Oil Pressure

I have a buddy with a blwn alky car and his oil pressure gets down to as low as 25 lbs near the end of a run, it has plenty of oil in it and the restrictors that BAE suggested, it has 150 or so at stage then continuously drops through the 1/8th mile. He has a BAE Billet Block and is catching his oils pressure from a V-300 sensor at the System One Oil Filter. Any suggestions?

 

you don't say if the car has a dry sump on it. It sounds like it is running out of oil. You need about 17 litres in a dry sump to make it on a PSI car.

 

more more more oil !!!!!!!! ...also pre heat the oil with a pan warmer from wal-mart 8 - 10 $ it fix all of our problems. Dave

 

It takes a tremendous amount of oil to maintain 150 pounds at stage. Probably need a 55 gallon drum for a dry sump tank. Turn the pressure down.

 

Wet sump with 13 qts, car only runs 1/8th mile.

 

If your friend has even slightly larger than normal main and rod bearing clearances maintaining that kind of oil pressure takes a lot of oil from the pan. 1/8th mile is only 2 seconds shorter than 1/4 mile. It is obviously running out of oil even with restrictors.

The last time I ran a wet sump was in 1997. Pete was making license runs at Bakersfield (screw blower). The tree screwed up and he was at stage RPM for 8 seconds before he left with *only* 120 pounds of oil pressure. By the time he got to the 1/8 mile the pressure fell and it kicked the rods in the lights. I had 12 quarts in the pan.

A long time ago I had discussions about this with Steve Plueger. Nitro FC's leave off an idle and don't run out of oil. Why? Because the RPM is at 8,000 or so for less than 5 seconds on a run. The average number of crankshaft revolutions in a quarter mile run for them is less than 650. In an alcohol car making a 5.80 run, including stage rpm for 5 seconds is around 1,350. Both have the same blocks, cranks and oiling systems.
With blow by through the rings heading out the valve cover breathers keeping the oil from returning to the pan, the nitro car goes 4.8 seconds without return while the alcohol car has approximately 5 seconds at stage rpm plus 5.8 seconds for the run for a total of almost 11 seconds without oil returning to the pan. Look at your watch. That's a long time to be sucking oil from the pan, especially when maintaining that high of oil pressure.

Oil pressure is like blood pressure. Higher isn't always better. In fact it's not good for you. It takes energy (power) to maintain, a larger reservoir is required to feed it and it's not necessary if everything is right.

In 2005 when Larry Miner was driving my car in the semi finals at Tucson we lost a rear main bearing on the burnout (another story). Larry pointed to the oil pressure guage as he was pulling up to stage. It said 40 pounds. I gave him the GO anyway sign and he did. Larry legged it out to a 5.97 and we won the round against Doug Gordon. We took it back to the pits and discovered that the rear main bearing was gone which let the clutch eat the bellhousing so we couldn't return for the final. I looked at the computer and it said we had a maximum of just 60 pounds of oil pressure for the entire run, and Larry shifted it at almost 10,000 from second to high. My guess was that it blackened the crank at each of the rod journals and tore up the mains. To my surprise, even with all the debris from the rear main floating around in the oil the rod bearings and journals were perfect (except for imbedded debris). So were all the push rods and adjusters.

Now I wouldn't recommend going that low, but I can tell you this. Mike Gruber from Valvoline didn't seem to surprised when I told him that story.

 

Well he checked rod nearings last night and it tried to spin #1 bad enough that the rod is going to be replaced, and #3 it blackened really bad and tried to spin. The crank cleaned up just fine with emory cloth and has no damage what so ever to my surprise. Are you saying Randy that maybe he should reduce oil pressure to keep it in the pan longer?

 

There is a pan builder in Oklahome that has a cure for your problem. Call me at 620-663-4949 and I will hook you up. Jerry

 

I say you need more oil. The last 4 brad combos I've worked with have needed 14qts min. all 4 have been wet sump with a Dan Olsen pan. 2 of the motors needed 16 but those motors were set on kill, 5.20's on water.

 

What about external oil returns(from the heads or valve covers back direct to the pan) ? Would this help?