Oil Pressure Guage Mystery

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PrairieDrifter

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How and what do mechanical gauges do differently? What is the time frame to work out for install of a mechanical gauge?
A mechanical gauge is getting direct supplied oil, from one of the main oil galleries that feed oil through the block. So it's reading it has the literal oil from the engine flowing into the gauge, moving the needle through a mechanism in the gauge.

So basically it's just an arm that moves due to hydraulic pressure, and almost never fail, and are very accurate. Like any other hydraulic pressure gauge.

It'll take you a couple hours to install. Depending on where you install it. I tapped into the block in a 3/8ths plug above the oil filter on the drivers side of the block. Your engine probably has a sensor there, that it'll need. So you could get a 3/8 y fitting to accept the old and new fitting.

Do not get the plastic lines! Get the copper line.
 

JamesSam

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This is generally where it hangs out. I'm hoping a new pressure sending unit will do it for now. Probably trying to switch it out Saturday
 

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Randy and Easton

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We have older style gauge and it usually hangs out at about 1 o’clock and higher when at highway speeds…
 

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JamesSam

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Yes that is where this one used to live riding down the highway. I miss it.
 

JamesSam

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Does anyone have recommendations for the best aftermarket part?
AC Delco? Is there anything better?
 

JamesSam

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Redfish, thanks for the feedback! Much appreciated! Where did you get the Standard version? Online, NAPA, Advanced Auto...?
 

Camar068

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with it hooked up to the meter like in the pic.....you can hook up a syringe with tubing and push to vary the pressure to test. Also, you could hook it up to your air compressor with it set to a low pressure to test.....vary the pressure to test accuracy.
 

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When my block was out I used a 1/8" NPT adapter with two 1/8" NPT ports so I could attach the Oil Pressure Switch, for fuel pump relay protection and a plastic hose fitting for the manual pressure gauge on my dash. The manual gauge uses a small tubing to the gauge to constantly monitor pressure, where the electrical unit uses a sometimes sketchy pressure diaphragm unit with a rubber bladder to estimate the pressure and send a signal from .05 to 5v. The problem is the electrical versions are easily subjected to ground corrosion and faulty rubber bladders on the cheapo sending units...

Getting to the rear engine block, where the modification needs to happen is nearly impossible with the engine installed, due to the proximity to the firewall and the space required to install the main adapter and then plumb and leak proof the fittings... I had to wrap teflon to build up so the angle of the fittings did not face towards the block or away from where they would actually fit without obstruction. It was several attempts to get it correct, when out of the engine bay, by wrapping enough teflon tape until it sets the angle of the ports just right... I would not want to attempt it with engine installed. There is no way to turn the wrench. It is an impossible angle to get to.
You'll need to dislocate your thumb to do it and then relocate it back after the install...

My engine came without the oil switch installed and the pressure gauge in its place. I would not recommend eliminating the pressure sending switch, as it allows the truck to run on the 1987 without a functioning fuel pump relay. Or you'll get stuck on the highway without fuel pressure... WHEN the Fuel Pump Relay fail's...

The OEM fuel pump relays did come with fly back protection from the factory, so every time they load and unload, they do not kill the alternator circuit.
Buying a quality relay, from Dephi, GM or National is very important, as the aftermarket relays are ****.
Even buying OEM quality, they still fail and you should carry a spare...

Many builders replace these OEM relays with Bosch or aftermarket cube style relays, (without flyback protection)... and then you are really in for trouble.

The stainless fitting (Second picture belowe) is what I used... it allowed me to fit the switch to the side port and use the top port for the compression fitting to the plastic hose to my manual gauge on my dash, through the firewall. The brass unit works well too.

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This fitting VVVVV (Below) eliminates the very important function of the emergency oil pressure switch and should be avoided. It is the rubber diaphragm sending unit for the electric dash gauge... it works for old school engines, and would not be advised for the 1987 model year... These are not reliable... the engine heat kills the diaphragm way too fast... they suck and will lie to you about the most important thing... actual oil pressure...
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^^^ your casting numbers are here, under the blue wires...
There may be an oil port available near your oil filter, depending on the block you have. 1987 had several different blocks, from different factories.
Some had provisions for roller cam, oil ports, manual fuel pump machining, some came without any of these features.

Unfortunately, the casting numbers are located behind the block near the firewall and most likely are not able to be seen and confirmed when the block is still in the engine bay. The 1987 year engines are so close to the firewall, and at such an incline to the frame, there is no way to even use a mirror to inspect the casting marks for engine manufacture.

I tried for months... it is not possible on many 1987 trucks to see what your casting numbers are, unless you pull the head on the driver's side or remove the engine.
Borrow a bore scope from somebody, is my only advice to confirm casting marks. Removing the hood will not help. It will just piss you off, because now you have potentially broken your windshield, in order to find out you still cannot see the casting marks... (Hood accidentally goes through windshield, without a second set of hands during removal comments, please post here:)

If there's a 1/8" NPT plug near your oil filter port, you are in luck... Pic from the HAMB:
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Tap for the manual gauge compression fitting here. Just make certain the feed hose for the manual oil gauge cannot get any heat from the headers or exhaust manifold. It will be very close to your pipes, in this area. Copper tubing compression is better than plastic tubing compression fittings here.

Here's a copper compression tubing oil pressure fitting at the filter location, on a BBC:
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Little to no heat on your tubing, is the best solution, either way.
Be prepared to get a face full of oil when you pull that plug and have the parts ready with teflon tape... to close it before your engine pukes in your face, or perform this install during your oil change, to avoid the mess.

Close proximity to your exhaust may mean using 45 or 90 degree fittings here, and changing direction of your plumbing fittings, to avoid heat and to enable getting a wrench on anything... the exhaust in many cases will become the limiting factor. There is simply not enough room to work, on some engine access situations. Your linkage will be in your face, as well.
 
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JamesSam

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RanchWelder, lots of info here, thank you! You even began discussing the fuel pump relay and I don't know if you saw any of my other threads but the other main issue I am dealing with is my truck only running on the passenger tank. When switched to drivers side tank the power immediately dies(or rarely will die a minute or two after switching, it's Ben a while since I tried troubleshooting the fuel issues...) lots to discuss on that. We could message back and forth about it if your up for it. Anyway, I will definitely be re-reading your response several times to soak it all in. Thanks again!
 

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*been a while
 

Randy and Easton

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@RanchWelder great info! Beyond grateful for the info. Our OP gauge works great and I think it’s in a port on top side of block just below HEI I think. I always worried if I had to replace that how would we do it. The oil filter option gives us options if we end up there. Thank you sir

Randy and Easton
 

Redfish

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Redfish, thanks for the feedback! Much appreciated! Where did you get the Standard version? Online, NAPA, Advanced Auto...?
Ordered it from RockAuto. Used the discount posted on this forum
 

JamesSam

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Ordered it from RockAuto. Used the discount posted on this forum
So here is a snapshot of my current one from the top. I understand there are 60 and 80 psi versions. If I ask for a year specific one at an autoparts store they should pull up the correct one right?
 

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bucket

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This is generally where it hangs out. I'm hoping a new pressure sending unit will do it for now. Probably trying to switch it out Saturday

Unplug the sender and turn the ignition on. The guage should peg to max pressure. If not, there is a gauge or wiring issue. If it does, then proceed with trying another sender or verify pressure with a mechanical gauge.
 
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