BBC oil pressure problem

Well it seems as thou my 468 bbc will not hold oil pressure for very long before it slowly starts to fall. It will start at 80 then go down to 20 once the car is warmed up. I have replaced the oil pump with a high volume pump (moroso) running 50w oil. The person I bought the car from said it was bord out 100/over and that the block has been concreted up to the water pump, but new little about the motor. The motor runs cool and has not over heated, due to it only cooling the top half. I have run the car at the track, but when I saw the oil drop I turned it off. We did check the mains after that day, and every thing looked good. Also when you raise the rpm the oil does go up to 40-45 @ 3000, but will drop to 20 at idle. What would cause the oil to drop so low? Thanks for any help.

Robert

 

My 460 BBC has been like that for about 15 years and hundreds of passes.

It's normal.

 

too much clearance in the rods and mains will let the pressure drop.. 20 is fine at an idle and 45 is ok at 3k .. id bet its all bearing clearance. I had a 283 i built once that had 40 lbs running at about 3k and 5 at an idle never could kill it it ran forever..
Dave

 

Too much clearance . Engines run on a percentage of leak in the oil system. The greater the % of leak the lower the total oil press at operating temp. Check clearances,make sure all internal oil gallie plugs are in place and last check the oil temp>>>>.

 

sounds like the engine was built with the rod and main bearings at the loose end of the clearance scale. I ran the 468 I had over 300 passes like that before I finally spun the center main bearing.

 

What's the oil pan capacity, and what oil drainback mods have been made?

 

Sounds fairly normal to me......I remember some guys running in the old econo-dragster classes that would consistantly kick everyone's collective asses. It wasn't till they retired that they told everybody what they were doing.............they had dyno'ed race motors with the usual mongo race pump and then swapped it with a "detuned" stock pump. The result was a significant HP increase.......enough to win their share..... It wasn't just the HP lost turning an oil pump, but it was also less oil spray or "windage" the crank has to fight through....If I remember right they said they went thru the traps @ 8000 rpm with 25 psi.........something to think about.......

 

Titan internal oil pumps work well.
Single stage Moroso external pumps work great.
( it will end your worry)

The 20 lbs. idling is common ( as said by others here)
stick with 50 weight oil......

 

Rule of thumb I was taught years ago was 10# pressure for every 1000 rpm's is enough. Consider this, although some don't believe it. You can have to much oil pressure. If the pump, because of pressure, can't turn as fast as the cam wants to turn it you will strip the gears off the cam and dizzy. I know this to be fact because it cost me two BBC's before we figured it out.

 

7 qts

 

We struggled with this problem last year . We run a donovan block and had the same pressure drop after a short warm up. Heres the test. Pull the oil pan off, put a bucket wth oil in it under the oil pump [pump sitting in oil for pick up].Pull the distributor and spin the pump like youre priming the motor.In our case, a loose lifter bore was leaking the oil pressure out. When you spin the pump, you can see the oil pouring out of the bad spot, liftr bore, rods, mains, etc. Works great.We never would have guessed a lifter bore. Good luck.

 

Go get a bottle of Motor New if your worried. I built a few that were a little wide on the bottom end and low pressure was expected at warm up. Usually we routinely pulled them down after a season and went back through them to catch any problems before they manifested...part of racing.

 

i dont think this is your problem but fram oil filters are doing this now,it seems that they cant handle high pressures and come apart internally and cause low o.p.

 

It takes 17 HP to run a oil pump!!!!! Now take off the fuel pump and the magneto>>>>.

 

Probably not your issue,but my 454 street motor for years dropped pressure above 3000. Drove that way many years and asked a lot of people before finding the oil pickup bottomed out on the pan.

 

I know a good mechanic

 

just drop it off over here robert. you don't want that junk anyways.

 

See if a bottle of Lucas will help the cause, although I wouldn't be too worried.

 

Thanks everyone. I did take the car to the track last night and had no problems. Ran a 6.98 6.99 6.85 in the 1/8 foot braking it. Then tried to go faster by using the transbrake and kept making mistakes. Guess I need a lot more seat time.

Thanks again everyone Robert

 

Get some more of that seat time and lets line-em-up..... Mo-Kan here we come !

 

MoKan Fo sure!

 

Lets see the timing slips !

 

You must believe Danny. It's the only thing that will set you free!

 

LOL!

you couldn't get a 55 chevy to go that fast if you pushed it out of an airplane!

damn bricks on wheels!

 

Not that, just like to see the 60 ft times etc .

 

too much clearance between cam bearings and cam