408 oil pressure problems

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mopar_persson

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hey have some problems whit new engine (it is a 360 stroked to 408) and that is that it loses oil pressure almost down to 0 under heavy acceleration,oil pressure is 58 psi normally, oil pan is a completely original 360 passenger car pan, oil pickup is about 0.78 inches from the pan bottom.

I have tried many different oils with the same results all times
The oilpump is a brand new Melling original pump, no high volume pump

what should I do?
 
Mechanical or electric gauge? My first thought was the pickup being on the bottom of the pan. Second thought maybe the gauge or sender unit if electric.
 
mopar_persson said:
hey have some problems whit new engine (it is a 360 stroked to 408) and that is that it loses oil pressure almost down to 0 under heavy acceleration,oil pressure is 58 psi normally, oil pan is a completely original 360 passenger car pan, oil pickup is about 0.78 inches from the pan bottom.

I have tried many different oils with the same results all times
The oilpump is a brand new Melling original pump, no high volume pump

what should I do?
Click to expand...


if you are losing pressure under Heavy acceleration and the pan is stock...you need some baffling in the pan to keep the oil from exposing the pickup during the heavy acceleration...
 
70aarcuda said:
if you are losing pressure under Heavy acceleration and the pan is stock...you need some baffling in the pan to keep the oil from exposing the pickup during the heavy acceleration...

I agree, a 408 with some bite can easily send a 5 qt. pan up the back side. Especially picking up 3/4" off the floor.
Click to expand...
 
If its mechanical might be rod bearings. I remember when mine when cold start up dropped from 70-80 to 60 and hot idle to 20 from 30-40. And that was a stock pump and pan and clearances.
 
The pickup needs to be down near the pan. I aim for .125 (1/8") and check it using clay and no gasket. That way once the gasket's in place you have right around or just under .25" when everything is together. In normal operation the oil is pumped up and has to flow back down to the pan around the crank. Adding drain holes in the valley, tapering the holes, and adding a scraper helps the oil return faster. A windage tray will also help keep oil from getting trapped around the crank itself. I think your issue is a combination of too much air under the pickup causing it to suck air when the oil moves in the sump and slow drain back. I would suggest pulling the pan, properly fitting a windage tray, and lowering the pickup to less than .250".
 
moper said:
The pickup needs to be down near the pan. I aim for .125 (1/8") and check it using clay and no gasket. That way once the gasket's in place you have right around or just under .25" when everything is together. In normal operation the oil is pumped up and has to flow back down to the pan around the crank. Adding drain holes in the valley, tapering the holes, and adding a scraper helps the oil return faster. A windage tray will also help keep oil from getting trapped around the crank itself. I think your issue is a combination of too much air under the pickup causing it to suck air when the oil moves in the sump and slow drain back. I would suggest pulling the pan, properly fitting a windage tray, and lowering the pickup to less than .250".
Click to expand...

X2 On Moper's suggestions.

Pat
 
Add baffling to the pan to keep the oil from running away from the pickup during hard acceleration....
 
Thanks so much for all the answers :)

the gauge is an electric, and when the engine lost oil pressure, I hear it directly when rocker arms begin to rattle.

I'm going to put on a larger oil pan on the engine and a windage, and buy a new oil pickup.

:cheers:
 
Had the same issue with a 360 when I put sticky tires on the car and got it hooking good. A pan with an acceleration baffle cured it.
 
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