Dave,

I think you are right....but why would this just all of a sudden happen?

CmanZ28

 

Loose main brgs will do that under a load,but it might be the sender(I don't think so)

If it's under full throttle the oil is climbing the back of your stock pan.If it isn't only under part throttle at 4000 then the oil isn't climbing. And no it isn't caused by windage or every SBC would have the problem.They make a plate that bolts under the pump to help stop the climbing.Or better yet a GOOD pan.

 

Those are some words I didn't want to hear!!! But is there anything I can do to check this other than taking the pan off?

CmanZ28

 

Does it do it at 4000 under part throttle or full throttle?

 

Full throttle

 

My guess is ya got the stock oil pan blues. The oil(especially without the baffle) under accelaretion climbs the back of the pan and lets the pickup suck air.If ya keep doing it ya will blow the motor.
Ya probably need a Good pan and pickup to cure it's ill's.

 

My suggestion would be to install a gage to monitor oil pressure to be certain the sender and/or harness, gage malfunction is not causing a false reading. Does the oil pressure drop under heavy decelleration / braking? Are you sure the dipstick is accurate? If you are not sure, you can drain and refill to rule that out. If the oil level is correct and the pressure drop under heavy braking the oil pick-up may have dropped into the pan. I have had this happen to me twice once on a big block 396 and once on a small block 400. You would not think it can fall off because it is pressed in but it can. One way you might be able to find out without dropping the pan is to use a coat hanger to probe around thru the drain plug hole to see if it is loose in the bottom of the pan. That is how I confirmed my 400 had dropped it's pick-up. GOOD LUCK and hope you can figure out what it is before you tear into the engine. I do not think your bearings are shot. Oil pressure would be very low at idle when the engine is hot. I have never seen excessive bearing clearance drop under load at 4000rpm and then not drop at no load at 4000rpm. If the pick-up is in the pan or if the oil level is low the oil presure can drop under heavy acceleration or de-celleration.

 

No this problem is only under hard acceleration. When I put the clutch when this happens my oil pressure shoots right back up to around 40 psi.

I changed the oil 1000 miles ago and I put in 5 qts and a new filter. It has been on full (dipstick) since then...so I think my oil is the correct level.


In what order should I take the steps?

1. Change oil /filter to 20W50?
2. Hook up manual oil pressure guage?
3. ????

Thanks in advance
CmanZ28

 

Thanks Larry,

Should I still go through the trouble of changing the oil to 20W50 and putting on a manual oil pressure guage? Or just go straight for a new oil pan and pickup?

CmanZ28

 

Loose mains will cause the under load problem. If ya haven't seen it maybe it's because ya don't have enough years in the business and had engines that exhibit the same symptoms.

 

I would go to the trouble, it's an indicator of the problem. If the 20/50 brings it up then ya can look at the brgs,and if the manual guage says different then it's the guage or sender. Minor work compared to the pan if it fixes it.

 

Ok thanks 1racerdude.

I'll report back tomorrow nite after I get the oil changed.

Thanks Again!!!

CmanZ28

 

Sounds like it would be worth trying to rule out the pick-up fell off by probing the oilpan thru the drain plug hole with a coat hanger. This is quick and easy and worked for me. Your symptoms sound exactly like what my cars did after they dropped the pick-up. Hard accelleration or braking will make the oil pump cavitate and the pressure will drop. Good luck finding the source of your problem! Don't worry that your bearings worn out, the symtoms you describe are unlikely to be caused by excessive main bearing clearance

 

cat1055man

I will definitely do that when I change my oil?

Thanks,
CmanZ28

 

OK,

I changed the oil to Castrol 20W50 Synthetic Blend. My warm Idle oil pressure is now at 30 Psi!!!!!!!! I went out for a drive to check if the oil pressure drops much under full throttle.....well, it does a little bit but the oil pressure never drops more then 5-7psi. and the oil pressure is right around 50psi then drops to maybe 45 or 42psi. Is this acceptable?

CmanZ28