Hello All
I have a strange oil pressure problem. First I must tell you this is a 327/295 SS combo, that came in a car that I bought. The Motor was originally done by Jeff Stealey. The only thing I changed on the motor was the oil pan. The Oil used is 10/30 Brad Penn.

When the motor was started up it had 55 to 60 LBS oil pressure.
Once the motor reached operating temp around 170 degrees, the oil pressure started dropping down to 20/25 LBS of pressure. even if you rev it up, it would only go up about 5 LBS then fall right back down. (this happened while the motor was idling at 1300 RPM)

Cutting the motor off for a few minutes and starting it back up, the oil pressure would again be at 55 to 60 LBS. Once it would run for a few minutes it would drop down again to 20/25 LBS.

I say ok need to replace the oil pump, so that what we did. Guess what it did the same exact thing.
Slightly confused, any ideas?
Would it help if I put 20/50 oil in it?
O yea it never totally lost oil pressure.

Thanks for any ideas or explaintion
Cal

oil pan to close to suction ?
too much clearance on bearings(my personal favorite)

quote:

Originally posted by rusty:
oil pan to close to suction ?
too much clearance on bearings(my personal favorite)

Pick up is 1/4" off bottom of pan.
Bearing clearance was a thought to. But as I said it was a running motor when I bought the car. So without taking it apart can't answer that question.
Thanks for your thoughts.
Cal SST 1177

Change the Convertor

Seems like it is losing volume somewhere after warming up. Didn't change cam/lifters? My first instinct would be the bearing clearances. Maybe lifter clearances? You can check bearings roughly with the pan off. I wouldn't think a weak bypass spring would act this way.

I don't think 1/4 is enough clearance 3/8 to 1/2 is the norm.

is putting the original pan and pickup back on an option? If it is I would start there to see what that does

Drain oil and see (measure) how much actually comes out...could it be low on oil?

If it was fine before you changed the pan then thats your answer, there is somthing up with that pan you installed starving the pump

Didn't do count but add one for clearance.My panel has 454 I built for grandfather and it sat 15 years before I put it on road after he passed.He may have had 3000 miles on it. Crabk it pegs 60 lbs gauge drive it let everything get heat soaked and idle pressure drop to 35 to 45 lbs(nothing to worry about) the drop does get your attention.

I wonder about it and worried a little then remember guy at maching shop has done my work for close to 30 years.90% of motors I was building or me and always on high side of clearnaces,I spin the hell out of my toys.Maybe why I loved the eliminator class that left line at 12000 plus. Figure John just naturally set clearance to high side and I never thought a thing abot it when checked them.

Heck its is sbc and 327's love rpm so little loose is good,we are talking motors not women right.

i remember having this issue years ago and a old mechanic told me it was bearing clearance.he said pull the pump put air pressure on the hole in the block where the pump flow goes out,then watch the crank and see where the most oil comes from.i did and and it was very obvious that the rods were too loose.if you swap pans back that is fairly easy to do in the process

This may sound dumb but could the heat be causing the flat part of the oil pan to bow up some giving you less clearance to the pick up? You could check it with a straight edge before and after to verify.

You say it was a running engine but you didn’t say whether you ran it before and it didn’t do this. We assume it didn’t by your post.

I think you put the original pan back on. If problem is solved then you know the pan you installed is the cause. If swapping pan doesn't fix it then it has to be a problem with internal clearances somewhere since you have already changed pump.

Good morning
Changing the pan back is not an option in this car.
I did hear the motor run, but never ran the motor down the track. Being a SS 9000 plus RPM SBC I would think the clearances would be a little loose. I was just hoping this motor could get me threw a couple races so I could save a little money to replace the broken short block.

O well guess it is just my luck
Cal SST 1177

I agree that 1/4 inch of clearance between the pick up and the pan is not enough. I set the pick up at 3/8 with a steel pan. Since the only change was the pan that is more than likely the problem.

I assume the change was due to a pan/chassis clearance issue, if not re-install the old pan and see if that corrects the problem. Losing that .125 of clearance is probably the cause of your pressure loss.

Bob

aside from what everybody else has said, I would look for a crack in the pickup tube. It would open up when hot and quickly cool off and close back up, giving you the symptoms you described.


Joe

[QUOTE]Originally posted by Cal of MD



Cutting the motor off for a few minutes and starting it back up, the oil pressure would again be at 55 to 60 LBS. Once it would run for a few minutes it would drop down again to 20/25 LBS.

If you had a clearance problem,cutting the motor off for a few minutes would not mysteriously give your clearance back.Sounds like something is being sucked into passage way when started and released and resettle when switched off.Could be something as simple as something being sucked into the oil pressure line/gauge.....And didn't see a mention of checking oil filter...

quote:

If you had a clearance problem,cutting the motor off for a few minutes would not mysteriously give your clearance back.Sounds like something is being sucked into passage way when started and released and resettle when switched off.Could be something as simple as something being sucked into the oil pressure line/gauge.....And didn't see a mention of checking oil filter...

good thought

Just to make sure, you did change your oil filter since the problem started.

Joe

Good morning all.
Didn't think about checking the oil pressure line.
but I will later today. As far as the oil filter, yes it has been changed twice.
Both filters were Wix Filters.
Thanks again
Cal