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Oil pressure gauge  Rating:  Rating
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 Posted: 06-12-2005 04:53 pm
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Paul Koehler
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With the recent change of exhaust header, the harmony of the engine was displaced, resulting in moving hoses etc. to get at exhaust flage. After putting it all back and starting it up, I discovered that the oil pressure gauge tubing was not connected, and you can figure out the rest. A BIG MESS.

Trying to get the tubing reconnected has proved quite difficult, due to its positioning. I guess I'll have to take the carbs off to get at it, as I cannot affect enough pressure to get it to seat properly.

Does the hard plastic tubing seat all the way down on the spiget? Any proven ways to do this as the tubing is quite inflexible? Has anybody switched over to an electrical gauge? Smith's or otherwise? Does the sensor use the same port?

I have this vision of blowing the tubing in the middle of no-where or worse yet, deep frying my legs with hot oil with a gauge malfunction.

TIA,

PK-18849

 

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 Posted: 06-12-2005 07:14 pm
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Mark Rosenbaum
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The oil gauge 'pipe' does not have an unlimited lifespan, and when one shows a problem, it's generally best to replace it.  Delta Motorsports sells these at a very reasonable price.

It may be possible to successfully reattach a plastic oil gauge 'pipe' that has become detached from its fitting.  Here, I'd trim off 3 or 4 cm from the end of the 'pipe', apply sufficient heat from a heat gun to soften the new end, then push it onto the fitting's central spigot.  I haven't tried this as its chance of success depends strongly on the condition of the plastic 'pipe'.  A better repair would involve replacing the entire plastic tube with a high-pressure, high-temperature, oil-resistant hose of the proper size, and using a couple of hose clamps to secure the ends of the hose to the original fittings, but this would likely cost more than a new 'pipe' from Delta.

The 'pipe' fittings appear to use 1/8"-27 British Standard Pipe (BSP) straight-cut threads, not the similarly-named and -sized, but not quite compatible, US standard pipe thread.  Since BSP fittings are not common in the US, any repair would probably involve re-using the original fittings. 

One needs to ensure that the 'pipe' is correctly installed.  The interior part of the gauge-end coupling has a flat face with a recessed central region.  The oil gauge's threaded fitting mates with this recess and uses a traditional leather washer for a seal.  An oil-resistant o-ring should provide a decent seal if the leather washer is missing or damaged.

The interior part of the engine-end coupling has a tapered nose that fits directly into a matching depression in the brass male-male adapter ('union') that screws into the aluminum cover that in turn is bolted to the engine.  A close look at this adapter will reveal that (a) its engine side has a flat face, and (b) the engine-side threads are slightly tapered (making them 1/8"-27 BSP taper-cut threads).  It is vital to install the adapter with the correct side out, or leaks will surely occur.  (Engines with an oil pressure switch that activates the anti-run-on valve use a different adapter, but the general idea should be the same.) 

Whatever approach you take, be sure to protect the 'pipe' from cuts and abrasions in the engine bay and where it passes through the firewall.

Electrical  Oil Pressure Gauges.
I recommend using only a mechanical oil pressure gauge in a JH.  The 907 engine will often exhibit erratic oil pressure as an immediate precursor to catastrophic failure, and if one pays attention to the oil pressure gauge it's usually possible to shut things down before expensive damage occurs.  But electrical gauges -- particularly Smiths ones -- respond quite slowly, by design, and rarely provide a timely warning of these disasters.

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 Posted: 06-12-2005 09:55 pm
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Judson Manning
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As Mark points out, the easy thing is call Delta.

Option 2 is to go aftermarket and install a copper line that will last forever.  This will require taping and installing a correct 1/8 NPT fitting on the block.

 

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 Posted: 07-12-2005 02:42 am
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Paul Koehler
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Do you have any recommendations as to what brand works well in a JH, as far as after market mechanical oil pressure gauges go.

I re-installed the original line, but got to thinking about the copper line suggestion, and think I'll  go that route. I like the idea that it " bullet proof". Just one last thing to worry about in a 30 year old vehicle.

Thanks for the input.

PK-18849

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 Posted: 07-12-2005 12:45 pm
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Jensen Healey
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Just buy a new one. It should last another 30 years. My replacement is at least 5 years old and is soft and supple.

You could re-engineer every system in the car so it would last forever, but then you'de have a Rolls Royce!

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 Posted: 01-12-2006 02:34 am
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Paul Koehler
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I'm finally ready to put in a new copper oil pressure line, during the winter down-time. In order to get at the back of the Smith's gauge, does the whole instrument pod have to be pulled, or can the gauge itself be eased out?

Thanks

Paul Koehler-18849

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 Posted: 01-12-2006 03:30 am
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Mark Rosenbaum
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Assuming nothing is rusted in place, you can probably pull the gauge without removing the instrument pod.  The extra effort to pull the pod isn't all that great, however, and it's a good opportunity to make sure everything is tight, all the connections are clean and shiny, and replace the gauge lights.

For reference, I've attached a photo of the rear of the instrument pod, taken from an advertisement on eBay.

Attachment: dash - inst pod rear #2.jpg (Downloaded 56 times)

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 Posted: 01-12-2006 07:56 pm
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Paul Koehler
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Thanks Mark!

PK

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