oil psi ??

[jessie355]

was wondering if u could help me i have a 400 sbc 30 over just built not too long ago it has 2300 miles on it . when u first start it up it has good oil psi till it warms up then it gets really low to day i drove to the store and when i stoped at a stop sign the oil psi droped to 0 but it only does it if ur holding the brakes if u put it in nutral it gets about 10 to 15 psi only time it hits 0 is when u start to put on the brakes and when braking for turns it drops intstantly. i tried a new gauge but its still the same

 

[Bigblockguy]

1. Have you changed the oil a couple times since the rebuild?
2. What kind of pickup? bolt on or press?
3. who did the rebuild and were bearing clearances in spec?
4. oil pressure cold/ what oil?


Sounds like the oil pump pickup could have fallen off, Or you have some bearings wiped out. I would drain the oil and look for material and cut open the oil filter.

 

[jessie355]

1. Have you changed the oil a couple times since the rebuild?
2. What kind of pickup? bolt on or press?
3. who did the rebuild and were bearing clearances in spec?
4. oil pressure cold/ what oil?


Sounds like the oil pump pickup could have fallen off, Or you have some bearings wiped out. I would drain the oil and look for material and cut open the oil filter.

yea changed it three times and a press in pickup my buddy that used tobuild 400s for a machine shop and the crank was turned 10/10 and cold oil pressure cold is 50 with 10w 30 full synthetic

 

[Bigblockguy]

In that case pull the pan and I bet you'll find the oil pump pickup at the bottom. Chances are the reason you are seeing a drop in psi while braking is oil sloshing out of the sump and the pump is high enough that it's sucking air/oil.

Good luck

 

[Goob]

Try another gauge first, to verify the actual pressure.

Is the filter by-pass plugged?

10-20 psi idling hot would not concern me with a stock oil pump. I think a pick-up problem would drop pressure during a stop then bump back up sitting still. 0 at idle is a little scary.
Hydraulic or mechanical cam?
Oil restrictors to the upper end?

If it is a hydraulic cam, and the pressure is truly zero, you would get some lifters clacking if you idle very long.

Oil pan and dipstick are matched and correct?

 

[Bigblockguy]

Try another gauge first, to verify the actual pressure.

Is the filter by-pass plugged?

10-20 psi idling hot would not concern me with a stock oil pump. I think a pick-up problem would drop pressure during a stop then bump back up sitting still. 0 at idle is a little scary.
Hydraulic or mechanical cam?
Oil restrictors to the upper end?

If it is a hydraulic cam, and the pressure is truly zero, you would get some lifters clacking if you idle very long.

Oil pan and dipstick are matched and correct?

Says he tried a new gauge. That was my first thought to.

 

[malibuman327]

id say the bearing on the crank are bad thats whats happen to me it ran good but the pressure got to like 5 psi the one day and turned out there was alittle more wear on the crank and bearing then we'd like so got it cut and polished and new bearing and a new oil pump just to be on the safe side and its fine now.

 

[Anonymous]

your not running a high volume oil pump are you? If so all of your oil is on the top end when you come to a stop and your motor is starving for oil on the bottom end. I would just replace that oil pump with a stocker...it's more than adequate.

I had a 350 lose the pick up tube too once that had similar symptoms as was suggested earlier.

 

[malibuman327]

really??? you mean after i replaced it with a new one because i get great oil pressure now and it seems okay.

 

[7d8ss]

It almost sounds like an electrical issue. When the brakes are applied, (even at a stop) the oil pressure drops at the gauge. Is your gauge electrical or pressure activated? _ Jon