Oil viscosity, 10w30 or 20w50 for 390

[rcodecj]

I used straight 30w to break in my engine. Engine was a 68K mile engine with new bearings.
I measured bearing specs before and after new, and all was ok.
I am running the stock oil pump.
When I pre oiled the engine before firing max oil pressure was 45 lbs with a drill and cold oil.
When running I had 30 at idle, 45 max until the motor gets real warmed up then 20-25 at idle and still 45 max.

Now I am changing to a Melling M57hv oil pump.
I'm looking for a bit more oil pressure especially at idle.
My past experience has been when changing from stock to hv that the idle pressure increases some as well as the higher rpm pressure.
With that in mind I would like to know thoughts on which oil viscosity to use.
I want to use either Valvoline racing VV205 10w30  or Valvoline racing VV211 20w50.

If I had not changed oil pumps I would have leaned towards the 20w50, but now with the high volume I am leaning towards 10w30.
Thoughts?


rod bearing clearance was .002
main bearing clearance was .00175
Crankshaft end play is .007
Rod side clearance is .015 to .018

bearing clearance measured with plastigauge 

[afret]

You seem to have plenty of pressure at idle but your max pressure is kinda low.

[Ford428CJ]

My thoughts are this.... If you run the car during Hot summer days out on the street/strip.... 20w-50 is what I would run. All depends on what you are doing with this engine? What are your engine specs?

[rcodecj]

My thoughts are this.... If you run the car during Hot summer days out on the street/strip.... 20w-50 is what I would run. All depends on what you are doing with this engine? What are your engine specs?

1968 390 2V 68k standard bore
new moly plasma rings, rod, main, cam  bearings
Cam Research 226/232 .540/.565 110 lsa cam
Cloyes tru-roller timing chain
Erson rocker shafts and pushrods
Survival Motorsports stage X heads with 2.2” intake and 1.66 exhaust valves
PI intake manifold with thermal barrier coating
428 cj exhaust manifolds
Pro Systems 750 HP double pumper carburetor
Faron recurved distributor

C6 transmission
ATI 2700 rpm torque converter
3.50 traction lock rear gears
Magnaflow 2.5” mandrel bent exhaust with modified stock exhaust tip

I'm in AZ, but I am not here for the summer months. Typical temp in the 70's.
The only thing I have against 20/50 is that on my other car I run 15/50 Mobil 1 synthetic and have an oil temp gauge in the pan.
It takes 6 or 7 miles for the oil temp to come up to its max, oil pressure goes down within a few miles of easy driving.
I feel that I may have more wear in just getting the oil up to temp with 20w50 than I would with the 10w30.
It seems a lot of my driving is testing out something new on the engine, so it gets floored almost every drive. 
That being said, I don't drive it alot but I don't want to spin a bearing either.
When I get things sorted out it won't get as much abuse. 
I pulled a rod bearing to check after 150 miles with the 30w, and it looked good.
I intend to shift around 5800 rpms.

What am I going to do with this engine?
Run it hard every time I get a chance, that meaning taking it up to 5000 to 5800 rpm's in spirited driving.
It is not a race motor and is not in a race car.
I will take it to the track but only when major changes have been made.
I'm not going to beat on the car at the track.

[Ford428CJ]

Whats your oil temp with both oils???

[rcodecj]

Whats your oil temp with both oils???

Sorry, my previous post may have been unclear.
I only ran 15w50 Mobil1 synthetic in my other car with the oil temperature gauge.
I haven't ran that car for around a year, but if I recall correctly it was around 140 degrees.

I will say one thing, once you have an oil temp gauge, it's a lot less tempting to get on your car before the oil is up to temp.
It's kind of a good reminder to wait until the oil is up to temp, which is much longer than just seeing the water temp come up.

[cammerfe]

I believe you are looking for a solution to a non-existent problem. Most likely your hot running pressure will come up from 45 with the addition of the HV pump. Everything else is good to go now. I suggest you use the 10-30, since it will provide better lubrication due to the smaller molecule size.

KS

[Richard F]

This is just my experience.  I have a blueprinted HV pump with a high pressure spring.  I had the best oil pressure when I went with 15w50 mobile 1.  My idle pressure when hot was 10 psi, but when I switched to the 15w50 it picked up to 20 psi in the hot summer months and 25 psi in the winter.  With the high pressure spring pressure was never a problem except at idle.  Unfortunately I can't remember the clearances as I built it in 1998.  I really like the 15w50 mobile 1.

[cammerfe]

Simplified Explanation---supplied to me by a Mecca guru thirty years ago....

The higher the last number in the oil viscosity designator, the larger the molecules of oil. But think of it this way---if you feed marbles, under pressure, through a two inch pipe they'll go right through. But no matter how much pressure you use, you'll not be able to force a baseball through that same pipe, so you have higher pressure but no function.

Both the marbles and the baseball are the little 'ball bearings' of oil and the pipe is the tiny spaces inside your motor. Small molecules support the metal surfaces and keep them from touching each other. Larger molecules can't get in between the metal surfaces properly so they don't provide proper support even though the effort (pressure) is higher.

Always use the lowest viscosity that works for your situation.

KS