New Engine: Oil Pressure / Oil Weight Used

DrFishbone

SCCoA Member
My rebuilt (much pain involved) SC engine is in it's break-in stages right now - using cheap 5w-30 oil for the first 100 miles. I installed all new bearings, checked the timing cover for excessive wear, installed new 94-95 Melling oil pump, primed the engine (although I put assembly lube on everything beforehand) So far, I've driven it about 50 miles and have noticed that it after warming up to around 210°F - which I don't like - the oil pressure at idle (around 750rpm) is very low. My Autometer gauge says around 13psi! :eek: Around 1500rpm cruising down the street it's around 25psi and around 2000rpm it's 40psi. The low number at idle is especially disturbing to me with a totally rebuilt engine and stock-weight oil. I need someone to comfort me. :eek: Upon startup, while the oil is near ambient temps, the pressure will sit at and stay at 60 psi, only when the engine temp gets rather warm does it drop so low. I'm thiniking of using something like 10w-40 for the next 400 miles of break-in to help keep the pressure up. Any comments / experience / input on a similiar situation anyone has had? Experienced advice is very welcome!

My old engine with the same Autometer gauge & sender would read 60psi at startup, then at the lowest would read 20psi at idle but that motor had 265k miles on it! :rolleyes: If nothing else....are these numbers safe? I'm sure that they are minimally safe at best.
 
wow, just put a new 94-95 pump in mine with an mechanical autometer gauge and I idle is 70 psi and only goes down to about 45-50 when it gets hot down here in Florida. I running dino 20-50 for the next few miles and then go back to 20-50 mobile 1. I do have a stock lower end with 98 K on it.

Mine runs up to about 209 or so with the air on and in traffic.
 
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just as another reference, I cold idle at about 53psi, and hot idle (190deg) at around 37psi. My engine is a stock bottom end though, with 110k on it. Did you properly check your clearances with the new bearings?

::EDIT:: With 5w-30 synthetic my readings were roughly 25psi hot idle, 50psi cold idle. With 20w-50, the readings are as shown above.
 
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You guys are probably both running 50 weights, he is running a 30wt. I personally think he is probably fine, the rule of thumb is 10psi for every 1000rpms. I think 50wt is a little too heavy, it just creates more pressure because its very thick and doesn't flow as freely, that does not mean it is lubricating parts better. If anything try a 40wt, but remember it IS spec'd for 30 weight oil.
 
You guys are probably both running 50 weights, he is running a 30wt. I personally think he is probably fine, the rule of thumb is 10psi for every 1000rpms. I think 50wt is a little too heavy, it just creates more pressure because its very thick and doesn't flow as freely, that does not mean it is lubricating parts better. If anything try a 40wt, but remember it IS spec'd for 30 weight oil.

These are the same Ford engineers that designed it to run at 220 degrees (or more), have on or off gauges and change the head gaskets everything you change the plugs, also spec's out the 30wt.:D:D Think I will keep my heavier weight oil. :D
 
Alright, I would say those would have been different engineers but fair enough, I guess. Just especially the cold flow of 50wt oil, I would not be surprised at all if that oil is not flowing everywhere it needs to be while its cold. Have you ever done a UOA to back up your claim that 50wt oil protects better? Or are you just going off oil pressure?
 
If you have bearing wear that supports diesel oil then go for it. I tried 20w50 in my car and the rattle it made woke the neighbours up and I immediately shut down. Went back to 10W30 and the car was whisper quiet and made great oil pressure.

I was seeing 30psi at 700rpm hot idle and 70psi at cruise with 10w30 mobil 1.

Fraser
 
If your engine is making less oil pressure after a rebuild than before, then you have issues. Did you replace the relief valve in the timing cover? I would not be comfortable with the oil pressures you have indicated.

A healthy engine will deliver 30-40psi hot idle and 65-75psi hot cruise (2000rpm and above). If you know what your bearing clearances are that will help you to determine the correct oil to run, but as a general rule I suggest whatever oil weight is necessary to achieve the above listed #'s.

If your motor has a few hard miles on it, the clearances will be wider allowing (or more appropriately asking) you to run a heavier oil. I would not run 20w50 on any street car personally, but I guess if you live in a really hot climate it might be tolerable. Absolutely out of the question in the north.

I have noticed that Mobil 1 now has a 0w40 oil that is recommended for high output and supercharged overhead cam motors. This might be a decent oil for the SC.
 
Did you replace the relief valve in the timing cover?

There was one of my concerns - I forgot to change it until I already most everything together :rolleyes: Would the pressure hold at 60psi when cold though?

Did you properly check your clearances with the new bearings?

And there was my other concern... When I put the new bearings in, I 1) didn't "know better" - in other words didn't think it was imperative at the time and 2) didn't know where I could get plastigage anyways. That was one of the few things that's been on my mind ever since putting the oil pan on about a year ago.

So, there's the two possible problems that could've been ruled out had I decided to take a few steps back. :(:rolleyes:

So the question is, where to go from here. Try some 10w40 oil? Or even 0W40? Is it possible that the cheap break-in oil I bought (being the Supertech Brand) thins out more than it's rated to? I'm thinking it's more likely a problem with my workmanship...after all I went through. :rolleyes:

The car runs really well...the only odd thing that it does is a "chug chug chug" feeling when decelerating at about 1750rpm or lower, especially downhill. This is not related to oil pressure - it always does this. Accelerates very nicely, idles steady except for cam "lope". AFR is around 15-14.5 at idle and gradually goes down to around 13-12 at 3500rpm which is as fast as the engine has been run so far.

Anyways, back to the oil pressure...:rolleyes:
 
personally, I would pull the motor and properly set up the bearing clearances. Plastigauge can typically be found at NAPA, or at this point, you can get it many places online. Dave is the expert on these motors and has the knowledge of what clearances are ideal and has the eye to spot problems.

I think you can get away with running a heavier weight oil, but I think it's just masking the problem and its only going to get worse with additional bearing wear.

I personally run 20w-50, only because I was looking to generate the above mentioned oil pressures( I get 30ish psi hot idle, 50ish psi hot cruise). My motor is bone stock on the bottom end with 110k so my clearances are less than ideal plus I have the original pressure relief valve that could at this point be weak, and even with the heavier oil I don't see pressures exceeding 55psi even when cold.

I tossed in the heaiver oil just to see if the pressure would go up. It did, but only rose about 5 psi globally. Next oil change I'll switch back to a standard weight oil. I live in the North East, but I only drive the car from late May until September so the ambient temps are at least in the 70's. I def would not use a heavier oil if you plan on driving the car in colder temps. Over the winter I had to pull the oil filter and the small amount of oil that came out was very think due to the temps.

Anyhow, in my case, my pressure isn't ideal, but the engine is tired. In your case, since the bearings are new, I wouldn't feel that your pressures are acceptable.
 
Not replacing the relief valve was a big mistake. There can be debris in there that could cause the valve to hang open. If this is the case the motor will not live long. The other alternative is that the crank was worn more than acceptable limits resulting in excessive clearance on some or all bearings. If it is excessive clearance, a heavier oil will help, as long as they are not too far out of spec, but if it is the relief valve causing issues then a heavier oil will only make matters worse.

The relief valve came with the oil pump and is easy to change. You should never re-use a relief valve. Plastigauge is available at the parts counter where you purchased the bearings for about $1.

Usually when I start checking bearing clearances on a stock rebuild, if the crank is in good shape the bearings are too tight for my liking, not too loose. Was the motor subject to abuse or bearing failure before you rebuilt it? What condition was the timing cover where the oil pump gears rub against it?
 
personally, I would pull the motor and properly set up the bearing clearances. Plastigauge can typically be found at NAPA, or at this point, you can get it many places online. Dave is the expert on these motors and has the knowledge of what clearances are ideal and has the eye to spot problems.

I think you can get away with running a heavier weight oil, but I think it's just masking the problem and its only going to get worse with additional bearing wear.

I personally run 20w-50, only because I was looking to generate the above mentioned oil pressures( I get 30ish psi hot idle, 50ish psi hot cruise). My motor is bone stock on the bottom end with 110k so my clearances are less than ideal plus I have the original pressure relief valve that could at this point be weak, and even with the heavier oil I don't see pressures exceeding 55psi even when cold.

I tossed in the heaiver oil just to see if the pressure would go up. It did, but only rose about 5 psi globally. Next oil change I'll switch back to a standard weight oil. I live in the North East, but I only drive the car from late May until September so the ambient temps are at least in the 70's. I def would not use a heavier oil if you plan on driving the car in colder temps. Over the winter I had to pull the oil filter and the small amount of oil that came out was very think due to the temps.

Anyhow, in my case, my pressure isn't ideal, but the engine is tired. In your case, since the bearings are new, I wouldn't feel that your pressures are acceptable.

Jay, I don't like 20w50 because it starves the motor on startup and until you get some heat into it. David Neibert used it on his motor and while the bearings all looked fine, his piston pins showed definite signs of insufficient lubrication. Aftermarket pistons have forced pin oilers but OE pistons do not, so the piston pins are one area that would concern me when using such a heavy oil. I have used 15w50 for years with great results and while it doesn't seem like a big difference in weights, the 15w50 definitely pours a lot easier when cold. I see no issues with running the 15w50 in northern climates in the summer.
 
Jay, I don't like 20w50 because it starves the motor on startup and until you get some heat into it. David Neibert used it on his motor and while the bearings all looked fine, his piston pins showed definite signs of insufficient lubrication. Aftermarket pistons have forced pin oilers but OE pistons do not, so the piston pins are one area that would concern me when using such a heavy oil. I have used 15w50 for years with great results and while it doesn't seem like a big difference in weights, the 15w50 definitely pours a lot easier when cold. I see no issues with running the 15w50 in northern climates in the summer.

You know...I might even have 15w50 in there now. Honestly, I have put about 12 miles on the car in the last year and a half so I don't remember what I tossed in there. Whatever Mobile One sells in a 5 quart container in heavier weight oil was what I used. Perhaps it was even 40 weight....

Anyhow, I guess the point I was trying to make was that my engine is original on the bottom end, even the pressure valve is original, so lower pressures that I see can be explained and expected. I'll just run this engine until it pops, or until I have someone ::cough, you, cough:: build me a discusting motor someday. In his case, with new parts installed, I wouldn't feel comfortable without knowing the clearances if that were me.
 
I run synthetic 15w50 in my built block and see hot idle of 50 and hot cruise of 78-81 with bearing clearances of .003". Definitely enough to build a wedge. My cold cruise of 99 concerns me a tad though. :eek:
 
I run synthetic 15w50 in my built block and see hot idle of 50 and hot cruise of 78-81 with bearing clearances of .003". Definitely enough to build a wedge. My cold cruise of 99 concerns me a tad though. :eek:


I'm running Mobil 1 15w50. I'm showing 82 - 90 lbs on startup and about 40lbs at idle after warm up. Just driving around I've got about 60 lbs. (Autometer electrical gauge.)

eddie
'90 5-speed SC
'97 LX sport
 
Usually when I start checking bearing clearances on a stock rebuild, if the crank is in good shape the bearings are too tight for my liking, not too loose. Was the motor subject to abuse or bearing failure before you rebuilt it?

This motor had been rebuilt once before with (I was told) approx 60,000miles on since the build. No damage was done to any internals, but the old bearings were a good bit worn (copper showing on about half of them - rod & main-, with grooves or gouges on bearing surface.)


What condition was the timing cover where the oil pump gears rub against it?

In my un-expert opinion it wasn't bad. Light circular scratching from the gears...you could barely catch your fingernail on.

So...pull timing cover, replace relief valve. Otherwise or if that doesn't work, engine has to come back out to check bearing clearances? Is there anything anyone can think of that might cause this that would be easy to check? One good thing to do would be double check the pressure reading. Anyone had problems with and Autometer oil press. sending unit before?

You know...is the relief valve actually a relief valve, or is it a primitive oil pressure regulator? Is it meant to be cracked open most all the time, or to open suddenly to prevent damage due to excessive over-pressure?? I mean, in essence it is both, but when is it supposed to be relieving pressure?

Well, by the way things are going today...I should just go to bed. Had to come home early to take care of a flooding basement / garage. Sweet huh? Not to mention the drive to get home...had to take the red sc through some flood waters in town... :eek:
 
i'm using 5w-30 synthetic on my 100% stock 1990 sc (145k km ~ 80k miles)

thats what it's had from the start...

is there any reason I should be using something else?
 
toronto_1990sc - If you're all-stock or at least mostly stock, I'd just use the 5W-30 - since you're living up north. I use 10W-30 in the summer on my mostly-stock SC's sometimes. There are a coouple of active oil choice threads going on right now, if you haven't seen them yet. Even a poll! :p The reason I ask about oil now...well, with this rebuilt car, I'm trying some different things so there are many more factors to consider. :rolleyes:
 
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