When I start the car, i have about 30psi of oil pressure. If i rev it up, the pressure drops, as i start driving the pressure drops and drops, till it gets to 0, and never goes back up.

I am running a mechanical oil guage, so no electrical sender problem.

i have had a blow by problem, and had to replace the PCV setup, with a two large baffle valve cover breather steup like what are on circle track cars. The problem seemed to start after I did this, but I can't think of any reason why that would affect it at all.

The oil pressure is taken from the stand port, at the back of the block next to the dizzy.

I would love some ideas on this.

 

I would swear that the oil pump pickup screen is clogged or the pickup has come off of the pump.
Only engine I ever pulled down that did what you say, had a pickup screen that was coated solid with that brown stuff you see on rocker arms in a high mileage engine. Too many times this important part is overlooked during a rebuild and it is just stuck onto a new pump. Only other thing I can think of is a lifter that has failed and is bleeding oil pressure when it heats up.

 

The engine is fresh off a new rebuild. It now has around 500miles on it. I have had a lifter noise since I fired it up. I just can;t think of why the oil pressure would do that. I obviously have pressure cause I've beat on it many times, and it runs like a top.

Is there any where else on the motor I could plug in a pressure gauge that may give me a reading?

 

run the car until the pressure drops to zero, then pop off a valve cover. as long as you are running a hydraulic cam, you should be getting oil coming out of the pushrods. if you dont, shut it down immediately, cuz you have a major problem.

 

If you truly have zero oil pressure, the engine should be making all kinds of "I'm not happy" noises. I would start by trying another mechanical gauge and line. The gauge might have some crap in it from the rebuild (assembly lube, crud, whatever), or it may have just gone bad.

 

Sure is. And it's more convienient too. Every small block 55-88+ has a 1/8" pipe plug just above the timing chain cover slightly on the passenger side. Use a 2" nipple to get it out in the daylight.

 

Older blocks...
(and I even know what it was used for)

 

Cool, thanks.

By the way, it is a new 2nd guage and new line, cause i thought it was the guage opriginally.

So you figure when everything warms up, and i read 0psi, if i pull off the valve cover, and no oil is coming to the top, then it would have something to do qwith the oil pump, pickup possibly?

Could my dual large breather assembly have anything to do with oil pressure dropping due to excessive venting?

 

What weight oil are you running? sounds like its too thin, Once it warms up it just blows right past the bearings.

Who did the rebuild on the engine?

 

It could. But you would have to have tons of blowby from wrong size rings/excessive gap AND restricted drainback from the topside. If you pulled a valve cover when it was hot lots of oil would come pouring out. I have seen this once before, but the topside was slam full of sludge and the complaint was it took to long to put oil in the engine at oil change.

 

I run a dual breather setup on my 350 and have excellent oil pressure, i highly doubt its your problem.

 

My current oil weight is 20w50, so it's not too thin.

Ihad a performance place rebuid the motor. the motor only had about 1000miles on it at the time, but I had it all pulled apart again and balanced cause it shook alot. The cylinder walls didn't need to be touched because they said they could still see the fresh hone marks, only thing I'm scepticle about is that they reused the rings, but they said it was fine cause there was pretty much no miles on the motor yet.

 

That paints a pretty different picture. Did the same people build it the first time?
Speaking of oil pressure, I'd like to ask the group what is your normal oil pressure hot, at idle (900), with "normal" 10W30? The oil pressure specs always say "operating temp at 2000 rpm".

 

The stock 305 in my TA with 150,000 miles carries 45 psi at idle warm with 10W30 and 60+ (off the gauge) at higher RPM

My 383 in my '90 carries 38psi warm @ 900 RPM and 70psi at WOT with Royal Purple Racing 21 which is close to a 5W30. That's with roughly .0025" clearance on the bearings.

As far as your motor, I would check the pickup to pan clearance. You should see about 3/8". This 'should' have been done by the builder but many skip this step. Too low and it will starve the pump for oil as it creates a vortex in the pan. This will also tend to cavitate the oil causing a drop in pressure. Too high and as the RPM's increase the level of oil will drop and the pickup wont be submerged anymore. This is more obvious with high volume pumps. Both cases will cause a drop in oil pressure in relation to RPM's.

 

Everything was running A1, until I did this breather setup, Ihad 30psi warm, and 50psi at wot. then I did this breather setup and it seems since I did that it started this crap.

 

so take it off and see what happens if you really think that is it....

 

yeah do that for sure.

 

If I go WOT without the dual breather setup, it pops the rear intake seal instrantly, and pukes oil all over the back of the block.

I know I have serious blowby, but since it isn't burning any oil, I'd love to fix this problem, and have the oil pressure reading under control, without having to pull the motor and re-ring the short block.

 

IMHO you have not one, but two good reasons that you will have to pull that engine back out. (especially if you have money invested in it).
1. If you have verified less than 5psi oil pressure the least it can be is an oil pump related problem, (more likely incorrect clearances or something coming loose like a main cap).
2. The blowby is not gonna heal. I have had 2 engines that had bad blowby (both old) and both eventually burned a piston.

Bite the bullet and don't let the hard work and money go up in smoke.

 

...it also has no oil pressure when you drive it, serious blowby,etc etc etc. Your engine has serious problems. It's time to pull it and look for a new machine shop.

 

I've had this problem before. It was a mis aligned main cap. Clearance wasn't checked. Had oil pressure when oil was cold and thick but as it warmed up and thinned out the pressure blead past the cap/bearing and oil pressure gradually fell. I never lost all oil pressure but it started at 50 and dropped to 5 before I always shut it off. If I drove it EASY it didn't drop as quick. If I got on it it dropped alot faster. In this case it was a BBC just thrown together to get to a super chevy show and it was a main cap NOT for this block. Car started the 1/4 at 35 PSI and finished at about 6!! Ran 11.23 @ 123! Your motor may have a main on backwards or the clearances just aren't right. In the end, as posted above, you gotta pull the motor before you wreck a bunch of stuff!

 

I'm having a crazy problem with my oil pressure also It starts out at 80 and as it warms up and you put it reverse or drive it drops and drops slowly until it gets to just before the first red mark but the engine runs very smooth , it doesn't seem to act up unless you are driving it Because I've let it run in the driveway for an hour or better and never act up even thou the pressure drops . I took it out the other day and the pressure only got down to 40 and it ran great but backed in the driveway and even thou it had a 40 oil pressure it started idling up and down roughly . the thing that puzzles me the most is the engine runs so smooth and the oil is clean I even cut open the last oil filter to see if there was any metal flex's or metallic look to the oil and there's not any , and I've replaced everything that's supposed to affect the gauge