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mike gaines
02-19-2006, 06:43 AM
Just rebuilt a 259 stud v8 for my 1958 silverhawk. Big end bearing failed after 300 miles.Mechanic says the oil release valve failed because the stop end is pitted and allowed oil pressure to stay too high and this caused a lubrication failure. He has suggested resleeving the valve body. Does this sound feasable or should i be investigating elsewhere.Oil pump is fine and has been tested.This is my first step into classic cars and only had eyes for a silverhawk.

N8N
02-19-2006, 07:47 AM
did you have an oil pressure gauge on the car? certainly is possible to ream out the OPRV hole and insert a sleeve, but make sure that that is the problem. I have heard people say that too-high oil pressures can erode bearings but I've driven VW's for years that pull >100 PSI on a cold start and the only one that I've ever replaced bearings on was a Corrado G60 (and that was because VW was using some experimental bearing material on the G60 engines that didn't hold up, fix was to roll in some shells from an earlier engine and problem solved.)

Would be really, really curious to see what your cold start oil pressure was before making any statements as to whether your engine guy's diagnosis is right or not. But if there is pitting in there I would definitely get it sleeved anyway and buy a new OPRV slug just in case. I'd just make 100% sure that you didn't have another problem, like a piece of crap stuck in one of the crank oil passages.

nate

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11SecAvanti
02-19-2006, 09:38 AM
What rod bearing number failed? What is the condition of the remaining rod bearings? How do the mains look? What oil was used for break in? Were the rod big ends resized during rebuild? Was the crank rod journals within specs? Were the rod bearing clearances checked? Were the rod bolts torgue correctly or overstretched? Have heard of extreme oil pressure "washing" out a bearing surface so might be possible but could be other issues too.

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DEEPNHOCK
02-19-2006, 11:53 AM
New cam bearings put in?



quote:Originally posted by mike gaines

Just rebuilt a 259 stud v8 for my 1958 silverhawk. Big end bearing failed after 300 miles.Mechanic says the oil release valve failed because the stop end is pitted and allowed oil pressure to stay too high and this caused a lubrication failure. He has suggested resleeving the valve body. Does this sound feasable or should i be investigating elsewhere.Oil pump is fine and has been tested.This is my first step into classic cars and only had eyes for a silverhawk.

mike gaines
02-20-2006, 01:51 PM
All new bearings installed . Oil pressure between 40 and 80 at start up and then dropped to around 40 for first 150 miles or so and then dropped to around 30 for remainder of mileage untill i heard the failure.All torque settings were within spec ? does this help with diagnosis ?

Mike Van Veghten
02-20-2006, 02:57 PM
How many failures do you have? Just one...all of them?

There is many ways a rod bearing can fail.
1. bolt torque?
2. proper bearing crush within the rod after remachining/torquing?
3. oil supply (low)?
4. bearing clearance?
5. side clearance?
6. rod straight?

As others have said, I've seen oil pressures near 180+psi on race enginges and no bearing problems.

Need some of that good ol forensic eye looking into things.

curt
02-20-2006, 09:18 PM
IS the oil pressure relief valve the valve up by the timing gear?

rockne10
02-20-2006, 09:43 PM
Bottom right front corner of block. It feeds the timing gears.

mike gaines
02-20-2006, 11:20 PM
Thanks for the help , only the 2 mains closest to the front of the block failed. I am fairly sure that the oil typeand quantity were ok as the oil level in the motor after the failure was ok.Have also checked the oil channels for blockage but all clear.If re sleeving the oprv barrel is recommended , anything to look out for?

gordr
02-21-2006, 05:43 AM
quote:Originally posted by mike gaines

Thanks for the help , only the 2 mains closest to the front of the block failed. I am fairly sure that the oil typeand quantity were ok as the oil level in the motor after the failure was ok.Have also checked the oil channels for blockage but all clear.If re sleeving the oprv barrel is recommended , anything to look out for?


Mike, in your first post, you refer to the big ends failing, and in this one you speak of 2 mains failing. Which was it? In the failure-mode charts published by bearing manufacturers, over-pressure damage is usually manifested by the metal being washed off the surface of the shell adjacent to the oil hole. Makes a pattern that looks exactly like water runoff gullies in an arid climate area. I would expect that you would have to have sustained high oil pressure, like enough to peg out the gauge, for that to occur. Without seeing the damaged bearings, I won't venture to speculate on what really caused the damage, other than to say I doubt it was over-pressure. I've seen chatter marks on relief valve plungers before, and they still were working. Are you sure the connecting rods were installed facing the right way?

Gord Richmond, within Weasel range of the Alberta Badlands

11SecAvanti
02-21-2006, 09:20 AM
IMO this does not look like an excessive high oil pressure problem from the relief valve. Sounds more like a poor quality assembly control problem that wiped this motor out. Like the previous post, unless the bearings show evidence of "gulley washout" then the problem is elsewhere. Sorry for your engine lost. One more reason why I do my own repairs.

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