Reply With QuoteSimple, 50 WT RACING OIL, brand really doesn't matter, 50 WT RACING OIL, this isn't you father's Oldsmobile, or T Bird, 50 WT RACING OIL..............RACING OIL, 50 WT, will also work.....MP
Well, my repaired 460 is running fantastic. Thanks to you guys and this forum. I took out the boat two different times so far.
My other posts tells my story but to make it short I replaced my ruined cam with the same one, new lifters, rod/main bearings(plastigaged at .0025 rod and .003 mains), and a melling stock oil pump. I have a 10qt rear pickup Milodon oil pan. Running a small Ford type Napa/wix oil filter.
Now I'm wondering what's going on with my oil pressure. It stays around 45-50lbs hot up to 3400 rpms when I edge up to around 3800 it drops to around 40lbs. And maybe drops a little more up to 4500 or so. 800 rpm Idles at 20 hot and 75 cold. What's really weird is if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50. It's like it does the opposite of what you would expect.
I'm using 20w-50 valvoline as suggested by many others. The Milodon oil pickup is a good 3/8" off the bottom. And it has a small bracket welded to it about 1/4" off the botton to keep it from sucking pan. The only thing I can think of is maybe the Milodon pickup tube opening too small (about 1-.3/4""x2-1/2).
Could you guys, once again, give me some advice.
Simple, 50 WT RACING OIL, brand really doesn't matter, 50 WT RACING OIL, this isn't you father's Oldsmobile, or T Bird, 50 WT RACING OIL..............RACING OIL, 50 WT, will also work.....MP
With those clearances, and their good...your fine with a straight wt oil. Like money said 50 wt is a good choice. Personally I use Kendall 40 with a touch of Lucas.
The one time I tryed 20/50 it turned into water...noisy lifters after a hard run and somewhat lower pressure.
Are you saying going from 20/50 to straight 50 is going to solve my oil pressure drop off when I rev it? That's what it does. When I rev on it hard the oil pres drops a little. My oil pressure never did this when I had the stock oil pan and pump running 15w/40. I don't understand.
Originally posted by adsala
What's really weird is if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50. It's like it does the opposite of what you would expect.
This part sounds like a "pan design" problem...oil running away from the pickup. Is there baffles around the pickup in this oil pan? I don't think the multi-vis would cause this.
I agree the straight weight is a better choice though. However on the top end pressure drop, if it the viscosity causing it that is a function of increase oil temp and you would see it gradually, not immediate. Also when you backed out of the throttle with hot oil the pressure would not come back up fast like you're describing. That could also be pan design with the oil not around the pickup on acceleration. When you lose pressure due to thin oil it stays low till the oil cools off throughout the rpm range. Then when cool it comes back up throughout the range. What you're describing sound like more of a supply or clogged filter problem to me.
" My oil pressure never did this when I had the stock oil pan and pump running 15w/40."
Better look at the pan and the pickup for sure.
BBFs have a drain back problem from the heads. It sounds like the running oil level in the pan is low and the p/u is sucking air.
Now we're getting somewhere.
Rex,
Yes, right. The pressure is great at 3400 rpm a constant 50lbs. I guess if I was using straight weight the pressure would be higher. But it would still probably drop with higher rpms.
My oil pan has a baffle near the rear. I think it's about 3-4" from the pan's rear. It does not go all the way across about 2/3 and it has two flappers in it. And they are flapping great. It also has windage tray with three bolts holding it down. The rear part bolts to the top of the rear baffle. Sound ok?
058,
Low oil, been there done that ,but it is acting just like that, sucking air. The pan is rated for 10 qts and I have 11 in it. Any ideas how to prove that it's sucking air? Add more oil? I thought this was more of a problem with HV pumps. Oh ya I got EdelBrock Performer aluminum heads. Cost me a fortune!
Silly question, but is it a jet boat pan? Which way do the baffles swing? The baffles could be keeping the oil out of the pump area, or at least slowing it's return.
I still suspect a pan problem but without seeing the inside of the pan its a tough call.
Whatever you do don't overfill it. That is just about guaranteed to cause pressure problems caused by windage foaming up the oil.
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