Oil pressure and highway speeds

Rolltide1006 · Jan 12, 2019

Hello all and I apologize if this issue I am having has been answered before. I can’t find my particular issue discussed on google

Oil is full and is Motorcraft 5w-20 with a Motorcraft oil filter. Wiring to the autometer gauge is [emoji108][emoji2532]

I have a 97 GT and hooked up a autometer oil pressure gauge to know where I am at. The motor is a 4.6 2v and has PI heads, blower cams and was rebuilt 2k miles ago. Oil pressure is 70-80psi on cold start and I never lose it or see it drastically change. When nice and hot, I am idling with 20-25 psi. Once i bump the throttle it shoots to 50 psi. When I accelerate hard from a stop I see a nice gradual climb with pressure all the way to 60-70 psi. When I am driving on the highway is when I notice a slight fluctuation. When I am going 70-75mph in 5th gear at about 2200 rpm I noticed the meter was at 50 psi. I give it throttle and the needle will drop slightly down to about 45 psi and once I let off the throttle it will jump back to 50 psi. When I am at the same speeds and drop it into 3rd and accelerate the pressure goes to 55 and doesn’t climb as quick as it does when I am messing around in town. This is my first time having a aftermarket oil pressure gauge so I may be just a little paranoid. Just wanted to hear yalls opinions and/or experiences. Am I crazy or what? Thanks in advance!

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Rolltide1006 · Jan 12, 2019

Is this normal?

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castine917 · Jan 12, 2019

All of those numbers are within normal.

Silver95bird · Jan 12, 2019

Keep in.mind the Ford oil pressure light doesn't come on until about 6psi.

If you think the running pressure is low, try 5-30 like the 4.6 was originally speced for.

castine917 · Jan 12, 2019

Silver95bird said:
Keep in.mind the Ford oil pressure light doesn't come on until about 6psi.

If you think the running pressure is low, try 5-30 like the 4.6 was originally speced for.

Light wasn't mentioned. Aftermarket gauge with all readings in normal.

OLD H2S · Jan 12, 2019

The new Ford Mustang oil is 50 weight...think Ford finallly said screw gas mileage, no more warranties.
BTW after killing a new motor in 10 miles with 5-20. I started to look at thicker oils and the new Ford popped up and the BMW 60 weight is out there, so the old BS about tight engine tolerances is just that.
I really really liked that engine I killed and your numbers are the same as mine running a high flow MMR Hurricane pump with billet gears.

Rolltide1006 · Jan 12, 2019

OLD H2S said:
The new Ford Mustang oil is 50 weight...think Ford finallly said screw gas mileage, no more warranties.
BTW after killing a new motor in 10 miles with 5-20. I started to look at thicker oils and the new Ford popped up and the BMW 60 weight is out there, so the old BS about tight engine tolerances is just that.
I really really liked that engine I killed and your numbers are the same as mine running a high flow MMR Hurricane pump with billet gears.

How did you kill the motor in 10 miles using 5w-20?

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Silver95bird · Jan 12, 2019

castine917 said:
Light wasn't mentioned. Aftermarket gauge with all readings in normal.

I can see that. Thanks Capn.

OLD H2S · Jan 13, 2019

Got jumped by a Porsche and had to beat him up...do stupid stuff win stupid prizes. See it never goes away, even when your in your 60's.

96blak54 · Jan 13, 2019

I run 5w-20 in my junk built 5.4l. 6200rpm revs no problems yet.

01yellercobra · Jan 13, 2019

OLD H2S said:
Got jumped by a Porsche and had to beat him up...do stupid stuff win stupid prizes. See it never goes away, even when your in your 60's.

Is that the engine that died in 10 miles? I'd say you had another issue creepin up on you. Jumping on it just accelerated the outcome. I ran 5w-20 for a break in oil in my big bore stroker. It saw full boost within 20 minutes of first start up. Never had an oiling problem with that engine.

96blak54 · Jan 14, 2019

Method of break in.....car idles good, no leaks, its to temp....FULL THROTTLE!

OLD H2S · Jan 14, 2019

Well if you follow my build threads, I just finished engine build number 13. Some of them were just tear downs to see how a particular part or idea was working. That engine that had a rod knock in 10 miles was not a perfect build but the normal type of throwing in all new bearings, rings, seals and that was build number 4 on that block so I was surprised to have a rod knock so fast. I would have to dig through my notes to tell you if it was a King bearing or Clevite and which series because I was trying all different types and that is one off the reasons for the tear downs is to see what is advertising BS and what will hold up. The Ford type solid aluminum bearing is a very good design and was new at the time and has stood the test of time now but it is very hard and if any close spots are around there WILL be damage. The King bearings come in softer compounds and get harder for higher HP and for rebuilding engines the moly coated types are the best because they wear in easy without seizing and scoring.. the coatings take the hit and it is easy to see problems on tear down and inspection.
That is a lot of information right there for anyone that is building an engine if you look. I am not an engine builder but I have built many engines of all different types and have had engines last 30 minutes that were made by the big names in the business for Terminator engines. This is the reason I have started to do my own builds and you can not stand on dyno numbers, you must do tear downs to look and measure. Every time I help people with engine problems I see mistakes, that is why unmollested virgin cars now get the most money and all the car shows use crate motors on build ups, they might not be the super high end stuff we see in HotRod magazine every month but they work with no head aches. If I had to do it all over again....

OLD H2S · Jan 14, 2019

More info, the rod bearing that was bad was number 8 nearest the rear main bearing. This is where all the junk collects when not cleaned out when building an engine even for Ford on the first build. I have saved my original rear main in my bearing library to show people the amount of junk in a factory build. The bad bearing did not harm the crank? Now I have started to use a plus .001 rear main bearing for extra dirt clearance?
When pro's build engines for high RPM/longevity contests they run big clearances and high flow pumps and do not care if the pressure is low from big gaps.
So are big gaps or big pressure better?

01yellercobra · Jan 14, 2019

Most of us probably have engine builder stories. I've built a few over the years as well. My first mod motor I farmed out to be safe. I should've just built it myself as thats what ended up happening in the end. My first clue should've been when he "forgot" to order the head gaskets, but they were on the bill.

Rolltide1006 · Jan 14, 2019

01yellercobra said:
Most of us probably have engine builder stories. I've built a few over the years as well. My first mod motor I farmed out to be safe. I should've just built it myself as thats what ended up happening in the end. My first clue should've been when he "forgot" to order the head gaskets, but they were on the bill.

Lolol. Forgot to order head gaskets. Ya my first machine shop installed my forged rods in backwards [emoji2]

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01yellercobra · Jan 14, 2019

Rolltide1006 said:
Lolol. Forgot to order head gaskets. Ya my first machine shop installed my forged rods in backwards [emoji2]

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I found some other things after the fact. Like there was supposed to be stainless steel rings. But he installed moly. It was an expensive lesson.

Rolltide1006 · Jan 14, 2019

01yellercobra said:
I found some other things after the fact. Like there was supposed to be stainless steel rings. But he installed moly. It was an expensive lesson.

Thats no good. I know of this lesson as well lol.

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Rolltide1006 · Jan 16, 2019

Meh, this morning’s commute was crap. I was in traffic for 35 min bumper to bumper. I noticed that my oil pressure was telling me 12.5 at idle at times. When I finally got up to speed while in 5th gear i was at 40psi. I know that these readings are still in spec, but I hate how they keep getting lower

I am going to change the oil after work today.

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evilcw311 · Jan 16, 2019

Rolltide1006 said:
Meh, this morning’s commute was crap. I was in traffic for 35 min bumper to bumper. I noticed that my oil pressure was telling me 12.5 at idle at times. When I finally got up to speed while in 5th gear i was at 40psi. I know that these readings are still in spec, but I hate how they keep getting lower I am going to change the oil after work today.

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