6.0monsta

iTrader: (7)

What would cause oil pressure to drop only in one gear?

My oil pressure goes to around 50psi in 1st gear until around 5500. Then it drops off to around 34psi at high rpms. As the transmission shifts to second the oil pressure will catch up to around 40psi. Then as the car starts pulling in second gear the pressure will go down to 27psi and stay between 27-34 until redline in second. At 6800 the motor only has 34psi! When the car shifts the 3rd the pressure jumps up to 48psi and stays between 48-52psi through 3rd gear.

This is from a log at the track. Motor is an LS3 427. No idea on bearing clearances but it's built for nitrous so it's lose. Melling oil pump with 15w40 Amsoil oil. Oil temp 172-183 during this run.

Any ideas? I just switched to 15w50 Mobil but haven't floored it yet. I do know that the car has higher hot idle pressure now. The drop in second gear just has me puzzled though.

frito1

iTrader: (12)

Maybe I'm making this too simple but here's what I think is going on....

First and second gears you are pulling a lot of g-forces slamming the oil against the back of the pan away from the pickup. That's why it's good until about 5500 just when you empty the pickup tube. I think you are borderline cavitating the pump. 3rd gear when the g-forces go down some, your pickup is able to stay completely submerged in oil. Might try raising the oil level a touch and see if your log shows good oil pressure. If so, you might want to change the pickup tube to something a little further back.

6.0monsta

iTrader: (7)

Thanks. I made a log on the street last night with the heavier 15w50 oil. Oil pressure looked better but still a tad lower than I'd like to see it. Of course that was from a second gear roll and is different from a full on launch at the track. I think I'll try to top it off a little more maybe half a quart more and see if that helps. I think the 15w50 thickness is helping though. I think the 15w40 I was using just wasn't thick enough in this motor. It's loser for the nitrous. Maybe with the combo of half a quart extra and the thicker oil I'll be where I need to be. I won't know for sure until next time I go to the track. Luckily I think this will only be a real issue when I'm at the track and when it's really hot out during the summer.

thedak

iTrader: (1)

That is plenty of oil pressure.

Add another 1/2-1 quart of oil and don't worry about it.

My engine is .0015-.0018 on 10W-30 I am seeing 37 @ idle and 60-62 @ 6500 RPM.

I run 6.5 quarts in my GTO pan on a 416.

outkast6991

iTrader: (34)

is it possible the converter is ballooning and pushing on the crank? wouldn't hurt to check the endplay

WKMCD

iTrader: (2)

I run 15w50 M1 in my 427 and don't have those issues.

6.0monsta

iTrader: (7)

The max pressure I'm seeing is ~50. It's less than the 10psi per 1000rpm rule. I'm definately going to add another 1/2 quart or so. And keep monitoring.

Mine is built lose for nitrous. So the lose bearing clearances make for less pressure. Do you actually log your car and take it to the track?