[steveo]

due to some.. um.. fuel injection errors while repairing my car, my crankcase was filled with fuel, and some carbon. i strained the fuel i pulled out and sliced the filter, and it contained no metal.

i drained the fuel/oil mix out, put in fresh oil with some ATF, ran it to temperature, and drained it again. the oil is now golden and perfect.

this is a recently refreshed engine, rings, bearings, etc. engine runs well; no weird knocks or anything. the compression is good..

the oil pressure, at idle, is perfect. i've had a bunch of LT1s. the gauge reads 1/3rd at cold idle, drops to just above 1/4 at hot idle.

weird thing is, no amount of rpm will increase that oil pressure. whatever the oil pressure is at idle, it's still there at 4000 rpm. it doesnt drop, it doesnt fluctuate... its just.. there.

i put a mechanical gauge on it twice. the first time, i blipped the throttle, and pressure went up, so i figured.. ok, it's the sender. drove around for a bit.

i just bought a sender, but because they're such a bitch to put in, i figured i'd put the mechanical gauge on it again.. and i blipped the throttle, nothing

the oil pressure stays 100% constant at all rpms

what would cause something like this? bypass stuck open maybe? how does an oil pump bypass work?

 

[steveo]

i was thinking a few washed out bearings, but i've destroyed several bearings before, so i know how they behave... they had shit oil pressure at idle, and it always climbed with rpm at least a little bit..

 

[cocobolo95]

Did the low oil pressure start when the fuel problem occurred, or has it been there since you refreshed the engine?

When you refreshed the engine, did you take out any oil galley plugs?

 

[steveo]

i didnt do the rebuild myself

that was my first thought too, a plug got left out or something, but that would give really bad oil pressure at idle too, wouldn't it

the block was tanked, so everything came out

 

[USMC]

Did it do this before the fuel issue? Reason I ask is because the fuel could have washed out the oil pump and now its not working well due to initial suction. Typically an oil pump ill have to be pack with grease ( I use Vaseline) to create that initial suction to work properly. This said I have also had the same issue and never had a problem with my oil pump afterwards. Is this a Melling HV oil pump?

 

[steveo]

i have no idea what pump is in it. since the rest of the bottom end is stock, i'll make an assumption there.

i honestly have no idea if it had good oil pressure before it was washed. i honestly never payed attention to that while i was testing stuff

the fuel in oil thing wasnt THAT bad, and it wasn't run very long like that, and never put under load.

i've had a cooked oil pump before too, and it always had low pressure at idle too. that's the weird thing. the idle oil pressure is perfect. totally stable. but you can floor it, and the oil pressure barely twitches.

 

[steveo]

every single oil system failure i've had on an SBC or an lt1, it still responds to rpm somewhat, and it shows up at idle too.

i know im going to end up at least pulling the pan, but i want some theories first.. hell i'll redo the bearings again if i have to, but it sure isn't behaving like a cooked bearing..

i've honestly never played with oil pumps before; i've always just bought them, thrown them in oil overnight, bolted them up..

i have two questions, and this is just out of interest, even if unrelated to my problem:

1. how does the oil pressure relief/regulator/whatever for the pump work?

2. where do the two oil pressure ports actually fit into the oil flow?

 

[ShowNoMercy]

Pretty nice article on SBC oiling.

GrumpysPerformance.com • View topic - oil system basics

Sit back, and read for days :lol:

The spring in the pump just allows higher pressure oil to bleed back to the pan AFAIK, so pretty sure none of that could have been hurt by a gas mix.



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[steveo]

im not convinced the fuel in the oil is even related, as i said, i never saw the high rpm oil pressure before, as it wouldn't rev. lets assume it started out like this, for the time being..

 

[steveo]

thanks for the link by the way that's a really good collection

so theoretically a partially stuck open, broken, or weakened spring/whatever in the pump could still allow healthy oil pressure at idle, but any attempt to gain higher pressure through rpm could flunk?

its so weird that it doesnt climb at all with rpm.

 

[ShowNoMercy]

Yea you would make as much pressure as you could with an open bypass essentially, but I would assume it would still vary pressure wise, as more flow would bleed off more.



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[steveo]

any more ideas before i have to go and pull the engine?

 

[ShowNoMercy]

I would be leaning towards it was a problem before the gas issue.

If you got the gas out and it has fresh oil in there without any contaminants, then, you may have trashed something before and are just noticing it now.

Another last thought though, the gasket between block and oil pump, maybe gas ate it away (long shot) and its spewing oil out back into the pan? Thats the only paper gasket I can think of that would affect pressure.



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[cocobolo95]

Long shot here, but maybe pick up tube has partially disengaged from pump body and your sucking some air into the pump, along with the oil.

 

[steveo]

i suppose that's possible, but what freaks me out, the oil pressure is so incredibly stable. it's sure not acting like it has any air in it

i'll try to add an extra quart just to check.. but everyone tells me the bottom of the pump is submerged at idle anyway

 

[steveo]

Another last thought though, the gasket between block and oil pump, maybe gas ate it away (long shot) and its spewing oil out back into the pan? Thats the only paper gasket I can think of that would affect pressure.

i thought about that one too, but you'd figure if you floored it, oil pressure would still go up a bit.. and idle oil pressure would suffer

im leaning towards the pump being screwed up in some way.. i guess i could drop the pan, it's half as hard as just pulling the motor though!