Oil Pressure Drop Help....

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"Dart67"

"Dart67"

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I finally was able to take my car "Home-Brewed" out for about a 4 mile drive this morning.

Runs pretty well.

BUT... I was logging the drive by way of the F.A.S.T. XFI and there seems to be an OIL PRESSURE problem.

I am using Rotella 15W 40 oil.

8 Quart pan and external pickup standard volume melling pump.

At Cold start the pressure is at 70 PSI.

As the engine warms up the pressure slowly drops to around 25 to 30 PSI. I can live with that.

What I can't live with is that after I accelerate pretty good and back off the pressure is dropping to near ZERO.

Sometimes it comes back up Sometimes it dose not.

Could the relief be sticking?????

ANY Guidance will be appreciated.

"Dart67"
 
If you didn't say 8 quart pan, it would sound like you were sucking the pan dry and/or had an oil drainback problem. On my old 400 the lifters would get noisy after a full throttle burst, and that's what I chalked it up to.
 
Eight quart deep or rally racing pan ??
If it’s rally it could not be returning Enugu oil to the sump on a burst of power
 
When you say it warms up and drops to 25-30 psi that's at idle I hope? What is it doing at cruise and WFO?
A good first step is to connect a good mechanical gauge and re-test.
If you suspect the relief valve is sticking open, it's not hard to take it out and inspect/clean the spring and poppet. See if there's any crusty-ness in the passage where the poppet rides. You can do this without removing the pump.
That said....I don't know if a sticking valve would render close to ZERO psi?
 
beanhead said:
When you say it warms up and drops to 25-30 psi that's at idle I hope? What is it doing at cruise and WFO?
A good first step is to connect a good mechanical gauge and re-test.
If you suspect the relief valve is sticking open, it's not hard to take it out and inspect/clean the spring and poppet. See if there's any crusty-ness in the passage where the poppet rides. You can do this without removing the pump.
That said....I don't know if a sticking valve would render close to ZERO psi?
Click to expand...

nothing wrong w/ 25-30 at hot idle , mine doesnt that much---------
 
What I wanna know is, what's the justification for an HV oil pump if he has an eight quart pan with a stock volume pump? He's certainly not pumping the pan dry.....not that he would with an HV pump either. If he's dropping to zero at any time whatsoever, he's got a problem somewhere. No baffles in the pan even with eight quarts could still uncover the oil pickup on braking or acceleration. Also, I saw no one ask which pickup he has. Is it a stock pickup with an eight quart pan? If so, there's your trouble right there. A deep pan MUST run a matching longer oil pickup tube that makes contact with the bottom of the pan, just like the factory did it, otherwise, it's entirely possible enough oil is being pumped out of the pan to uncover the stock pickup, even with a stock pump. It's an oil pump. Not an air pump.
 
Pretty Much have the Oil Pressure issue Solved/Fixed.

Last Friday I took the car for a short test drive. As I crossed a small bridge on the road the oil pan meet the only high spot on the bridge deck.

DSCN0943.JPG


I got turned around and back to the shop (about a 1/4 mile) with about 4 quarts of oil left in the pan.

I now have the pan repaired and back on.
Yes, this pan has baffles in both the front and rear of the sump area.

This is when the pressure problem came up.
Normally I run straight 30W oil.

I did not have any on hand. SO, I used what I had 15W 40.

I went to town and got 8 quarts of 30 W and changed the oil. (Typo should be Straight 40W)

I have 3 oil pressure senors and gauge on the car. One pressure sensor for the F.A.S.T. XFI. A Autometer Electric pressure gauge and a Mechanical gauge on the back of the engine.
Now, I can not see the mechanical engine gauge while driving. But I can watch the Dash gauge and I am also LOGGING the pressure on the XFI. These pressures are all the same.

Watching the LOG I can see the oil pressure for the 15W 40 drop as the engine temp comes up to the point of almost nothing..
With the 30W I can see the oil pressure also drop as the engine warms up. But it seems to stay at 25PSI. Give or take a pound or two.
 
Last edited:
Sorry that's what it was, but glad you got it figured out.
 
"Dart67" said:
Pretty Much have the Oil Pressure issue Solved/Fixed.

Last Friday I took the car for a short test drive. As I crossed a small bridge on the road the oil pan meet the only high spot on the bridge deck.

View attachment 1715761699

I got turned around and back to the shop (about a 1/4 mile) with about 4 quarts of oil left in the pan.

I now have the pan repaired and back on.
Yes, this pan has baffles in both the front and rear of the sump area.

This is when the pressure problem came up.
Normally I run straight 30W oil.

I did not have any on hand. SO, I used what I had 15W 40.

I went to town and got 8 quarts of 30 W and changed the oil.

I have 3 oil pressure senors and gauge on the car. One pressure sensor for the F.A.S.T. XFI. A Autometer Electric pressure gauge and a Mechanical gauge on the back of the engine.
Now, I can not see the mechanical engine gauge while driving. But I can watch the Dash gauge and I am also LOGGING the pressure on the XFI. These pressures are all the same.

Watching the LOG I can see the oil pressure for the 15W 40 drop as the engine temp comes up to the point of almost nothing..
With the 30W I can see the oil pressure also drop as the engine warms up. But it seems to stay at 25PSI. Give or take a pound or two.
Click to expand...
Personally I cant see how dropping from 40W to 30W is going to resolve your issue.
What is that big AN fitting for on the side of the pan? The only time I have seen something like that is for a dry sump application.
 
512Stroker said:
Personally I cant see how dropping from 40W to 30W is going to resolve your issue.
What is that big AN fitting for on the side of the pan? The only time I have seen something like that is for a dry sump application.
Click to expand...

That's his external pickup. It goes straight to the oil pump.
 
512Stroker said:
Personally I cant see how dropping from 40W to 30W is going to resolve your issue.
What is that big AN fitting for on the side of the pan? The only time I have seen something like that is for a dry sump application.
Click to expand...
It a single line oiling system. Lots of guys run them. Kim
 
It looks to me that your single line exterior pickup is at the very rear of a very long sump. Under hard braking, im betting the oil is running away from the pickup, in spite of the baffles. I would consider either a swinging pickup more in the center of the sump, or a swinging door in the sump, to allow rearward flow under accel, and block forward flow during decell.
Edit: that is a very long, far forward sump. Modified k-member?
 
33IMP said:
It looks to me that your single line exterior pickup is at the very rear of a very long sump. Under hard braking, im betting the oil is running away from the pickup, in spite of the baffles. I would consider either a swinging pickup more in the center of the sump, or a swinging door in the sump, to allow rearward flow under accel, and block forward flow during decell.
Edit: that is a very long, far forward sump. Modified k-member?
Click to expand...

I think this ^^^^^^ is an excellent theory on what's happenin.
 
512Stroker said:
Personally I cant see how dropping from 40W to 30W is going to resolve your issue.
What is that big AN fitting for on the side of the pan? The only time I have seen something like that is for a dry sump application.
Click to expand...

SINGLE LINE EXTERNAL , SWINGING OR FIXED PICK UP -------------
 
qkcuda said:
If you didn't say 8 quart pan, it would sound like you were sucking the pan dry and/or had an oil drain back problem. On my old 400 the lifters would get noisy after a full throttle burst, and that's what I chalked it up to.
Click to expand...
In the early days of ss racing a 71 cuda on the decel end of the track the pressure would drop and the engine would labor to crank. Really didn't know what was going on. After a catastrofhic explosion we found the oil pan had the baffles removed so the oil would go to the rear at accel and suffer the pickup of oil. hard lesson. Not sure what pan you have but it will move the oil from the pickup to the rear at accelerate if not baffled correctly.
 
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