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-   -   Sbc very low oil pressure. Use thicker oil? (http://www.hotrodders.com/forum/sbc-very-low-oil-pressure-use-thicker-oil-228954.html)

bigdog7373 01-29-2013 03:53 PM

Sbc very low oil pressure. Use thicker oil?
 
Hey guys the 350 in my car has very very low oil pressure at hot idle. Cold idle its very good. Hot idle in gear is literally sitting just over 0 on the gauge. In neutral it comes up to like 4 or 5psi, then when cruising it looks ok. Just slightly under 20psi. The annoying thing is that it doesn't have many miles since rebuilt. I was thinking maybe the filter is clogged, but I didn't think that it will affect oil pressure, at least not this much. I was thinking of getting a fresh filter and some thicker oil and seeing what that does for it. What would be a good oil to get? I would think 20w50 is too thick. It has 10w30 in it now. I don't know if 10w40 is a big enough jump to make any difference. Any help is awesome. Thanks

ap72 01-29-2013 04:30 PM

10W40 will make a difference, hell just throwing in 1qt of 60w into what is currently in there will probably bring it up in about 30 seconds. Since its just rebuilt y9ou may be running large clearances and need a thicker oil, just go thick enough to get good idle pressure though (10psi) and leave it at that, too thick of oil can cause other problems too, especially on a street car that can see short trips where the oil doesn't get hot enough.

delawarebill 01-29-2013 04:55 PM

pressure
 
pressure is good but flow is MORE better.. (thats gooder english)
ck the filter for sure. i'd stick with the 10/30. have u ck'd it with a good gage at the dizzy port area ?? there are others on here of more knowledge then me..

LATECH 01-29-2013 04:58 PM

20 psi at cruise is too low. 0 is also too low. chances are it wont last long before :pain:
I would tear it down Dog. Something aint right, and you risk damaging some parts pretty seriously if not taken care of.
A newly built motor should be resting at 40 ish at Idle when warm.

bigdog7373 01-29-2013 05:33 PM

I thought a rebuilt sbc goes by the 10psi per 1000rpm rule.
I can't tear it down either, Im living in a rental house in a community that hates my car. No joke they yell at me for it being too loud and "unsightly". I'm 100% sure they wont be happy if I rip the engine out in my driveway. I'm going to exhaust all my options before I do anything like that. I'll try the heavier oil and new filter first and see how it goes. 10w40 will be enough?
Hopefully that will get it up to an acceptable pressure. If not then Im not sure what I'll do with it. I've been wanting to drop an ls in there for a while now.

LATECH 01-29-2013 05:48 PM

Lots of places like that in florida , so I understand.
10 lbs per 1000 is a general rule.
All of the 350 SBCs I have ever built have carried 40-45 PSI , fully warm on 10w30 at Idle.
Sounds like You have a clearance problem somewhere. JMHO

ap72 01-29-2013 05:48 PM

Instead of swapping out all the oil just add a qt of 60w first and see what happens.

and yes, 10psi per 1000rpm when hot.

Jake_Dragon 01-29-2013 07:00 PM

20w40 in the summer and I have great oil pressure. 50000 miles later I am still running the same oil and have the same oil pressure.

bigdog7373 01-29-2013 07:10 PM

Quote:

Originally Posted by ap72 (Post 1640237)
Instead of swapping out all the oil just add a qt of 60w first and see what happens.

and yes, 10psi per 1000rpm when hot.

Ive been meaning to change it for a few weeks, might as well do it now.
Quote:

Originally Posted by Jake_Dragon (Post 1640258)
20w40 in the summer and I have great oil pressure. 50000 miles later I am still running the same oil and have the same oil pressure.

Thanks. I was gonna try 10w40 with some w60 mixed in and a zinc additive for the flat tappet.

carolinacustoms 01-29-2013 08:04 PM

If I had to take a guess, I'd say someone did not change the cam bearings OR installed them turned wrong (it's easy to do, been there myself), and I also had a guy bring an engine by that was a fresh rebuild with less than 1,000 miles NO oil pressure. The builder (who was supposed to know what he was doing,) did not use any assembly lube. Needless to say the bearings were all junk. But I am completely guessing. I have had good luck with "Hi-tach" and Lucas products for quieting down noises and increasing pressures a bit. I run one or the other in all my high mileage engines, but just my input on it. Either way you most likely have an internal problem and will eventually have to pull the engine, however the thicker oil or additive will buy you sometime. Again ALL of this is JMHO, Best of luck with it :thumbup:

Kelly

vinniekq2 01-29-2013 08:27 PM

I use heavy oil all year.
Just for your information,some of the older BMWs have almost no oil pressure at idle when new.Just the design. what brand of oil filter do you use?

GMCTRUCKS 01-29-2013 08:40 PM

Many of people rebuilt engines but don't do them correct to me building is if the factory would have done with all there specs not just replacing the rings and head work one needs to do all the bearings.

Try Castrol High Mileage oil oh im not saying you didn't do it correct im thinking you had someone do the work for you. Good luck my friend.

Many moons ago a friend of mine rebuilt a 455 HD engine well he had so much blow by he had a water hose atteched to valve cover going under the car that was sad since he had all HD parts he just didn't put it together correct.

bigdog7373 01-29-2013 09:01 PM

Its an stp filter. I run them on all my cars. I don't know how long its been on there though, definitely gonna change it.
I'm not going to doubt that there are large bearing clearances, but the block checked out ok and the cam bearing looked faily new so I left them alone. No blowby or anything. It runs great and no noises. Could the pickup be clogged? Maybe from debris during breakin?

carolinacustoms 01-29-2013 09:18 PM

Quote:

Originally Posted by bigdog7373 (Post 1640306)
Its an stp filter. I run them on all my cars. I don't know how long its been on there though, definitely gonna change it.
I'm not going to doubt that there are large bearing clearances, but the block checked out ok and the cam bearing looked faily new so I left them alone. No blowby or anything. It runs great and no noises. Could the pickup be clogged? Maybe from debris during breakin?


That is a possiblity, not sure break in would have caused enough to clog it, but something may have. And for the record I wasn't saying you built the engine wrong just giving ideas of what may be the cause. After I read my post it did not read the way I intended. Sorry if I came across wrong.

Kelly

lg1969 01-29-2013 09:19 PM

Quote:

Originally Posted by bigdog7373 (Post 1640211)
Hey guys the 350 in my car has very very low oil pressure at hot idle. Cold idle its very good. Hot idle in gear is literally sitting just over 0 on the gauge. In neutral it comes up to like 4 or 5psi, then when cruising it looks ok. Just slightly under 20psi. The annoying thing is that it doesn't have many miles since rebuilt. I was thinking maybe the filter is clogged, but I didn't think that it will affect oil pressure, at least not this much. I was thinking of getting a fresh filter and some thicker oil and seeing what that does for it. What would be a good oil to get? I would think 20w50 is too thick. It has 10w30 in it now. I don't know if 10w40 is a big enough jump to make any difference. Any help is awesome. Thanks

There are two areas you should check. A defective oil pump or the distributor itself. The housing itself may not be sealed causing the oil passage to leak back in the oil pan. I had to replace my distributor twice. Once on a 307 and most resent my 406. Hope this helps ya.


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