Low oil pressure

[Daygoslow]

Looking for any advice/direction before I pull the engine (even though I know I am going to have to)

I have a primarily street driven procharged 422 sbc. 9.2:1, pump gas, non intercooled (water meth inj) all forged internals and approx. 1500 miles on it.

Oil pressure used to be 25-30psi cold idle @950 and then 12-15psi hot idle 850-900rpm (in gear)and then quickly increases with rpm. 25-30 psi before 1500rpm. Yesterday on my way to work I noticed oil pressure was low 5-7 psi hot idle and wouldn't climb over 18 by 2000 rpm. Engine seems quiet and no obvious problems or noise. Not low on oil. Added aan extra quart anyway and no change. No other signs of issues with exception of gauge reading.

Hoping it was a faulty sender I verified with a mechanical gauge to be sure. Cold it was still lower than normal but would increase seemingly ormal with rpm.cold snap rev to 2500-3k would touch 70+psi but as soon as engine is hot pressure falls and struggles to increase. I run a wix filter with no bypass and Mobil 1 15w50. Already changed the oil and filter and did not find any obvious metal on drain plug, still have yet to cut open filter.

Advice or suggestions are appreciated.

[user-17438]

Did the lash move at all?

[Daygoslow]

Valvetrain doesn't sound any different that I can tell and I have a pretty good ear but I ave not pulled a valve cover yet to verify.

[Daygoslow]

I didn't think lash could affect oilno pressure but I guess it could indicate a cam bearing issue which could.

[Daygoslow]

Yes it has.

[cgarb]

Get those wrenches clean and ready...sorry, but it sounds like you got problems.

[Daygoslow]

I am prepared for that was just trying to get any kind of a game plan beforehand

[mag2555]

I would have a new pump on hand ( bad pressure spring )if your bearings look / check out good.
You may just get lucky and find some crap holding the bypass valve open and beable to clean things out and reuse the pump.

[Zmechanic]

You ever get around to cutting the filter? See any glitter settled out in the oil you drained?

[cgarb]

I had similar symptoms to that when I lost the main bearings in my 350 Buick some years ago. Oil pressure would start dropping when it's hot, worse and worse. Found flakes in my system 1 filter, so that was the end of that.

[jsgarage]

Had similar symptoms in a Chev Z-28 when the flex-drive fan blew, allowing the fan to move fwd into the radiator and core it like an apple. Unfortunately it was during a torrential rainstorm so the young driver didn't notice the engine temp going to the moon. Eventually the engine seized which got his attention. Surprisingly when it cooled down, the poor thing started on the starter but had low oil pressure. Rod & main bearings were fine and a new hi-pressure pump spring did nothing. Finally pulled the engine & found 5 bad cam bearings. Replaced those and magically, oil pressure returned to normal.

[Daygoslow]

No I still haven't cut the filter open yet. I didnt seem to have any metal flakes that i could tell and I had the normal miniscule amount of stuff on the end of my magnetic drain plug. I also run two filter mags on my filter so hopefuly if there was anything that's where it is.

Just really keep feeling this is so premature for this build but who knows.

In talking to some friends still looking for a reason a couple have made mention to me that the catastrophic transmission failure I had last summer could have possibly damaged the rear main bearing, which I didn't think about.

I have been around this stuff my whole like and still had to learn the hard way not to shift a Turbo 400 into neutral at high rpm. Had just made my first (and last since) 7000 rpm dyno pull and lifted and then clicked into neutral to let the rpm fall as the drums stopped the rear wheels. A half second later pieces of that th400 exited and came through my floorpan, my dash and a/c box etc. And fortunately not me.

Engine seemed fine afterwards but I didn't think about that it could have been damaged. I have only had it back together about 2 months now and put approximately 1000 miles on it when this started. Been working some very long hours the last few months and haven't made time to mess with it much this week other that continue to stress over what could have happened.

Need to get that filter cut open and also checked the endplay at the balancer which wouldn't take long.

I understand what the thrust on the rear main bearing does and how to set it up but could a wiped out thrust affect oil pressure this much?

[lg1969]

I had a similar problem where the oil pressure was as 5 to 10 psi on my sbc. It happen to my 307 and recently my 406 sbc. In both cases it turn out be a bad distributor housing. I did not have a good seal for the lifter oil passage. I rebuilt both engine and still low oil pressure. I replace the distributor and oil pressure jumped to 60 psi. 25 psi when it is idling. It drove me nuts.

[Daygoslow]

Thanks. That's one i hadn't thought about

[gottago]

Wondering how common is that distributer / oil pressure issue with sbc? Twice now had to replace new aftermarket dizzy with the stock unit to restore pressure in rebuilt engine.