Hey guys, I am having the same problem. It has done it since day one and my motor now has 15k hard miles on it.

My hot idle is ~10psi and cold idle is ~70psi. Cruising at 2500RPM is ~40psi. WOT reaches about 50psi, and around that 5k mark it also makes a short dip to ~30psi and then returns back to ~50psi.

My oil pump is also a Melling -standard volume, with GM high pressure white spring. The pickup tube is fully welded on.

With 15k miles of beatings, the pressure characteristics have not seemed to change any. I usually use WIX oil filters but have used others as well. I haven't done an oil analysist, checked with mechanical gauge, or really even looked into solving the problem. I use SuperTech synthetic 10w30 and after 3k miles my oil looks a healthy dark brown with no signs of bearing material.

I am really interested to see what you guys come up with as I'd like to solve the problem myself. I'm no engine expert. It may come apart this winter when I am unable to drive it for awhile

 

Mine is similar and also runs about 50-60 at startup and then slowly goes down as it warms up. The pressure reading goes up and down in relation to rpm. At about a 750 or so rpm idle after it has warmed my pressure is only shown to be at 10-15psi. I'm going to replace the pickup and pump within the next few weeks and I'll post if anything has changed. The car seems to run ok, but seeing the pressure that low is quite terrifying.

 

I have ~30 psi at idle. We are having an issue with the pressure being 60+psi up ~3000 RPM then the pressure starts to drop for some reason at WOT. It then comes back strong a few hundred RPM later. The one thing I've noticed that we all have in common is the white high pressure oil spring. I'm replacing that spring, with the stock pressure spring, to see if it solves the problem. All my old bearing clearances checked out just fine, but due to some kind of trash rolling through my #1 main, at some point, I'm replacing my bearings as well.

This thread is not about low oil pressure in general. The only cure for that issue(to my knowledge) is new bearings to tighten up the clearances.

 

Well, I got the Z back on the road today. I had the chance to get on it for a little just to check and see if I fixed the oil pressure issue......and it's still there.

That is so disheartening after all that work. So here is what I changed just for reference.

• New Main Bearings
• New Rod Bearings
• New Cam Bearings
• New Oil Pump(with standard pressure spring)
• New core plugs
• New oil galley plugs

I stripped the block bare, washed it, rifled brushed all the oil galley passages, etc, etc. All the bearing clearances checked out fine.

Don't get me wrong, I learned some things from the experience, but I'm disappointed that the problem is not fixed. I'm just not sure where to go with this issue now.

I'm going to have to walk away from this thing for a while.....

 

Damn thats just awful.

Ever since I went to a different oil pressure sender I have not seen it. I believe this sender is just less sensitive to quick change.

Might have to put a Milodon pan on it like the other guy did with the problem. He says that fixed. I have decided not to chase it any further because if the motor was going to blow, it would have laready done it.

 

It just drives me nuts that something has changed for it to do this. I used the same type oil pressure sender(GM), pan, pickup depth, etc as I have for years and never had this issue. I just can't buy into the pan as my problem(I'm not fussing or anything, just thinking out loud). I'm just going to drive it for a while to let the bearings mate up to the surfaces and think on it.

Just frustrating....a year's worth of work and not a thing to show for it. Well, except for my rebuilt tranny by Tick Performance in Moorseville, NC. That thing is working well.

Hell, it is just going to be my backup engine anyway. Guess I just need to start saving for a 383 shortblock and getting this spare set of heads ported for it.

This is going to bug me like when you can't remember the name of a song.

 

When you load up the crank, which way does it shift? To the front or rear of the engine?

 

An anti-cavitating oil pump, standard volume, white bypass spring should solve your delimma. Builders had the same issue 10yrs ago when messing with LT1s over at the f-body.org email list(before forums evolved). Moroso(post#26) has them, or like Injineer mentioned there was a web site that showed how to add the a-c 'grooves' to a standard oil pump. The white spring will help maintain full pressure(~60-65) at the high end, since the 'grooves' do releive some of the full pressure potential of the pump.

 

I've been thinking more on this......

.....and if I recall, it seems that my problems may have started after I started using a Fel-Pro pan gasket. I remember taking the car down the track with the CC503, 1.6 rockers, high pressure spring, a stock oil pan gasket, and NEVER had any oil pressure problem. However, the pan gasket started to leak because I used the incorrect sealant on the ends(used Permatex #2 instead of The Right Stuff). When I pulled the engine to correct the leak, I went with a Fel-Pro gasket and sealed the ends with The Right Stuff. That is when I started noticing oil pressure issues. That gasket is thicker than the stock gasket(around 1/8" thicker if I remember) and it may have set the pickup too far from the pan. I may have made the mistake of figuring that the 1/8" greater distance would be okay. The distance of the new pickup is roughly the same as in this thread with pics....

https://www.camaroz28.com/forums/sho...d.php?t=712714




I said in that thread I would set the distance to 3/8", but I did not. I left it stock height.

After I get it inspected, re-registered(can't get registered without an up to date inspection now in NC), and put some easy miles on it(as not to loose pressure).....I will redo this depth to 3/8" and get back to you with the results. This will also give me the chance to check the new bearings after a few hundred miles.

Just for kicks and thrills, how many of you guys, with the pressure problems, are using a Fel-Pro gasket and have not tweaked with the stock pickup height?

That would be some **** if I was the cause of my own problem.

 

I am running the same gasket.

I also ran the pickup at 3/4" (yeah too much) by accident when I flubbed the measurement and it did the same thing. Its now ~3/8" from the pan floor. IMHO, I dont think this is measurement is super critical assuming you are close to 3/8". I also dont understand why all of a sudden the pan is mysteriously inadequate.

Might be worth trying the Moroso anti cav oil pump.

 

Wrd,

I think I'm going to get a Moroso pan/pickup and see if that will solve this problem. I'm going to start pulling the engine this week(got to put in a different clutch disk too).

This is an interesting post. Oldbogie kinda gives you an idea of where are all the oil is when running.
http://www.hotrodders.com/forum/lt1-...ad-117230.html

I guess I didn't realize how little oil is really in the pan at moderate engine speed. The one thing that changes with engine power is rate of engine acceleration. That coupled with slinging the oil to the back of the pan could be our problem. It may be that the rate was borderline stock and making it faster is showing the problem. The only thing that bothers me is why some run fine with the stock pan and others do not.

Based on this....
https://www.camaroz28.com/forums/sho...oso+pan&page=2

I'm going get this Moroso pan and pickup on the way. I would assume that setting the pickup height is a no brainer based on the picture.

This issue has really bothered me. I feel that I can't use the car for what I want to for fear of tearing up the bearings. I really hope this solves the problem.

 

I'm considering hitting the pressure problem with the pan and pump.

Does anyone have this pump on a LT1?

http://www.moroso.com/catalog/catego...?catcode=14444
http://www.summitracing.com/parts/MOR-22101/

When looking at the application on the summit page, it only states Gen I SBC. I'm assuming that it would work on the LT1, but I'd like to know for certain before ordering it.

 

Sounds like the sender... Save yourself some time and replace it the first time with the OEM Sender from Chevy. If you decide to go to Advanced or one of the other auto-parts stores... get the OEM sender the second time a couple of days later.

 

Agreed. Since that last sender, I don't get the negative spike. I still have not verified if the spike is still there using the mechanical guage to really determine if it is still there or miraculously gone.

 

Already done. The new GM one agrees with the old one.