# Low Oil Pressure 389 (15 Psi)



## dakuhns (Nov 13, 2008)

Rebuilt 66 389 with all new parts bored .60 NEW OIL PUMP
Tolerances in the mains are correct Installed Crower 60916 cam with their new lifters that are shaved on one side to get more oil to lobes....
Why the low oil pressure reading at idle? 
(Pressure goes to 60-65 psi when fuel is applied)


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## dakuhns (Nov 13, 2008)

New Oil Pump shot?


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## geeteeohguy (Feb 2, 2008)

Cam Bearing clearances? Rod clearances? All oil galley plugs installed, even the one at the rear on the pass side behind the "freeze" plug? 65psi at throttle isn't TOO bad. Rule of thumb is 10psi for every 1000 rpm, so you're not in danger yet.....


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## Rukee (Feb 8, 2007)

Is this the break-in oil? If so how many miles/hours are on it? What weight is it? Is it synthetic? Do you have an electric gauge or a mechanical one?


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## dakuhns (Nov 13, 2008)

Rotella deisel oil 15W? Something like that. My buddy who built it said all clearances and plugs in place. Correction..PSI goes to 80 ish not 60PSI as previously mentioned.
Engine is running outside the car on a rig he made...mechanical gauge..changed twice.
He's thinking a valvel spring hung up in the oil pump or a clog...


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## dakuhns (Nov 13, 2008)

Ran the engine two hours total since last Saturday. 3/27


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## likethat (Oct 5, 2007)

I would have used 30w oil for the break in. Some say to not oil the cylinder walls so the rings seat. Some say oil them. Either way I feel that to heavy of oil on break in isn't the way to go. Heavy oil is for broke in engines that are in high heat environments. 20 to 60 psi is good pressure for most engines.


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## 66tempestGT (Nov 28, 2009)

15w is not as heavy as 30w


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## Eric Animal (Oct 28, 2007)

15 at 700 rpms is OK.....more than 80 could cause problems. I'd rather see 20 at idle and 65 at 5000.....


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## likethat (Oct 5, 2007)

Yes but he posted 15w? I am guessing 15w50:willy:


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## Too Many Projects (Nov 15, 2008)

The shaved lifters are throwing a red flag for me. Any additional clearance around the lifter body to let oil drop out of the bore will decrease pressure down the line. It appears to be working fine at rpm but at idle, the pump can't keep up. If the idea of more oil on the cam lobe is to prevent galling from no-zinc oil, I have reservations about it's success. And don't think using a diesel oil will protect you either. All the additives have been removed from them too. You need to run something like ZDDP at ALL times to protect a flat tappet cam.
Try setting the idle up 100-150 rpm and see if it will hold at least 20lbs.


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## 66tempestGT (Nov 28, 2009)

the shaved lifter is shady to me too. but having said that i dont have a problem with 15# at idle.


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## Rukee (Feb 8, 2007)

I think the rotalla deisel oil has the zppd in it already.
I missed the part of the shaved lifter, exactly what and where is the lifter shaved?


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## 68greengoat (Sep 15, 2005)

Rotella is supposed to be loaded with ZDDP. That's what I'm using this year... Although TMP is a trucker, maybe he has the inside scoop and the additive is now gone there too.....:willy:
BTW, I'm running 30 and 60psi......


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## jonnycolfax (Dec 20, 2012)

I have a very similar situation. I just got my 64 GTO back from the shop and the oil pressure is really low - idiot light and auxiliary pressure gauge is bottomed out on idle and only pushing about 35-40 at 3K rpm. It was better than this (yet not good) prior to the work. It was about 9-10 on the gauge and no light at idle and about 50 at 3K rpm. I took it into my shop because of a pretty vicious knock and learned that some oil leakage (or burn-off) had gotten ahead of me. It was low, down to less than 2 qts. Yes, I was embarrassed but in my defense, oil had been changed within the past 6 months without a lot of driving and the pressure didn't raise a red flag. There was also a serious timing problem due to distributor issues that was the primary source of the noise. 

I had the distributor replaced and the shop also replaced all the oil with Rotella. It is full now, even though the pressure is really low. 

The specialist also felt like the engine - all the critical stuff was getting to be end of life, i.e. cylinder and crank shaft wear has created some play, so I am looking at a bigger fish to fry - maybe a rebuild/overhaul. I can't do that right now due to costs. I still would expect that with fresh, appropriate oil and my timing situation addressed, I'd be getting better pressure - or at least the pressure I was getting before the work was done.

I suspect that running low on oil increased the particulates in the system and perhaps a change of the oil filter is in order. I also saw in another thread a recommendation to change the oil again to eliminate any residue broken free from the work done. 

My questions: Am I on the right track with the filter change? - and if I change the oil again, which is new and the expensive stuff (hate to just toss it), can I add the oil back in either after filtering or after letting any residues settle? If I need to pre-filter it, what can I use ... something as simple as coffee filters? Or something more specialized?


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## Too Many Projects (Nov 15, 2008)

68greengoat said:


> Rotella is supposed to be loaded with ZDDP. That's what I'm using this year... Although TMP is a trucker, maybe he has the inside scoop and the additive is now gone there too.....:willy:
> BTW, I'm running 30 and 60psi......


Back in 2010, the additives were still adequate but since then they have been reduced to near nothing too.



jonnycolfax said:


> I have a very similar situation. I just got my 64 GTO back from the shop and the oil pressure is really low - idiot light and auxiliary pressure gauge is bottomed out on idle and only pushing about 35-40 at 3K rpm. It was better than this (yet not good) prior to the work. It was about 9-10 on the gauge and no light at idle and about 50 at 3K rpm. I took it into my shop because of a pretty vicious knock and learned that some oil leakage (or burn-off) had gotten ahead of me. It was low, down to less than 2 qts. Yes, I was embarrassed but in my defense, oil had been changed within the past 6 months without a lot of driving and the pressure didn't raise a red flag. There was also a serious timing problem due to distributor issues that was the primary source of the noise.
> 
> I had the distributor replaced and the shop also replaced all the oil with Rotella. It is full now, even though the pressure is really low.
> 
> ...


Did you change the oil or a shop. If a shop, I can't believe they wouldn't have changed the filter at the same time. 

As for the continued low pressure, with less than 2 quarts you most likely scored the bearings worse than they were and have more clearance on them now, which will reduce the pressure to what you have. I wouldn't recommend running it anymore than absolutely necessary to move it around your yard or shop. You risk spinning a bearing and possibly destroying the block and/or crankshaft.


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## jonnycolfax (Dec 20, 2012)

The shop changed the oil. I'll need to check and see if they replaced the filter. It should be itemized on my invoice if they did. I don't have it handy.

I was definitely hoping for something less severe. It didn't run a lot with the low oil but I am not sure how much it would take on that engine to do serious damage. Is it even worth going in to replace the bearings without going forward with a complete overhaul?


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## geeteeohguy (Feb 2, 2008)

I agree, strongly. Your engine was tired to begin with, but running it 4 quarts low on oil damaged it. You ran it low enough to cause bearing knocking. That isn't reversible. Oil serves as a lubricant and a coolant. My bet is damaged bearings, and very likely scored cylinder walls, as well. No amount of filter changing is going to help. I would not run/operate the vehicle until you can do an overhaul, if you're interested in keeping this engine intact. With ANY old car, driven or not, ALWAYS check the fluid levels before driving if it's been sitting. Years ago, I blew up a rear end in a GTO of mine that had been sitting....and had leaked out all of its gear oil, unbeknownst to me. It only takes a little time to do a "walk-around". Good luck with it.


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## geeteeohguy (Feb 2, 2008)

To your latest post, no, it isn't. Nothing will be with tolerance and you'll have an unhappy, undependable engine. The crank and block will need machining to make things right. But then they'll be right and stay right for a long, long time.


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## jonnycolfax (Dec 20, 2012)

OK. Sounds like it gets garaged until I can deal with the overhaul. My only dilemma right now is that I drove it to work. I can stay off the interstate and keep it slow. It's about 5 miles home. I wasn't getting much noise on the way to work. I think I'll be OK getting back but yeah, you have me really worried. Thanks for the info. "Tired" is exactly the word the mechanic used to describe the engine. 

Engine replacement is another option. I am not sure if this engine is original to the car but I suspect it is. I need to check with my dad-in-law and review the restoration records. I want to keep it as original as possible but if replacement is a better option, surely feel free to weigh in an opinion on that.


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## geeteeohguy (Feb 2, 2008)

If it's the original engine, by all means keep it. It adds a ton of value to the car. 5 miles will be no problem, IMO. I had to drive one with a rod knock over 50 miles home once. I stayed at 45mph and poured in a can of STP to thicken up the oil before I started my trek. Go easy and you'll be ok. If you post the block code (on front of engine by timing cover), date code (by distributor hole) and block casting number (on passenger side of block by bell housing), we can tell you exactly what engine it is.


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## jonnycolfax (Dec 20, 2012)

Right on. I really appreciate the info. I am a pretty optimistic guy. I'll consider this a new adventure. Who knows, maybe I'll buy a bunch of tools and some good books and try to do the work myself. If it is anything like my home restoration work, it should save me a ton of money. Baptism by fire.


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## Too Many Projects (Nov 15, 2008)

Lots of machine work involved to bring a worn out engine back to life. You could probably do the disassembly and save a little but with no experience with engine assembly, I urge you to let a competent shop or engine builder assemble it and have a warranty. Lots of tolerances need to be checked after the initial machining of the block, crank and heads and this needs to be right or it can have a catastrophic failure that destroys the engine anyway. The engine is like the heart of the car and it isn't something you want a bandaid on...


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## jonnycolfax (Dec 20, 2012)

Yes, it took me all of the short ride home to realize that me doing it was a crazy idea. Thanks for the candor. I think I have some good options here for service as we have a few specialty shops for classics and hot rods. I would totally trust my current shop to do it as restoring cars from junk yard to awesome is what they do, but they are pricey. I have some friends who own classic muscle cars. I can see who they're using. I would bet I could find someone fully capable, who will stand by their work but maybe doesn't have the name recognition of my shop. 

If anyone is in the St. Pete FL area, I'd be open to references.


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## geeteeohguy (Feb 2, 2008)

There is a gentleman on the performance years forum called P-dude who is in Florida and has an excellent rep as a Ponitac engine builder. It's all he does. Another one is in Virginia, but he's absolutely top flight, and he's Jim Lehert at Central Virginia Machine Service. You strike me as a guy who's hitting on all 8 with a fast learning curve, so here's my advice: get the shop manual for the car. A LOT of the labor in an engine job is the removal, clean up, and re-installation. You can easily do this part. I would recommend removing the engine yourself and taking it to a builder. You can pull the heads and intake to make it lighter, but I would leave the pistons/crank in place so you don't damage them. While the engine is getting done, you can clean up, and staighten out the engine compartment, wiring, etc._ Don't_ go hog wild and decide to "go ahead and pull the body off the frame" to clean up the rest of the car. Concentrate on the engine and engine compartment. I've done a few of these, and the 389 I rebuilt 'the right way' in 1981 is still running strong all these years later in my '65 GTO. You shouldn't try to "do it all" in the beginning, but I am confident you can do a LOT of it, and yes, you will save a ton of money. Go for it! Also, we are here to help on this forum, so keep us in mind.


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## jonnycolfax (Dec 20, 2012)

geeteeohguy, thanks a ton for the advice and encouragement. I may try to do some of this. I have a couple friends at work that could help we with the heavy stuff. I'll also consult with my dad-in-law who's done work on it before and restores/repairs old tractors for a living. I used to date a girl whose dad rebuilt engines and I learned some tricks about tagging, marking, and boxing parts to keep everything straight. He'd keep diagrams with all the parts numbered, so he knew which parts came from where, down to ensuring that all the screws went back into the same holes, even for a set that was the same size. I imagine with dad's (and the forum's) help, I can partition the work and determine what I can handle. 

I'll also see if I can find P-dude and drop him a PM.


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## geeteeohguy (Feb 2, 2008)

Excellent....you're going about this in exactly the right way. In my mind, 'right' means well planned and thought out, thrifty, and done right the first time. With a little homework and patience, you can save HUGE amounts of money. And if in doubt about parts placement, a digital camera can be your friend!!!


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## BearGFR (Aug 25, 2008)

Rotella S is 15w40 --- that's what I'm running. 

15 psi at idle is nothing to worry about, as long as we're talking warm engine. 
My car idles at 60-70 cold, but once it gets nice and warm according to the factory gauge I've got about 18-20 at around 900 rpm. Above idle though, it stays right on 60.

Bear


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## rickm (Feb 8, 2012)

high quality non synthetic 10w-40


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