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Oil high pressure


chefabg123321
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Just bought a 72 vert Q code. Just sorting out a few issues. Getting extreme oil pressure reading from a stock gauge when engine starts up and is "cold". Gauge is all way to right ,up to the second to last "line" , I don't understand the stock gauge, not sure if this is acceptable or not? I have four markings on this gauge and no numbers, two little lines on either side and two more just inside these.

Well, after normal highway driving car at 55 mph for about 15 mi, gauge settles down to middle reading. After highway on slower roads gauge picks up again to high. Any ideas? [/align]

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Others will chime in, but the 71-73 gauges are notoriously inaccurate. They serve more to indicate operational status than accurate readings. That being said, it sounds like you have normal (i.e. decent) oil pressure. Purchase or borrow a mechanical pressure gauge to install at the oil pressure switch port to check for the real pressure readings for peace of mind.

 

Also, it sounds like the gauge is reading just a tad high. There are ways (Midlife & others can elaborate) to adjust the reading.

 

I'm thinking (based on recollection the last time I checked mine with a mechanical gauge) cold startup oil pressure is about 65-70psi, normal driving is around 45psi, warm idle can drop to 20-25psi.

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+1

The wt of the oil you are using will also affect the reading. 1/2 to 3/4 is fine.

-john

(jbojo)

351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,

C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

 

Some Mod pictures can be seen at: [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=2026]Bojo's Garage[/button]

 

 

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This is probably not your problem but might be. The oil pump on most Ford engines can get a jammed bypass in the oil pump and cause high oil pressure but not common. I had a friend call and ask what brand oil filter I used and I asked why. He said he had put three different brands on his Ford pickup and they all exploded. I talked to a friend at the ford dealer and he said it was probably a piece of valve stem seal broken loose and sucked up by the oil pump and holding the bypass valve closed. Another symptom of this is no oil pressure. The trash gets in the oil pump and locks the rotors up and breaks the allen key drive from the distributor to the pump so no pressure. You ask how can the trash or rubber seal get into the oil pump when the pickup has a filter screen on it? The screen gets clogged over time with trash, sludge and parts of the seals as they break off. Ford designed the screen with a round hold that is blocked when everything is normal. When the suction on the pump goes up, due to the trash in the screen, it sucks the screen up and opens the hole that will let big chunks it. This is to prevent burning the engine up. When I took his oil pan off sure enough it had lots of pieces of the stem seals in the pan and the screen was blocked. We put a new oil pump & screen in but could have just cleaned the old one but didn't. We pulled valve covers and changed the seals without pulling the heads, what a pain. Air pressure to hold valves closed and lever you put on rocker stud to compress spring and take the keepers off and change the seals. We washed out the heads and blew air down the oil returns and put the pan back on and everything was good for years.

Probably not your problem since no exploding oil filters or lack of oil pressure.

David

When a man is in the woods and talks and no women are there is he still wrong??:P

David

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Throw a mechanical gauge on it before doing anything else. As has been mentioned the stock gauge isn't much more useful than a warning light.

 

I would hook up a gauge to the port by the fuel pump and leave it under hood, noting the cold pressure. get the engine good warm and check it again. If both reading are ok, then...

 

It could be that someone has put a high-volume or high-pressure pump in the engine in the past and the stock gauge isn't designed for that, it's graduated for stock components.

Matt

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I am going to guess bad sender or bad ground. What's the water temp gauge doing?

 

Agree with the mechanical oil pressure gauge suggestion. I have one on a 't' where the sender is. It's nice to see it when I am working under the hood.

'Mike'

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

 

Pics of modifications included in: [button=http://www.7173mustangs.com/thread-1973-convertible--3335]My Garage[/button]

 

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The after market sending unit are notorious for being way off on resistance values. I bought 3 and none were within tolerance. Took them all back and cleaned up a good original one. It is in tolerance and works as properly as the poor OEM gauges permit. The same is true for the temp sender as well.

 

Chuck

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+1

I wound up using my original one too. The newer ones were giving me up to 1/4 difference with the engine warmed. Now it's at 1/2 at idle and 3/4 at 2000rpm when warmed. The newer senders were giving me readings on the lower side.

-john

(jbojo)

351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,

C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

 

Some Mod pictures can be seen at: [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=2026]Bojo's Garage[/button]

 

 

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+1, on using a real guage to verify what pressure you are really getting. You will never have that comfort feeling if you don't. I install a tee in the line when I'm in testing phase. Once I'm familiar with what's "normal", I'll take out the under hood guage and plug the side of the tee.

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I am going to guess bad sender or bad ground. What's the water temp gauge doing?

 

Agree with the mechanical oil pressure gauge suggestion. I have one on a 't' where the sender is. It's nice to see it when I am working under the hood.

 

Water temp gauge is great, very low to middle at most

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My mechanical water temp gauge gets to just a hair over the first mark and on the digital readout it's 184* from a second temp sensor that I have installed. Using a 180* thermostat.

-john

(jbojo)

351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,

C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

 

Some Mod pictures can be seen at: [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=2026]Bojo's Garage[/button]

 

 

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