DDP

If any of you remember I had oil pressure problems a while back after an engine rebuild. I changed the OPRV, tightened the crank bolt and changed the oil filter multiple times. I found out that I never sealed the crank girdle with loctite 574. Yeah, I know. So anyways, I finall got around to pulling the engine last week. I tore everything down to the girlde. Checked the bearings, all looked good as they should, being new. Then I sealed up the crank gridle. Checked to see if the pickup tube was cracked and it looked fine. Where exactly would the crack be? I put everything back together, all went well. Today I started it for the first time. Ran great but wouldn't build oil pressure without starting the engine. So I ran it and I got oil pressure. It was slow to build pressure but I finally got 4 bar! I was hopeing for 5 bar but 4 is better than the 2 or 3 bar I had before. Well my joy soon faded after seen the oil pressure drop after the oil warmed up and thinned out. After about 5 min of running at idle the oil pressure was 1-2 bar. Then if I rev'd it to 3k rpms, the oil pressure would hit just under 4 bar. Can someone please help me here. I have tried and tried everything I can think of. The oil pump was fine before the rebuild. Could it have gone bad by sitting for a couple months during the rebuild? Any pressure valves in the head that could mess things up? Why do I have such a hard time with this? TIA.

DDP

Should I try a mechanical gauge for oil pressure?

jacklet

i don't know if this will help i had a bad sending unit once pressure never changed on the gauge I also saw one with the wires on it reversed read errattic. for piece of mind buy a cheap mechanical guage and hook it up to be sure-should only take a few minutes the sender is easy to get to. at least you'll know for sure. best of luck

DDP

Thanks for the reply. I tried another sending unit but I question the wires to the gauge. My gauge shows varying pressure and pressure increase with the rise of rpms.

DDP

Got a link here, Thanks Ski.

http://gallery.rennlist.com/gallery/...l_flow_diagram

Here is my question. How does the oil bypass the oil pump and get to the OPRV? Where does it go? I know the oil gets sucked up the pickup tube, through the oil passage between the crank girdle and the block to the oil pump and the oil pump pushes it through the front of the block to the oil cooler housing. But, according to the diagram in the link, how does the oil get from the pickup to the OPRV without going through the pump, does that happen?

hosrom_951

Derek,
Is the oil pump sitting flush with the block?

DDP

Yes, Sir.

DDP

Anything with the oil cooler that could cause this? The oil cooler is the same one I had in my old engine with good oil pressure so I don't think that's it. But at this point I'm nearly out of ideas. This is what I plan to try for tomorrow (today):

Check crank bolt...again.
Mount mechanical Oil pressure gauage.
Pull oil cooler housing and re-align.

One thing I do question is that I have an 86 block in an 87 car. I am running the 87 pan so I have an oil level sender with the 86 pickup and oil pump. But I am running an 87 oil cooler housing with an 86 OPRV. The reason I chose to use the 87 housing was because at the time it was clean, it looked exactly the same internally as the 86 but...the outside had some structural differences. The 87 looked more reinforced. So that is why I went with that. Also, the diff in the OPRVs is fitment in the block, not the housing. I am going to try switching the 87 housing out for the 86 as soon as I can get my hands on an 86. (kinda gave my old one away) Feel free to throw any suggestions at me, positivie suggestions please.

Ski

you have the 86 3 pc or the updated 1(actually two) pc OPRV? There is a small relief valve in the head, allen with ball and spring - been a long time since a took one out.

What oil are you using, 30wt dino for fire it up?

hosrom_951

Not sure on the oil pan, but i am leaning towards the oil cooler. I could be wrong, but if you went for the 87 oil cooler, you should have used the same OPRV that came off it. Since it is an 86 block, i have a funny feeling that by using the 86 cooler with the 86 OPRV the oil pressure problem will be solved.

Again, i could be wrong, but i believe it is best to stick the original parts back in that block.

Imo000

The factory gages are not accurate. Hook up a mechanical gage and check the pressure. If the pressure is ok, then it's either the sending unit or the gage.

Tom M'Guinn

Yes. If you added 1 bar to your readings across the board, they would be in the range of normal.

Have you tried a new OPRV?

Did you seal the pump to the block?

9five1

I think that is only on the S2 or am I totally off base?

Ski

No, mine has one as the spare head in the garage, it's just been a while since I took one apart.

KuHL 951

The 86 OPRV will not work in an 87 housing...different lengths and diameters on the OPRV. They need to match for sure. I think finding an 86 housing would be cheaper than sourcing an 87 OPRV. Hope you find your problem.