Oil pressure

Old 09-09-2008, 12:11 PM
  #1  
skipjobe
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Default Oil pressure

Forged 383 LT1
Got the engine in, working on tuning, on full throttle pull loosing oil pressure. test in neutral with engine warm. 1000 40 psi 2000 40 + 3000 40+ 4000 psi drops like a rock, back to idle, pressure comes right back up.wix filter sae 30 motor oil 6 quarts. [over filled]
Changed to a cheap purilator filter new 10w30 oil 6 quarts 1000 ok 2000 ok 3000 ok 4000 ok. in neutral. road test good to 5000 drops like rock between 5000 and 6000. checked for missing oil pick up it is in place about 1/2 inch off bottom of pan viewed through drain hole it is not loose and it was welded. Stock pan, Melling 55A pump.
I am stumped, I feel like the pump in going dry or sucking air, it is a real pain to pull the pan at this point so I want to exhaust all other options before I start pulling it apart, and at this point I don't know what I am looking for. The engine was built by a local dirt track engine builder he is also stumped.
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Old 09-09-2008, 01:04 PM
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kwkracing
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a few years ago i recieved a engine that did the same thing, great oil pressure at idle and mid, but as soon as you stab it the oil pressure dropped, let it idle and the pressure came back. Tore it apart and what had happened was the builder put .020 rod bearings on a .010 rod journal..... funny huh? Cleaned it and put the right rod bearings in it and it was fixed. Hopefully this is not your problem!
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Old 09-09-2008, 01:38 PM
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skipjobe
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I provided the engine parts crank rods bearings but I didn't check anything, I believe the builder is competent, I will check the bearings if I have to pull the pan, I am not looking forward to that operation, I can get the pat without removing the engine but squeezing the pan back in without it leaking oil will be a good challenge. Thanks for the idea.
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Old 09-09-2008, 02:20 PM
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zipper06
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I saw this happen once when the oil pickup was too close to the bottom of the pan. It can happen if you have an after market pan or pump pickup. Just a thought.


Zip.
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Old 09-09-2008, 03:00 PM
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kwkracing
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same thing ...bought everything and took to a highly known engine builder....... For some reason he didnt check it or the crank got swapped or something? it had srp piston, air flow heads....Everything new but the crank. The builder quickly fixed the problem!!!
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Old 09-09-2008, 07:54 PM
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cepx111
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You can bank on having to take the engine out and pulling the pan There's just no other way to determine what is going on without doing this.
You can look, stare, and think a oiling problem to death but in the long run you'll be taking the engine out and doing some exploratory surgery, so go ahead while the weather is mild and make plans to do this.

Oil pump pick-up to pan clearance is my first thought. Its possible that its too close>
1/4 MIN - 3/8 INCH MAX
Did the builder go crazy with the silicon? If so the pick itself could be partially stopped up with that junk.
Proper rod and main bearings and clearances, alittle plastigauge goes along way here, like previously mentioned - one wrong size bearing insert can make a big difference and doing a simple plastigauge check on the clearances would have spotted this.
This sounds dumb but is often overlooked, the oil pump cover bolts can sometimes loosen themselves up, never assume they are tight from the manufacturer ( ask me how I know>?) Now I always take them out spray them off with some loctite primer and red
loctite them in place.
Good-luck man>
I hope you get your motor fixed, Charles
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Old 09-10-2008, 05:19 AM
  #7  
gimmemud
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I had a BBC do that exact thing a few years back, I noticed it as I was warming it up before a race. The pressure was good until it got around 4000 rpm and it would drop to nothing. I was young and stupid and thought it was just a bad gauge or sending unit and ran it like that for 2 passes. When I removed the pan, the pickup was laying in the bottom, broke off. Thank God for Mobil One synthetic oil, didnt hurt anything luckily.
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Old 09-10-2008, 07:08 AM
  #8  
dparker
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Default Re: Oil pressure

Originally Posted by skipjobe
Forged 383 LT1
Got the engine in, working on tuning, on full throttle pull loosing oil pressure. test in neutral with engine warm. 1000 40 psi 2000 40 + 3000 40+ 4000 psi drops like a rock, back to idle, pressure comes right back up.wix filter sae 30 motor oil 6 quarts. [over filled]
Changed to a cheap purilator filter new 10w30 oil 6 quarts 1000 ok 2000 ok 3000 ok 4000 ok. in neutral. road test good to 5000 drops like rock between 5000 and 6000. checked for missing oil pick up it is in place about 1/2 inch off bottom of pan viewed through drain hole it is not loose and it was welded. Stock pan, Melling 55A pump.
I am stumped, I feel like the pump in going dry or sucking air, it is a real pain to pull the pan at this point so I want to exhaust all other options before I start pulling it apart, and at this point I don't know what I am looking for. The engine was built by a local dirt track engine builder he is also stumped.
You could be pumping your oil up to the valve covers. Did you put oil restrictors in your block. These will restrict oil to the lifters which will keep you from pumping all your oil up top. I once installed a roller cam in a 351 clev. and it would pump the pan dry inless than 2 minutes. I ended up installing a Jack Rouse restrictor kit in the main journals of the block to fix. I think that maybe your problem. Let me know what you find.
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Old 09-10-2008, 01:25 PM
  #9  
skipjobe
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Default oil pressure

I suspected that it was pumping the pan dry the reason I added another quart of oil, I have read that if a high volume pump is used without a after market pan it will have that effect.
No restrictors were installed because the car will see a little street time.
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Old 09-10-2008, 05:29 PM
  #10  
gimmemud
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You are not pumping the pan dry @4000 rpm, that will only happen @ high rpm's unless you have a serious drainback blockage.

You are gonna have to remove the pan to find this problem, it is ( as someone has already mentioned) pick up too close to bottom of pan or pickup is loose most likely. If not you have serious bearing clearance problems.
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