SBC low oil pressure

I'm running a 327 chevy motor and I have low oil pressure. (like 5-10 lbs)Engine was rebuilt about 7500 miles ago.Any ideas on why so low?

 

is the low oil pressure a recent thing? or has it always been low?

 

Has it been this way since the rebuild?

 

It was OK and then started slowly dropping

 

Who did the rebuild?
Was the rod and main bearing clearanced set correctly? It should be at .0022-.0025"

 

Dont know.Bought the car a few years ago.It was fine but the rockers were starting to click a little and thats when I noticed the oil perssure.

 

Can you tell us more about the rebuild? Did you do it or someone you trust? Some people tell you it's rebuilt but they only put new rings and bearing in it. Maybe the oil pump, maybe that the block wasn't clean properly and a chunck of dunk is blocking the oil passage. Maybe a sending unit too. Lets here more about it.

 

I'm going to drop the pan to see if some junk is blocking the pump screen but how can you tell if the pump is OK?

 

Take out the sending unit and install a pressure gauge. Check the specs for your motor to find the PSI at what RPM.

 

also change the oil and filter and see how they look....

 

Good idea.I was wondering if it could be the sending unit but the clicking rockers made me think it was more it is low pressure.

 

Going to drop the pan anyway and take a look see.

 

Might be cam bearings if not replaced or damaged at assy.

 

It may be cam bearings as previously said. Pull the pan and check the clearances. If not bad get a high pressure pump and replace the old one. This should increase the pressure if you don't find another problem.

 

If you haven't changed the oil and filter yet, do that first and see how it works.

might fix it.

 

I decided to change the oil it for the hell of it.The oil pressure went back uo to 50-60lbs.How come?Thanks for all of the input guys.It's great to have a place like the HAMB.

 

If the filter has a bunch a trash in it, it reduces the flow.

 

My '64 daily has a 350ci and always has low pressure. Changed oil/filter with 20w50 and gained about 5-10psi, but still not up to par. I'm going to limp this one by hopefully until I get a GM Crate Motor after my tax return.

 

I have the same problem with the 383 in my Nova. I'll have great oil pressure for a month or so and then it will get really low.. Change the oil and put on a new filter and its back up to normal again.. This is on a brand new engine. My header is really close to the oil filter and I"m thinking its heating up the filter and damaging it somehow.. Is that possible ?

 

What brand of filter are you using?


jerry

 

I've been using Fram Filters. What do you suggest ?

 

Maybe the filter bypass is opening from too much flow.....and failing open.

 

There was a link awhile back to a guy that did oil filter testing as a project.

His study showed FRAM as being the worst one. Can't remember the best, but the study reinforced that AC/Delco filters were good ones.

Also, cut the filter can open and cut the paper out with a knife.

Spread the filter paper out on some newspaper and see if there's any significant "stuff" to be seen. Minor traces, especially for a new engine are normal. A bunch is not.

I've saved engines doing this. Sometimes ya' can ID the piece and zero in on a problem before it goes BOOM. One example was a piece of rocker arm. Needed longer push rods to correct rocker arm geometry.

 

I've not trusted Fram for ANYTING in about 15 years. used to have thew same problem youtr having. I've used both AC/Delco or Wix since then and avoided it. The above brands seenm to be much better constructed when cut apart.


jerry