my 68 Malibu has a fresh(approx 500 miles)professionally built 406 sbc. 10/1 comp,294S cam,Holley dual plane,Demon carb,MSD ignition,Doug's headers,etc. All in all, a pretty straight forward set-up. trans is a T350,12 bolt rear, 3.31 gears.

when I was putting it away for the winter, I was playing around and ran it through the gears hard. the weird part is that when I was accellerating hard, the oil pressure dropped from 50lbs to 20lbs at 5500 rpm.as soon as I backed off, the oil pressure recovered. it acted exactly like the oil was sloshing around and starving the pump.now I know the pick up is in the rear,the stock oil pan was full with a fresh oil change and 5 quarts of oil. how can this happen?

Well it did. Hi volume pump, stock capacity pan? Fwiw, I had to run the 427 1/2 qt over so I didn't see psi drop at 6500+.

thanks, easy fixes are the best!

Mine does it at the track all the time,look down at the end of the track and its down to 25-30 psi. I don't think its the hi volume pump,I think it is windage,the crank blowing it away from the pickup,as soon as I let off,it goes right back up,and its been doing it for 2 years now. A little more oil might help,or it could hurt, just be more oil getting slung around in the crankcase.

Originally posted by swm233:

...when I was putting it away for the winter, I was playing around and ran it through the gears hard. the weird part is that when I was accellerating hard, the oil pressure dropped from 50lbs to 20lbs at 5500 rpm.as soon as I backed off, the oil pressure recovered.... swm233,

Had a similar problem with my 327. Oil pressure would start to drop at 5,000 rpm. Pulled the engine, replaced the new Melling hi volume pump and pick up with a Melling standard flow unit and a new pick up. Problem gone!

Mike

thanks guys. I knew it couldn't be the oil being thrown rearward, that would push it back toward the pick up. I am going to try running it a little over full to see if that helps. if it doesn't help do you think there is enough volume to compensate for the low pressure? or am I causing damage?

I run a Sealed-Power high volume pump on my 454 and my pressure is around 65 psi at the far end of the track. I do run a factory windage tray and also use a custom made 7.5 quart pan.

With a 406 you can be having windage problems depending on the oil pan and tray setup. Normally a SB won't drain the pan dry even with a stock pan and a HV. pump. You need to take a good look at what you have most pans weren't really designed for a 3.75 stroke crank.

That's an old trick used by the old time racers. Run an extra quart because at higher RPM's the oil is up top and slow on returning to the pan.

the pf 35 truck filter will give you 1 more quart of capacity than the pf 25 filter. use it and you can run 6 qts of oil.

See my post, finally figured out a similar problem!

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic&f=4&t=017754

I agree w/ Robert that your problem is windage. I had a similar problem on a 350 with a Milodon 6 qt Vega Conversion Pan. It would start to drop oil pressure from 65psi to 40 psi at 5200 RPM. Changed to 10-30 oil and ran it 1/2 quart low and no more problems. Once I got oil control solved, it was not a problem. I would reccomend installing a windage tray if you can. You can buy the GM bolts with the standoff for the tray so you don't have to worry with studs.

I have the same problem with my 383, and have concluded that it is windage. I have a windage tray, but it does not adequately cover the sump area. I plan on replacing it with p/n 20-908 from Canton Racing Products. Check it out.

Windage Tray (http://www.cantonracingproducts.com/windage_trays/windage_trays.html)

Did you leave the O rings off the distributor shaft at the bottom? That will cause the same affect. Did this while engine was on the dyno. Made a pull with the O rings on, no pressure drop, took them off, dropped to 25-30 pounds starting at 3500 RPM. FYI

Fresh oil change you say - Fram oil filter?

I had the same thing happen with a 350 in my camaro. Got rid of the fram and the problem went away.

lots of ideas. I am sure with all these suggestions, I will find the problem. thanks!!

If you run an extra quart on the street though youll end up whipping the oil. The correct way to fix it would be to buy a good 7qt pan. And unless you need a HV pump for some reason switch to a Z-28 pump and you should have adequite oil pressure. Im getting rid of my HV pump, and im also getting rid of the "direct lube" lifters that kill my oil pressure. Boy did i get suckered on that one.

Originally posted by Nickel333:
...... And unless you need a HV pump for some reason switch to a Z-28 pump and you should have adequite oil pressure. Im getting rid of my HV pump, and im also getting rid of the "direct lube" lifters that kill my oil pressure. Boy did i get suckered on that one. The spring is still available to convert any standard Melling SBC pump to a Z-28 pump at your friendly Chevrolet dealer.