Oil pressure

[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.

[kwkracing]

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!

[skipjobe]

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.

[zipper06]

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.

[kwkracing]

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!!!

[cepx111]

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

[gimmemud]

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.

[dparker]

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.

[skipjobe]

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.

[gimmemud]

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.

[skipjobe]

I have a hurricane to deal with now, the house is surrounded by trees,as soon as this nightmare is over I will start pulling the pan.

[zipper06]

I have a hurricane to deal with now, the house is surrounded by trees,as soon as this nightmare is over I will start pulling the pan.

Where you at skipjobe?, i went thru it last week, i was almost flooded, but survived the bullit. hope you do too.

Zip.

[JimmySmith]

I have had issures with the std melling pump so now I only use a MELLING SELECT Later J. Smith 4621 racing :D

[skipjobe]

I am in Conroe about 30 mile north of Houston.
I tried to speak to Melling today but if I have to change the pump, I will take a look at the Melling select.

[zipper06]

I am in Conroe about 30 mile north of Houston.
I tried to speak to Melling today but if I have to change the pump, I will take a look at the Melling select.

O'h crap, looks like you could be on line for IKE, i hope everything goes o'k for you, as i said i barely dodged the bullit, with flooding and we are still experiencing flooding in some area. Hope you fair better.


Zip.

[skipjobe]

I counted 16 major trees that could fall on the house, The race car has been relocated to a safer location.

[zipper06]

Man i feel for you, I hope you have relocated also. It doesn't look good for your area. I have six 80ft tall pines in my yard and anyone could have fell on the house, but i only had 68 MPH winds, and 12" of water in the yard. I only lost 1 limb about 4" dia and it missed everything and the water liked 1" comming into the house and i have no flood ins. because i'm not in a flood zone.
God luck man and we'll be waiting for an update and hope the best for you and your family.


Zip.

[TheRabbit]

God luck man and we'll be waiting for an update and hope the best for you and your family.
can't imagine what it's like to go through a flood / storm like that. I hope the best for everyone that IKE has reeked havoc upon!

[kwkracing]

did you evacuate? I have been driven my blown rat rod down the highway lookin at all the refugees goin to austin. I live 30 miles east of austin.

[skipjobe]

Thanks for all the kind words. The whole family went different directions. I have a friend nearby that took me and two cars in, he doesn't have any large trees. 2:00 a.M. and the wind and rain are just starting.

[skipjobe]

We got slammed thank the Lord we came out out healthy, I had 8 major trees fall and missed all the buildings. No power and my generator crapped out. Ran great for two days coil failed. back ordered to October. BBQing alot of meat before it spoiles mon by. I guess we will get back on the oil pressure next week or so.

[zipper06]

We got slammed thank the Lord we came out out healthy, I had 8 major trees fall and missed all the buildings. No power and my generator crapped out. Ran great for two days coil failed. back ordered to October. BBQing alot of meat before it spoiles mon by. I guess we will get back on the oil pressure next week or so.

Dude, i've been wondering about you since your last post. i'm glad you and your family made it thru with all in tact and no major damage to your house. I know it may be weeks before all the power is restored, but health and saftey is formost and the other things will fall in line. For me IKE, totally missed me, it went northwest. I just got my yard back in order from Gustof today and that was 2 weeks ago, and donot want to see another in my lifetime.

Zip.

[skipjobe]

We are finally straightened out from the storm, waiting for adjuster. Lots of clean up.
I called Melling today. They think the oil pump is cavitating at higher rpm, they recommended a pump with 10% higher volume part # 10552c with a anti cavitation oil screen that bolts on. I guess I will order one and give it a try.

[skipjobe]

Changed the oil pump on Sunday, I installed the pump that was in the motor before it was rebuilt that worked fine. Set the oil pick up to 3/8 from bottom of pan added a factory filter and still start loosing pressure at somewhere between 5500 and 6000.
I called Melling and they think the pump is cavitating, but this pump did not cavitate in this engine before up to 6800
The only thing I can think of is I had the builder add a torque plate to stiffen up the motor. Any ideas? I am stumped.

[ocalasp76]

On SBC motors there is an oil by-pass port located in the oil filter mount. We always plug this port so we have pressure at high RPM's. Also, we use the Fram HP-4 filter, it's more free flowing. Check out the port hole after removing the filter. Good luck.
---JIM----

[skipjobe]

I put on a moroso pan and removed the oil cooler now we have 80 psi @ 6000 rpm. Thanks

[ocalasp76]

WOW....What could be the blockage in the cooler or its lines?? :shock:
----JIM-----

[outlaw256]

is there any other way besides blockage that could cause oil cooler to be the culprit.i just traded for a car that has a cooler and the oil pressure is about 20 at idle and 40 going down the road. way to low for me but the car dont rattle, knock etc. im planning on freshening her up this winter but i sure would like to drive her for now.anyway i cant think of anything in a coo;er that could cause that but blockage.

[suicidebomb]

If there are any rubber lines going to or from the cooler, and those lines were expanding( ballooning), wouldn't that cause the pressure to drop at the gauge? I don't know, it might not be enough to show that much of a drop. Of course if they are hard lines, this would not apply at all. Just a thought.

[skipjobe]

The oil cooler on this car has water going to the radiator rather than oil. So I suspect it was the pan.

[manley]

Sound's like the problam is solved, But I had a engine that was doing that along time ago! It had a hyd. comp.cam and lifter's in it! I switch to a soild lifter cam and soild lifter and it never did it again!

[radicalz]

The oil cooler on this car has water going to the radiator rather than oil. So I suspect it was the pan.



:D :D Good thing u got it fixed I was thinking that you had done the same thing that i everybody has done in zest to get the engine built and fired to hear it for the first time.....I forgot to check the main and rod clearences on an older BBC....the oil pressure was down after it got warm....should have been signal to me at least, knowing what I know now......but that engine stayed togehter for a couple of years just .010 too much rod bearing clearance....rattled a little bit from time to time but still ran ok :lol: :lol: :lol: ......gooooooooo me!!