Newly built motor losing oil pressure at idle

[holiks03cobra]

Been trying to figure this problem out for the last couple months. I’ve pulled the motor twice now for the builder to look it over and they say they can’t find anything wrong. Tried a new oil pump and didn’t fix anything. Cold start it gets 50-70 psi and in about 20 minutes of idling the pressure falls to under 10 psi. I’m sure it would go to 0 but I shut it off. I’m getting “try more oil to there could be a crack in the motor or heads”
The car has been down for going on 2 years and I just want to get it fixed and back on the road. I miss driving it!
Thoughts?

 

[holiks03cobra]

Here’s the build sheet

 

[MG0h3]

I’ve never had one of these apart but isn’t there an oil drain back plug or restrictor in one of the heads?


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[holiks03cobra]

I’ve never had one of these apart but isn’t there an oil drain back plug or restrictor in one of the heads?


Sent from my iPhone using svtperformance.com

I’m not sure. The heads were ported by fox lake so if that stuff doesn’t come out for porting it shouldn’t be an issue

 

[01yellercobra]

I'm pretty sure there's a restrictor in heads as I vaguely remember a thread where someone removed it to get more oil to cams.

I would think if it was a drain back or missing plug somewhere you'd have the issue from first start. Depending on the size of the hole.

Did he replace the whole pump or just the spring?

 

[holiks03cobra]

I'm pretty sure there's a restrictor in heads as I vaguely remember a thread where someone removed it to get more oil to cams.

I would think if it was a drain back or missing plug somewhere you'd have the issue from first start. Depending on the size of the hole.

Did he replace the whole pump or just the spring?

The whole pump

 

[01yellercobra]

Really dumb...but have you double checked the gauge? I once thought I lost an engine but it turned out the line to the gauge was leaking.

 

[Zemedici]

Really dumb...but have you double checked the gauge? I once thought I lost an engine but it turned out the line to the gauge was leaking.

this

is car ACTUALLY losing oil pressure?

 

[03' White Snake]

My oil pressure does the same thing. I check mine on an Autometer mechanical gauge. When hot it drops down like yours, I cannot remember how low (under 20 for sure), but significantly lower than when cold. If I rev it up or am driving it mine goes back up, again, not to cold numbers though. I am running billet gears in a H.O. Cobra oil pump.

I do not think you have a problem. The OEM oil light is a dummy light. 2 psi and the light is off. Your engine is toast by the time the OEM light comes on. You need a quality aftermarket gauge to really check if you have an issue or not.

If your engine builder opened the engine and the oil was not gray from bearings not be oiled, I wouldn't worry about it. You would know real quick if you are starved for oil.... ask me how I know.

 

[gimmie11s]

Really dumb...but have you double checked the gauge? I once thought I lost an engine but it turned out the line to the gauge was leaking.

x3

 

[Blkkbgt]

My oil pressure does the same thing. I check mine on an Autometer mechanical gauge. When hot it drops down like yours, I cannot remember how low (under 20 for sure), but significantly lower than when cold. If I rev it up or am driving it mine goes back up, again, not to cold numbers though. I am running billet gears in a H.O. Cobra oil pump.

I do not think you have a problem. The OEM oil light is a dummy light. 2 psi and the light is off. Your engine is toast by the time the OEM light comes on. You need a quality aftermarket gauge to really check if you have an issue or not.

If your engine builder opened the engine and the oil was not gray from bearings not be oiled, I wouldn't worry about it. You would know real quick if you are starved for oil.... ask me how I know.

View attachment 1748528

I have never put a mechanical oil pressure gauge on these cars.

I do however remember reading something ages ago that the oil pressure light won't come on until it drops below 7 psi. I thought that was insane at the time but now it makes sense as to why ford did that.

 

[gt347mustang]

What is the oil pressure at 3krpm 4krpm and 5krpm when oil temp is 150+? What weight oil? Those clearences are much higher than oem so I hope you're not using 5-20. What port are you using to measure pressure?

The idle oil pressure doesn't matter as long as its moving some oil.

Have you opened up a oil filter yet?

There's a good chance nothing is actually wrong with your engine.

 

[badcobra]

I agree with Scott above. That main bearing clearance is very high for a teksid and likely why your hot oil pressure is so low. You will need to run a thicker oil. Try a 15w-40. If the engine builder checked the bearings, they would have seen severe damage if there really was a problem. I would get some load on it and get it on the dyno ASAP.

 

[holiks03cobra]

Really dumb...but have you double checked the gauge? I once thought I lost an engine but it turned out the line to the gauge was leaking.

I’m using stock and a speedhut gauge. I didn’t see any problems with the wiring.

 

[holiks03cobra]

this

is car ACTUALLY losing oil pressure?

I put a mechanical gauge on but shut the car off when it hit 20 psi

 

[gimmie11s]

20 psi? why?

FWIW, the new 5.0 runs in the low-mid teens for hot idle oil pressure.

 

[holiks03cobra]

What is the oil pressure at 3krpm 4krpm and 5krpm when oil temp is 150+? What weight oil? Those clearences are much higher than oem so I hope you're not using 5-20. What port are you using to measure pressure?

The idle oil pressure doesn't matter as long as its moving some oil.

Have you opened up a oil filter yet?

There's a good chance nothing is actually wrong with your engine.

I’ll have to get back to you on those rpm numbers. Just put everything back together. I was using royal purple break in oil, I believe is a 10w30.

I’m using both ports. One for the stock gauge and one for my speedhut gauge.

Haven’t opened a filter yet. Gonna cut open the one that was just on. I’ve changed the oil 3-4 times now and haven’t seen anything wrong with it.

 

[cobracide]

Make sure the filter has an working oem style bypass valve.

 

[holiks03cobra]

20 psi? why?

FWIW, the new 5.0 runs in the low-mid teens for hot idle oil pressure.

My brother was monitoring the gauge outside the car, I was in the car, he said shut it down. I said where was it? He said 20. Guess he got a little worried lol.

I don’t remember my last motor going lower than 25 but the clearances weren’t this loose

 

[Zemedici]

Better safe than sorry, but as stated, that’s not too crazy