So my oil pressure is really high. 45-50 psi at hot idle with 5w30 Amsoil Signature. Turns out the Melling Shark Tooth "standard volume, standard pressure" pump comes with the "high pressure" spring installed. The normal pressure spring is in the little plastic bag in the box. My assumption is that they do this because of all the poor quality rebuilds that are a natural part of the current SBC landscape and with the high pressure spring it is likely to result in fewer tech support calls about how their pumps suck and the customer has no oil pressure....

Anyway the crappy Summit Racing pan leaks because the fitment is horrible, the drain plug design absolutely sucks, and the firment is such that it is impossible to remove the pan with the engine cradle in place. So today this happened:



I decided I really want the ability to pull my oil pan at any time so an UMI K-member and control arms are on order. And a stock GM Performance pan and gasket are ready to go in.

The engine makes near 400 HP (325 at the wheels) and is in no obvious distress with the high oil pressure. But I'm already here, and I can easily swap the spring now. I figure it might free up a few HP.

Engine break-in has been exceptionally clean. This is maybe 500 miles on the new engine:



GD

 

What were you seeing for oil pressure hot at cruise RPM?

 

Way off the gauge. More than 60. When I tested it on the engine stand with a drill it was over 75. The "normal" pressure spring is suppose drop it by about 15 psi.

GD

 

That does seem a bit unnecessarily extreme... I like high oil pressure and all that, but there's no sense in stressing out the distributor gear and all the problems that go with that, if it's not needed.

The standard pressure spring should be fine.

 

I also agree that, with your level of detail, the stock spring should be fine. I would also check the oil pump pickup location with any new, heck even with a good used pan, and ensure that the pickup tube was installed with enough clearance. also, don't make a mistake like I have and forget that you measured with the pan gasket attached. I thought "it's a little tight, but the pan gasket should add 0.100 of an inch or so. Needless to say, it did not.

 

Good point. I will absolutely measure the depth of the new pan compared to the old pan. I hope it's still right...... I tack welded the pickup tube to the pump

GD

 

Sounds like we have the same oil pump and I see pretty much the same oil pressures. I also left the included spring in. I have Intellitronix gauges that go up to 99 PSI and I've spot checked it against a mechanical gauge, but not while driving, and it's within 5 PSI.

I'm not sure I see how the 60 PSI spring would do much to change pressure above or below the spring's bypass pressure. I see 75-80 PSI cold at a 1900 RPM cruise and it will just barely settle to 70 PSI once everything is up to temp with Redline 10w30. I have tried a step up and step down in oil weight (with some cheaper stuff) and didn't really see a worthwhile drop except when I went all the way down to 5w20. If it's already exceeding the bypass pressure now, it will still exceed it with the lower pressure spring. Seems like a larger bypass hole is needed.

Thing is though, I think this engine had similar oil pressure with a standard M55 pump as well. At the time, I only had the stock 60 PSI gauge so I couldn't tell for sure, but it never really dropped below 45 PSI then either.

I am curious what you find though.

 

Interesting observations. I swapped out the spring and have put the new GM performance pan on.... I am waiting on the UMI K-member to get it fired back up and driving.

The instructions mention that the "normal" spring will not effect the idle pressure (as this is below the spring set point) but will drop the cruise pressure about 15 psi.

GD

 

I guess I'll be the one to ask... Are we certain the cam bearings are properly oriented? The positioning of the oil holes and placement of bearings can be critical to permit oil flow.

 

Yes the cam bearings were installed with great care to orientation, clearance, etc. And being a stock block with priority cam oiling I would think it would be in some distress somewhere if flow volume was a problem downstream of the cam bearings. Especially at 6500 rpm and 400 hp.

GD

 

EVERYTHING can be a problem at 6500 RPM!

 

Yes, but there is nothing like the sound of a SBC at 8000+ rpm.

 

Well I'm not running it to 6500 regularly. I did on the dyno but the governor in the trans shifts way before that so in normal driving I only take it to about 5500 since HP peaks at 5100.

GD

 

I used to get 100 psi on my 396 when it was first started, but I knew that it had a little larger bearing clearances (.0035) on the rods and mains. When it was fully warmed up it had 20 at idle but would jump to 50+ when you cracked the throttle. That was with an M77HV pump with the standard spring. Most of my LS powered trucks always ran right at 65 psi no matter what the oil temp.

I agree your distributor gear will likely appreciate the lower pressure. I've started taking a scribe and putting a line down the side of the lower area on the distributor housing, to create a little leak that will oil the distributor gears. Doesn't take much of a line to get the job done. The critical part is being able to calculate where you need to put the line... LOL! Has to be aimed at the gears.

 

Here is the pic. Groove is .030" x .030"

 

That would be one of my earliest recollections of becoming a bona fide gearhead. Can Am at Mosport Park mid 70's. While those were the vaunted ZL1 427's , that sound has stuck with me forever. In subsequent years it was Formula 5000 with 5.0 litre small blocks making 500 bhp at 8000. Weeeee....

 

I changed out the spring, and the new pan is fitted. I did have to modify the pan a little with some clearance bumps for the Vortec main cap bolts with their splash shield mounting studs.....





The pan was clearanced to fit flush against the block without the gasket so with the gasket there won't anything touching the pan. And I did check that the pickup tube is appropriately positioned.

GD