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Strange oil pressure problem
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DRR Trophy
posted
Hello All
I have a strange oil pressure problem. First I must tell you this is a 327/295 SS combo, that came in a car that I bought. The Motor was originally done by Jeff Stealey. The only thing I changed on the motor was the oil pan. The Oil used is 10/30 Brad Penn.

When the motor was started up it had 55 to 60 LBS oil pressure.
Once the motor reached operating temp around 170 degrees, the oil pressure started dropping down to 20/25 LBS of pressure. even if you rev it up, it would only go up about 5 LBS then fall right back down. (this happened while the motor was idling at 1300 RPM)

Cutting the motor off for a few minutes and starting it back up, the oil pressure would again be at 55 to 60 LBS. Once it would run for a few minutes it would drop down again to 20/25 LBS.

I say ok need to replace the oil pump, so that what we did. Guess what it did the same exact thing.
Slightly confused, any ideas?
Would it help if I put 20/50 oil in it?
O yea it never totally lost oil pressure.

Thanks for any ideas or explaintion
Cal
 
Posts: 46 | Location: Southern MD | Registered: November 21, 2009Reply With QuoteReport This Post
DRR Pro
Picture of rusty
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oil pan to close to suction ?
too much clearance on bearings(my personal favorite)


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

 
Posts: 1390 | Location: texas | Registered: February 17, 2006Reply With QuoteReport This Post
DRR Trophy
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quote:
Originally posted by rusty:
oil pan to close to suction ?
too much clearance on bearings(my personal favorite)


Pick up is 1/4" off bottom of pan.
Bearing clearance was a thought to. But as I said it was a running motor when I bought the car. So without taking it apart can't answer that question.
Thanks for your thoughts.
Cal SST 1177
 
Posts: 46 | Location: Southern MD | Registered: November 21, 2009Reply With QuoteReport This Post
DRR Sportsman
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Change the Convertor Laughing Hard
 
Posts: 654 | Location: Here | Registered: November 15, 2012Reply With QuoteReport This Post
DRR Elite
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Seems like it is losing volume somewhere after warming up. Didn't change cam/lifters? My first instinct would be the bearing clearances. Maybe lifter clearances? You can check bearings roughly with the pan off. I wouldn't think a weak bypass spring would act this way.


Foxtrot Juliet Bravo
 
Posts: 6362 | Location: Illinois | Registered: July 08, 2004Reply With QuoteReport This Post
DRR Trophy
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I don't think 1/4 is enough clearance 3/8 to 1/2 is the norm.
 
Posts: 39 | Location: ohio | Registered: August 15, 2009Reply With QuoteReport This Post
DRR Trophy
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is putting the original pan and pickup back on an option? If it is I would start there to see what that does
 
Posts: 39 | Location: ohio | Registered: August 15, 2009Reply With QuoteReport This Post



DRR Pro
Picture of TORQIN
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Drain oil and see (measure) how much actually comes out...could it be low on oil?
 
Posts: 1749 | Location: Houston, Tx. | Registered: November 27, 2008Reply With QuoteReport This Post
DRR S/Pro
Picture of Big Steve
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If it was fine before you changed the pan then thats your answer, there is somthing up with that pan you installed starving the pump
 
Posts: 2403 | Location: Moving back to the door side | Registered: April 30, 2010Reply With QuoteReport This Post
DRR Top Comp
Picture of wideopen231
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Didn't do count but add one for clearance.My panel has 454 I built for grandfather and it sat 15 years before I put it on road after he passed.He may have had 3000 miles on it. Crabk it pegs 60 lbs gauge drive it let everything get heat soaked and idle pressure drop to 35 to 45 lbs(nothing to worry about) the drop does get your attention.

I wonder about it and worried a little then remember guy at maching shop has done my work for close to 30 years.90% of motors I was building or me and always on high side of clearnaces,I spin the hell out of my toys.Maybe why I loved the eliminator class that left line at 12000 plus. Figure John just naturally set clearance to high side and I never thought a thing abot it when checked them.

Heck its is sbc and 327's love rpm so little loose is good,we are talking motors not women right.




America home of free. Brought to you by 2nd amendment.
 
Posts: 4169 | Location: Greensboro NC | Registered: May 24, 2011Reply With QuoteReport This Post
DRR Pro
Picture of rusty
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i remember having this issue years ago and a old mechanic told me it was bearing clearance.he said pull the pump put air pressure on the hole in the block where the pump flow goes out,then watch the crank and see where the most oil comes from.i did and and it was very obvious that the rods were too loose.if you swap pans back that is fairly easy to do in the process


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

 
Posts: 1390 | Location: texas | Registered: February 17, 2006Reply With QuoteReport This Post
DRR Pro
Picture of CURTIS REED
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This may sound dumb but could the heat be causing the flat part of the oil pan to bow up some giving you less clearance to the pick up? You could check it with a straight edge before and after to verify.

You say it was a running engine but you didn’t say whether you ran it before and it didn’t do this. We assume it didn’t by your post.



____________________________
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Posts: 2912 | Location: KIEFER, OK. | Registered: August 17, 2007Reply With QuoteReport This Post
DRR Sportsman
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I think you put the original pan back on. If problem is solved then you know the pan you installed is the cause. If swapping pan doesn't fix it then it has to be a problem with internal clearances somewhere since you have already changed pump.
 
Posts: 486 | Location: Going to or returning from the chipmine. | Registered: July 01, 2011Reply With QuoteReport This Post
DRR Trophy
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Good morning
Changing the pan back is not an option in this car.
I did hear the motor run, but never ran the motor down the track. Being a SS 9000 plus RPM SBC I would think the clearances would be a little loose. I was just hoping this motor could get me threw a couple races so I could save a little money to replace the broken short block.

O well guess it is just my luck
Cal SST 1177
 
Posts: 46 | Location: Southern MD | Registered: November 21, 2009Reply With QuoteReport This Post



DRR S/Pro
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I agree that 1/4 inch of clearance between the pick up and the pan is not enough. I set the pick up at 3/8 with a steel pan. Since the only change was the pan that is more than likely the problem.

I assume the change was due to a pan/chassis clearance issue, if not re-install the old pan and see if that corrects the problem. Losing that .125 of clearance is probably the cause of your pressure loss.

Bob
 
Posts: 3074 | Location: Lakeside, Ca | Registered: February 15, 2003Reply With QuoteReport This Post
DRR Sportsman
Picture of sr4440
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aside from what everybody else has said, I would look for a crack in the pickup tube. It would open up when hot and quickly cool off and close back up, giving you the symptoms you described.


Joe


Without data, you’re just another guy with an opinion.
 
Posts: 1297 | Location: TEXAS | Registered: February 07, 2003Reply With QuoteReport This Post
DRR Trophy
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[QUOTE]Originally posted by Cal of MD



Cutting the motor off for a few minutes and starting it back up, the oil pressure would again be at 55 to 60 LBS. Once it would run for a few minutes it would drop down again to 20/25 LBS.

If you had a clearance problem,cutting the motor off for a few minutes would not mysteriously give your clearance back.Sounds like something is being sucked into passage way when started and released and resettle when switched off.Could be something as simple as something being sucked into the oil pressure line/gauge.....And didn't see a mention of checking oil filter...
 
Posts: 262 | Location: Fayetteville | Registered: May 05, 2003Reply With QuoteReport This Post
DRR Pro
Picture of rusty
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quote:
If you had a clearance problem,cutting the motor off for a few minutes would not mysteriously give your clearance back.Sounds like something is being sucked into passage way when started and released and resettle when switched off.Could be something as simple as something being sucked into the oil pressure line/gauge.....And didn't see a mention of checking oil filter...

good thought


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

 
Posts: 1390 | Location: texas | Registered: February 17, 2006Reply With QuoteReport This Post
DRR Sportsman
Picture of sr4440
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Just to make sure, you did change your oil filter since the problem started.

Joe


Without data, you’re just another guy with an opinion.
 
Posts: 1297 | Location: TEXAS | Registered: February 07, 2003Reply With QuoteReport This Post
DRR Trophy
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Good morning all.
Didn't think about checking the oil pressure line.
but I will later today. As far as the oil filter, yes it has been changed twice.
Both filters were Wix Filters.
Thanks again
Cal
 
Posts: 46 | Location: Southern MD | Registered: November 21, 2009Reply With QuoteReport This Post
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