I put my new mill on the dyno and at idle I have 75 psi and at WOT it goes to 100 psi. I'm running 15W-40 Rotella T in it so I'm thinking about switching to a 5W-30 or something to get it down. I like the Rotella T but they don't make it in a 5W-30 or maybe I should try a synthetic??? It's a 700 HP small block that spins to 7200 rpm's and used on the strip only. It's in the car already and I don't wanna pull it out to mes with the pressure spring either... Any suggestions are greatly appreciated!!!

Rotella makes a straight 30 and 10w30 oil. Last season I ran the straight 30 and got 80 psi cold and 30 hot at idle. I found 10w30 Rotella this year and just changed my oil with that last week. I am still getting 80 psi cold but hopefully the 10w will help the oil warm up faster. I have also decided to use a bottle of STP with my oil season because I have heard that the zinc levels have also dropped in the Rotella products.

You only have 1 choice left.... thinner oil

JUSTA' thought ....

I remember an article in National Dragster some years back written by WJ .... He ran ZERO weight oil at 50 psi max.

Running the oil pump UP as high as you do costs HOESpower !

Don't forget that what keeps the bearings happy is the "wedge" of oil that separates the journal from the bearing. Too light of an oil mixed with too big of a clearance and you have a rod stuck through the block. Not a good deal. For us do it yourselfers, 20w50 and larger clearances make the most sense. pull the pan and set the pump properly, or run the risk of bearing failure. To ease the process, get a priming rod so you can spin the pump for a test with the pan held with a couple of bolts, then you can put it together the rest of the way when you are happy with the pressure output. A good 3/8 drill will give you full pressure readings.

I and a few others had the same problem last spring when I used a new Melling pump on my SB. 70 at idle and over 100 revving. I switched to 5W20 and it's fine now. Cold idle is 60, hot idle 45, and at speed it's around 70.

I have the same issue with my 408. After break-in, I went with a full synthetic ( 10-30 Royal Purple ) and droped the pressure by about 15 psi accross the board. Pressure is still a little higher than I would like and I'm sure it's costing my some HP, but I have been running it that way for 3 years now with no problems. Remember, after you get some runs on it the pressure will come down a bit also. IMO, people run too high a viscosity oil in general. Todays lubes are a bunch better than years ago.

I've gotten lower oil pressure after switching from higher viscosity break-in oil to thinner race oils. (old 30 or 40w race oils to 5w-20 Amsoil Dominator synthetic) and it's definitely faster, from idle to 1/4 mile. But don't bank on the diesel oils having a lot of zinc, especially if you are running flat tappets. They've been reducing them also and you have to keep checking reliable sources to keep up. But some do advertise extra zinc, which doesn't hurt a race motor either way.

Amsoil high zinc synthetics

Diesel oils have low zinc levels because the trucks now have cats on them just like a car. My last sb race motor a ran 10/30 brad penn and it still had 70 psi cold.

Man you guys need to keep up with the times. I'm running 5W-20 synthetic in my motor. That 20w and 50 weight crap is old, old news.

I think I'm going to try Mobil 1 10W-30 Full Synthetic and see what happens. Thanks for all the info!!!

When I built my 414 with a new Melling pump I had the same issue only much more drastic. The needle on the gage, at WOT, would actually go almost all the way back around to zero! I thought that the gage must have taken a crap so I tried another, but same thing. Switched from the Mobil 1 15/50 to the real thin Royal purple stuff just to see what it would do, and it lost about 20 psi across the board, but still WAY to high. Took the pump out and had my engine guy check it out, even though he had blueprinted, and deburred everything and checked the pressures on his oil pump dyno. Again, it checked fine, all he did was took out the piston and spring, check piston travel, and then lightly hone the piston and bore. I put it back in the motor and again WAY high press? ARG!! So I then just got another Melling pump, had my guy "go over" it and put it in and it was perfect, about 30 psi at idle hot, and 75 at WOT. Why was the other so high? Dunno, but maybe ya just need to try another pump. With the new pump in ET was just over a tenth quicker in the 1/4. Good luck.

Rotella makes a 5-40w synthetic diesel oil!

Ryan,

What are your main and rod clearances? If your a little big on the clearances run a straight weight. I am just in the process of putting my back together and put a oil pan heater and two block heaters in. The engine with most likely be 150 before I fire it LOL!