This is pretty much the standard SBC oil pressure issues.

Last year I put my street 6000 rpm max 383 stroker with Comp Cam Extreme Energy roller cam together. The mains ranged from .0028" on 1-4 and .0030" on the rear cap and the rods were .0020". I had to use X bearings on the mains because the original clearance wasn't enough, only in the .0018-.0022 range.

I used a standard Melling M155 oil pump with 3/4" pickup. It is a 1997 block and that is the size that was in there.

Cold start I am getting 50 psi at 700 rpm idle.
Warm 700 rpm idle it is only 12-15 psi. Autometer mechanical gauge- Which I know it technically enough but I get uneasy about it and also don't like the stock gauge showing sitting on 0 while idling. Tap the gas and it shoots up.
This is with 5w30 oil.

I have to take the engine out to reseal the front cover and install a new transmission this spring.

I was thinking when I have it out to install a MELLING 10551ST oil pump - 25% higher volume and 10 psi higher relief spring, but use the spring for stock pressure that comes with it.

For decades there have been arguments for and against a HV oil pump. Usually claims of eating cam or distributor gear teeth.
But with my larger clearances would there be issues?

 

Your bearing clearances are too large to use 5W30 oil. That was never for an old-school SBC.
Modern engines with tighter clearances use those thinner oils.
You have to change the bearings or use thicker oil.
BTW, you can mix and match bearing sets to dial in the clearance you want to achieve.
Even GM did this at the factory. But they did it more to compensate for machining tolerances.
Was your block align honed? You can use a standard size (or undersize) bearing in one half, and a plus or minus .001" other half to dial in half-thousandths.

 

No align hone.

I would rather not change the bearings, but I do have a few sets of STD size. That would bring the mains down to around .0018-.0020. But at the time of assembly I was told that was too tight.

As far as thicker oil, I used to run 15w40 Rotella in some other engines. I could always try that. Or would a 20w50 be in order?

 

What does the pressure do at cruise rpm
and wot? 12-15 at idle hot is plenty

else run a 40 weight

 

I'd start with the Rotella before doing anything else, see how that goes. Did the block get new cam bearings in the recent build? On a cold start after sitting a couple days do you hear any noise (bearing rattle) for a few seconds?

 

As soon as you step on the gas it shoots up and at cruise will be 35 if I remember right. WOT is 40-50.

It got new cam bearings. No noise from a sitting start up.

 

Honestly thats plenty. Probably could do go up in weight, maybe even 10w30 since you likely dont need it that thin for cold temps. I have used rotella in my stuff and like it. Seems to do fine, so can go to a 40 weight.

if you do take it apart and put in the higher volume you will see more pressure, up to the point of the relief spring. Idle pressure may or may not go much higher once hot. I wouldn’t necessarily put a high pressure spring in it. 50 is pretty good.

 

M99HVS and 10w40

My 383 has slightly better clearance and even with 5w20 holds over 30 psi at hot idle.

M99HVS is a big block pump setup for a small block that includes a matching pickup and steel sleeved driveshaft. Big block pump uses less power to spin than a high volume small block pump.