraulic pressure built up in the pump, or rather the oil system, is greater than what the gear can handle and not so much what is going on with the cam gear (there is alot more "meat" behind the cam gear than the pump gear so it makes sense the weakest link would be a small stand alone gear) For instance if someone were to set up a cam and pump on a jig and just run it with no oil going through the pump (but keeping the gears oiled) I would imagine that you could spin the thing all day at whatever rpm and nothing would happen- but put some resistance on the oil pump side via a thick liquid then I see problems arising. Realizing there are more variables than meets the eye, cam walk, etc.- The common thing that stuck out in the matrix that could validate this was >50 psi oil pressure. (thats greater than? Right?) Lower oil psi? Harder gear? Both? Who has done both and had a failure? What is the lowest possible oil psi? Don't mean to be Captain Obvious here, just thinking outloud. |
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| Author: | Kevin Johnson [ Wed Nov 25, 2009 7:14 pm ] |
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| Author: | Charrlie_S [ Thu Nov 26, 2009 6:06 am ] |
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I think we need to keep this discussion going. Whether Kevin is right or wrong does not really matter. It is the presenting of possibilities that does matter. I gather that OP failures are not an everyday occurence. I have never had one, but I do have one engine that had 5 passes on it before it ate a couple of pistons. It has the MP .528 cam and a MP high volume oil pump, both brand new. The motor is still on the stand, as removed from the car. If this discusion can help cure even an occasional OP failure, it will save myself and others, a fair amount of money, to say nothing of time. |
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| Author: | GTS225 [ Thu Nov 26, 2009 7:00 am ] |
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OK....Kevin's input is centering around air entrainment, cavitation, and possible cures to that part of the problem. I'm doing ok at following that part of the equation. I feel the need to ask.......Has anyone dug into the possibility that the gear on the cam was hobbed at an incorrect angle, or perhaps depth? (Could be a contributing factor.) It seems that a large percentage of failures involved MP cams, and as someone said in that other thread, it would only take one guy one day to turn out a big batch of scrap. Roger |
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| Author: | 66aCUDA [ Thu Nov 26, 2009 7:10 am ] |
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Roger Im in agreement with you even pitch angle or ??? As Seymour has suggested, I will see (and post) the blank casting numbers on the cams I have. I believe Doug or ? was given the failed OPG's long ago , however I still have the oil pumps in a box disassembled. Frank |
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| Author: | sandy in BC [ Thu Nov 26, 2009 7:23 am ] |
| Post subject: | |
Quote: Has anyone dug into the possibility that the gear on the cam was hobbed at an incorrect angle, or perhaps depth?
I looked at this pretty hard. My Comp cam gear was compared with 3 stock cams and a new Erson cam . I dont have the facility to properly check angles and depths on gears.....however the quality of the hobbong on the Comp gear seemed sloppy compared to the other cams. The finish was poor enough to get my attention after 2 failures....but not so bad as to be obvious to a casual look.The stock cams gears actually looked better than the Erson as well. I lapped in my Erson with a hardened gear and I used a stone to clean up the outside of the teeth. I am very willing to have my cam and pump gear checked for true. There is no place closer than 7 hours from here that can do this. |
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| Author: | SlantSixDan [ Thu Nov 26, 2009 8:15 am ] |
| Post subject: | |
The matrix looks to me as if we have only North American data points. I wonder if the slant-6 crowd in Australia are having this kind of trouble with their locally-produced cams. Perhaps Cameron and Ray and that lot ought to be pinged and asked. |
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| Author: | sandy in BC [ Thu Nov 26, 2009 9:12 am ] |
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This also looks to be an old problem. My cam was old when it got to me. If maching was a cause (not just a factor) then we would eventually see all the bad gears eliminate themselves. Problem solved? When was the last failure reported? Is this even a current issue? |
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| Author: | slantzilla [ Thu Nov 26, 2009 9:23 am ] |
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I tore apart Bill's motor last summer, so I have seen one in the last year. |
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| Author: | SlantSixDan [ Thu Nov 26, 2009 10:22 am ] |
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Quote: If maching was a cause (not just a factor) then we would eventually see all the bad gears eliminate themselves.
I think that depends on whether the bad machining and/or materials and/or treatment were a transient anomaly or a permanent change. Over in my corner of the auto parts industry, I see deviation from some aspect of the perfectly good specifications, and I see changes made to the specifications usually to cost-reduce the part. The bad parts that don't adhere to the spec are usually limited in number; the problem can be identified and traced and fixed. The bad parts that adhere to slackened specifications are usually here to stay, batch after batch after batch.
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| Author: | Doctor Dodge [ Thu Nov 26, 2009 11:20 am ] |
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| Author: | sandy in BC [ Thu Nov 26, 2009 11:47 am ] |
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Ensure pickup to pump plumbing is not sucking air. |
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