Fresh big block with low oil pressure at idle.

[Irishman999]

Anyone know how a oil pressure gauge in a 90 is constructed? Is there something mechanical that could be worn out causing like a dead spot in the gauge?

It hits a point about 20 psi where it just drops to zero, it did the same thing with the old engine and I drove it around like that with plenty of idling for months without engine noise or anything. The guy that got my last engine even said the rotating assembly looked brand new.

New engine has a ton of oil pressure when you blip the throttle, its just when it idles the gauge goes lower and drops to zero.

I ordered a new gauge from LMC.

 

[chevyk10]

I would probably try another gauge as well. Mechanical of coarse


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[HotRodPC]

Anyone know how a oil pressure gauge in a 90 is constructed? Is there something mechanical that could be worn out causing like a dead spot in the gauge?

It hits a point about 20 psi where it just drops to zero, it did the same thing with the old engine and I drove it around like that with plenty of idling for months without engine noise or anything. The guy that got my last engine even said the rotating assembly looked brand new.

New engine has a ton of oil pressure when you blip the throttle, its just when it idles the gauge goes lower and drops to zero.

I ordered a new gauge from LMC.

It could even be in the gauge sender Dawg. And you mention it did the same thing with the old motor? So that's a good thing really. Honestly, I don't trust Electric gauges, I prefer mechanical. When reading electric gauges, I try not to let #'s bother me to much. What I do look for is what's normal and when I see something that isn't normal, then I know I have an issue. So if it's normal to see it on the first notch at idle, and jump to the 3rd notch on the throttle, and then all of a sudden it's different than that, then it's time to investigate.

I can certainly understand wanting to keep the same OEM gauge in the dash, so keep that, but if you have or can find a mechanical gauge at DIY yard, or buy a cheap one, then hook it up under the hood with some brass fittings so that when you're tuning or working on it under the hood, then you can KNOW your mechanical gauge is good.

On my 64 JeemC, I had an Oil Pressure, Fuel Pressure and Vac Gauge hooked up under the hood and mounted in various places. Also came in handy when tuning or when I'd have an issue out racing.

 

[Irishman999]

It could even be in the gauge sender Dawg. And you mention it did the same thing with the old motor? So that's a good thing really. Honestly, I don't trust Electric gauges, I prefer mechanical. When reading electric gauges, I try not to let #'s bother me to much. What I do look for is what's normal and when I see something that isn't normal, then I know I have an issue. So if it's normal to see it on the first notch at idle, and jump to the 3rd notch on the throttle, and then all of a sudden it's different than that, then it's time to investigate.

I can certainly understand wanting to keep the same OEM gauge in the dash, so keep that, but if you have or can find a mechanical gauge at DIY yard, or buy a cheap one, then hook it up under the hood with some brass fittings so that when you're tuning or working on it under the hood, then you can KNOW your mechanical gauge is good.

On my 64 JeemC, I had an Oil Pressure, Fuel Pressure and Vac Gauge hooked up under the hood and mounted in various places. Also came in handy when tuning or when I'd have an issue out racing.

Its not the sender, I bought two of those MF'ers just to be sure. I have a mechanical gauge too, I might go plug it in and check it out. Most likely I will just put the new electronic one in and hope it fixes my issue, if not I will keep speculating about it on the internet and rebuilding engines.

 

[bigcountryguy19]

Maybe try just putting a set of new lifters in, since it was pouring oil out of the one rocker, seems like there is something going on with that one component. Doesn't matter were it loses oil, it should still affect oil pressure, like a pipe with 50 spigots, no matter where you turn one on, the pressure in the hose will decrease. It's basic hydraulic theory. Flow finds the path with least resistance, and more flow will decrease pressure. Until you rev it because now the pump is putting out more oil.


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[chevyk10]

Just to speculate: what about the oil pump sucking some air like a pickup issue. Rare I know


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[anubisani]

I wld check the cam bearings and make sure the are lined up correctly with the corresponding holes, just my 2cents, also did the cam have a hard time going in , I had that problem before and after I got it in the oil pressure was low think I damaged something

 

[HotRodPC]

I'd agree, Cam bearings would be the FIRST place I'd be going once I KNOW for a fact, I have an accurate gauge and KNOW for certain there is an actual problem. I have a feeling there is nothing wrong and it's the gauge or sender. He says he's verified the sender to be KNOWN good, so we'll see what happens after he replaces the gauge and/or gets a manual gauge for underhood hooked directly the motor. If the issue is verified that there's a problem, then yep, CAM bearings is first thing to check. Because, surely he platsigauged every main and rod bearing and KNOW they are good to go and that the crank journals are all in tolerance. If they weren't, then I'd consider some .001 oversize main and rod bearings. But I don't recall if he had the crank turned or not. Figured before I got into all of that, we'd get through step 1 first and verify he has accurate readings.
I just really hope it's gauge related. To much money and time involved in this build to have issues.

 

[Irishman999]

Maybe try just putting a set of new lifters in, since it was pouring oil out of the one rocker, seems like there is something going on with that one component. Doesn't matter were it loses oil, it should still affect oil pressure, like a pipe with 50 spigots, no matter where you turn one on, the pressure in the hose will decrease. It's basic hydraulic theory. Flow finds the path with least resistance, and more flow will decrease pressure. Until you rev it because now the pump is putting out more oil.


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You are totally on the same wavelength as I am, there was enough oil gushing out of that one rocker I remember making this mental note, "if I have any oil pressure issue I will check out this rocker gushing oil". There is way to much oil coming out for it to be a normal thing. I wont pull all the lifters, I can order single ones from comp cams in case this one is damaged.

Just to speculate: what about the oil pump sucking some air like a pickup issue. Rare I know


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Not rare at all but its not the issue. New o-ring and tack welded the pickup tube to the pump.

I wld check the cam bearings and make sure the are lined up correctly with the corresponding holes, just my 2cents, also did the cam have a hard time going in , I had that problem before and after I got it in the oil pressure was low think I damaged something

I installed them myself with a special installer, I used paint to ensure the holes were aligned perfectly. I botched the first install and learned enough to install the second set flawlessly. I quadruple checked the cam bearings, I even had conversations with my machinist about it to ensure I did it right. Its not the cam bearings, those are ****. If the cam bearings were out of tolerance it would not be building so much oil pressure after startup, that is why I am thinking its the gauge.

I'd agree, Cam bearings would be the FIRST place I'd be going once I KNOW for a fact, I have an accurate gauge and KNOW for certain there is an actual problem. I have a feeling there is nothing wrong and it's the gauge or sender. He says he's verified the sender to be KNOWN good, so we'll see what happens after he replaces the gauge and/or gets a manual gauge for underhood hooked directly the motor. If the issue is verified that there's a problem, then yep, CAM bearings is first thing to check. Because, surely he platsigauged every main and rod bearing and KNOW they are good to go and that the crank journals are all in tolerance. If they weren't, then I'd consider some .001 oversize main and rod bearings. But I don't recall if he had the crank turned or not. Figured before I got into all of that, we'd get through step 1 first and verify he has accurate readings.
I just really hope it's gauge related. To much money and time involved in this build to have issues.

Crank got a micro polish job, every journal got plasti-gauge. In a general sense the bottom end was assembled loose, I did that on purpose. I could have gone +1 on some of the rod bearings but I wanted a looser bottom end. It was nothing out of tolerances or anything but it was just a loose enough crank I could have gone oversize with bearings, I had this conversation with the machinist.

Its got plenty of oil pressure, after thinking about the problem enough I think its a dead spot in some contact in the gauge. Also something with that rocker, looking into both things.

 

[highdesertrange]

just like what been mentioned here several times check with a mechanical gauge. I have several sending units be bad from a major parts chain. turns out they were selling idiot light sending units in place of gauge units. once I discovered this they didn't want to believe me because their computer said it was the right part. once you get a reading with a mechanical gauge check your sending unit with an ohm meter. you can check your electronic gauge with a resistor box to check for accuracy. highdesertranger

 

[bucket]

Agreed, check with another gauge.

What are you doing for an oil cooler? Are you running one at all? Reason I ask is the cooler ports that are on the gen 5 and 6 blocks, if they are just plugged off it will cause oil pressure issues. If those two ports are blocked, you are supposed to remove a bypass valve that is located in the center of the oil filter mount. That's what I've got from my research anyway, trying to figure out a cooler setup on my motor swap. Right now I'm leaning towards hooking a cooler to those ports, just to play it safe.

 

[Irishman999]

Agreed, check with another gauge.

What are you doing for an oil cooler? Are you running one at all? Reason I ask is the cooler ports that are on the gen 5 and 6 blocks, if they are just plugged off it will cause oil pressure issues. If those two ports are blocked, you are supposed to remove a bypass valve that is located in the center of the oil filter mount. That's what I've got from my research anyway, trying to figure out a cooler setup on my motor swap. Right now I'm leaning towards hooking a cooler to those ports, just to play it safe.

Gen VI blocks have oil cooler ports built into the block on the same machined level the oil pan bolts to. Mine are blocked off, I am currently running no oil cooler even though I have a brand new sandwich adapter kit ready to go. There is two check valves in the area you are talking about, the center one I might have to check out but the one that matters when doing a oil cooler setup is the outside bypass valve, it has to be switched out to a 30psi unit if you run an oil cooler or some ****. Right now I am just running a filter, next thing I check out will be the check valves.

 

[bucket]

Gen VI blocks have oil cooler ports built into the block on the same machined level the oil pan bolts to. Mine are blocked off, I am currently running no oil cooler even though I have a brand new sandwich adapter kit ready to go. There is two check valves in the area you are talking about, the center one I might have to check out but the one that matters when doing a oil cooler setup is the outside bypass valve, it has to be switched out to a 30psi unit if you run an oil cooler or some ****. Right now I am just running a filter, next thing I check out will be the check valves.

Mine is currently setup for a cooler from the factory, I was researching how to safely plug the cooler holes. When you say "outside" do you mean still within the oil filter pad, just not in the center?

 

[bobkyle2]

Wow, this is a mess...

Do not go any further until you put a mechanical gauge in it....

When its sitting at zero, Does it rattle? If you truely have zero oil pressure your going to have alot of chatter.

Lifters will not affect oil presure ... (Remember you can creat oil pressure by pulling the distributor and putting in the pump driver and spinning the oil pump with a drill.. That throws the lifter scenario out the window..)

 

[Irishman999]

Wow, this is a mess...

Do not go any further until you put a mechanical gauge in it....

When its sitting at zero, Does it rattle? If you truely have zero oil pressure your going to have alot of chatter.

Lifters will not affect oil presure ... (Remember you can creat oil pressure by pulling the distributor and putting in the pump driver and spinning the oil pump with a drill.. That throws the lifter scenario out the window..)

Run the lifter scenario explanation by me one more time, not sure what you mean exactly. Just curious, do you guys think I will have good oil pressure if I totally remove a lifter from the bore?