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Junior Charter Member
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Discussion Starter #1
Hi Everyone,

Been a long, long time since I posted anything and am getting back into the car after a few years away from it. My wife and I have enjoyed the car but work always seems to get in the way (starting a new business can kick your &$#@$) and we are changing that. We have an MK3.1 that was completed back in 2006. Nothing fancy motor wise, just a little 302 bored .030 from an 89' Mustang. Whenever we take it out it out I always monitor and worry about the oil pressure. At start up it is in the 40-50 range, which I think is pretty standard and ok. But once at running temp, it drops to about ~15-20, closer to 15 (will take a video today and post). When you rev the motor it will increase (good) but I am always concerned that it is not enough. When the motor was built, the builder put the wrong pickup in and it was sucking air, we replaced the pickup and that corrected the pressure at that time, but it has never been the same and seems to be progressively worse. From all my research it seems like it could be a couple of things, oil pump or main bearings. In either case, it is best to pull the motor to check it out, right? If I have to pull the motor, this one is not going back in as it has been too problematic to keep pulling (already pulled once). I am thinking that I am just going to drive this with the current pressure and if/when she blows, I'll replace the motor with a new crate motor. Curious to hear everyone's thoughts and advice.

Thanks!

Tim
 

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15 PSI at idle is fine for Ford small blocks, if that's at higher RPM's then it's a problem. That said, I too feel better with 25 or more, but it's not really a problem.
 

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A SBF, once at operating temp, will drop the oil pressure down into the 15 range at idle. Pretty normal. As long as it picks up with RPM. If you're seeing 30-40 or more while at speed it's probably OK. You'll have guys cite higher numbers, and never drops below XX, etc. But what you're seeing is pretty normal for a mostly stock motor that's been driven a while. Your comment that it's getting progressively worse is a little concerning though, so I'd definitely keep an eye on it. What weight oil are you using? You might be able to improve things a little there. Likely in the end you are talking about bearings vs. the oil pump itself. But I'm betting you have a lot of miles left.
 

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Junior Charter Member
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Discussion Starter #4
Thanks for the responses, makes me feel a little better and that I may be over thinking it (tend to do that sometimes) :).

Right now I am running 10-30 and it is due for an oil change. Any input on what weight and filter I should use?
 

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Thanks for the responses, makes me feel a little better and that I may be over thinking it (tend to do that sometimes) :).

Right now I am running 10-30 and it is due for an oil change. Any input on what weight and filter I should use?
I'd run a good quality 10w/40 like Brad Penn and filter Mobile 1. I picked up 5 psi just switching filters to one with the larger oil inlet holes. Scott
 

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MY advice, go over to the diesel section and buy any brand 15w-40 diesel oil. It will exceed any specs for gas engines, is cheaper than the 'boutique' race oils, which is a waste of money on a high milage street engine. That and a good filter may help.
 

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For some reason I had in my head that the FORD spec for a 302 was 25 psi at hot idle. I want to say that Big Blocker provided that number in a thread not too long ago, but I may have that wrong. He's usually a fount of knowledge on all things FORD OEM, so hopefully he'll chime in.


John
 

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Discussion Starter #8
Just was out looking at some other stuff and a thought hit me. Could it be that I have the wrong sending unit? I am running the Autometer Pro Comp gauges that came with the kit but I am not sure the sending unit is right. If I were running the stock sending unit would that register lower or higher psi?

Sent from my SM-T810 using Tapatalk
 

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If you are worried that the problem (if there is one) is getting worse, send in an oil sample to Blackstone Labs and have an analysis performed. If there are excessive wear metals present it will show up, particularly if you have a couple of successive tests done.
 

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15-20psi at idle is fine for oil at temp. I would run 10w-40 in an older 302.

If you change the oil and it has a very golden color, then the bearings are wearing.

The pressure is based on the clearances. They get larger as the engine wears and the oil pressure will be lower. If you have 40psi at redline, that should be plenty for street use.
 

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FFCobra Craftsman
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Do some research on the sending unit and order a new one that is specified to match your gauge. They are usually in the <$30 range so it's an inexpensive test.
 

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Too Cheap to paint!
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Same as above, but can add:

Buy a cheap mechanical gauge, and compare pressures

just drop the pan and put in a high-volume oil pump. Maybe the pump is loose?


Just for comparison, my last two fresh motors run 55-60 PSI cold at revs, drops a little when warm, but idle pressure stays up in the 40's.
 

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Why would you recommend putting in a high volume pump when his pressure is normal per Ford's info? That and high volume pumps are known cause potential problems.
 

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Too Cheap to paint!
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Why would you recommend putting in a high volume pump when his pressure is normal per Ford's info? That and high volume pumps are known cause potential problems.
If the motor is "loose", just have more oil pushed through to keep things lubed. I have always run a high volume (not high pressure) pump, no issues from oil volume, on all four motors.
 

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Discussion Starter #15
This is all great info, and I appreciate all the input. I ordered a mechanical gauge which should arrive tomorrow. Plan on testing with that to rule out the sender, and will up the weight on the oil change. Will let you all know what I find.

Tim
 

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Why would you recommend putting in a high volume pump when his pressure is normal per Ford's info? That and high volume pumps are known cause potential problems.
If the motor is "loose", just have more oil pushed through to keep things lubed. I have always run a high volume (not high pressure) pump, no issues from oil volume, on all four motors.
High volume vs high pressure pumps....
I’ve always wondered how you pump more oil through the same size pipes without raising the pressure?
 

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The high vol pump gives the high idle pressure. There is a risk of distributor gear failure/wear. It is a lot of load.

With a standard pump you will see 15-20psi. I've had 6 race motors all with standard Melling pumps and .0025ish clearances, all have 15-20psi idle and 45-50 at redline. I use 10w-40 race oil.
When it dips down to 10psi or less coming in to the pit, I know its time to refresh. I only had two of the engines make it that far. Usually I drop a valve, break a spring, or break a valve before it wears out.
 

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Snake Farmer
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You would probably see an increase in pressure, even with just fresh oil, and a new filter, but the 10-40 should definitely bring it up.

Some claim certain oil filters can help with oil pressure. Might be worth some research..
 

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Official OLD GUY
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FORD Factory Spec

Ford's spec for oil pressure is stated in their service repair manuals as: "At normal operating temperature, set engine speed to 2000. Oil pressure should be approximately 15-20 Lbs. minimum."

FWIW, I [personally] have always used 20 Lbs. as my minimum pressure with any engine I've built - no matter what pump (Standard or Hi-Volume) I have installed.

There are those who will jump on this, saying that no SBF ever needs a Hi-Volume pump . . . Depends on how the engine is put together and its ultimate purpose.

Doc :beerchug:
 
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After reading all these post............
.............Whats my problem?
Cold Eng start up, I read 80 on oil pressure @ idle ( same reading for the last 4 years) .
Five minutes later(at 50 mph) I read 40-50 on oil pressure.
....An hour later (in 80-90 degree outside air temp) After Eng is FULLY warmed up.
I still read no less than 40 psi at idle.And 50 psi at cruise speed .
Engine Modified ...1990 Mustang GT 5.0 302/345
 
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