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6 Cylinder Block - Oil Feed Union

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Dace

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Can any one tell me the thread form and size of the union into the block which is then used to connect the flexible pipe to the oil gauge.

When winding the existing union into the block under normal loading the thread appears to have its crest cropped when removed.

I would like to clean the block thread up and confirm the size and form before trying a new union.
 
Hi Dace, I do not have a clue as to the thread size you need. However, you might take the union to a well stocked hardware store or auto supply. They usually have thread gauges there and you might get lucky and identify what it is.--Fwiw---Keoke
 
Not wanting to damage the thread in the block I opted for a "proper" union from AH Spares. On receipt of the new item I was suprised by the very small drilling thro' the union. Thoughts of it being that size to attenuate the ripple from the oil pump to the gauge crossed my mind. The second point that was obvious was that the theread was tapered. Following the careful tightening of the union into the block I cranked the engine on the battery with the plugs out and watched the oil pressure gauge. (With the previous "full bore" union the pressure quickly went to approx 50lb.in. With the new union the pressure did not register on the gauge, although oil was apparent flowing at the rocker arm top drillings.

Anyone else had problems with these "correct" unions. The garage is cold and as a consequence the oil at its thickest but to get no response fron the gauge is a worry. I have even taken the feed pipe of the gauge and run the pipe ito a clear plastic bag but no flow is apparent.
 
My original fitting has a quite small oriface as well, but pressure is pressure, you don't need much volume to run the gauge.

You might try loosening the fitting at the gauge to bleed the air off, it's probably compressing enough to minimize your gauge reading
 
Yes- the correct fitting has a very small hole through it for the purpose you stated. Gage vibration is also attenuated by having a little residual air in the line to act as a shock absorber. It won't affect the gage accuracy, pressure is pressure, whether it is hydraulic or air.

You did say that you removed the line at the gage, & no flow. It would appear that the tiny hole in the block fitting is somehow plugged. Verify by removing the flex line where it connects to the block fitting. If oil does come out there, the line from block to gage may be plugged.
D
 
You can check to see if your oil gage is working properly by hooking it up to a compressed air line, slowly add pressure and see if the air gage and oil gage are reading the same. I was scratching my head with a 'no oil pressure' problem recently and it turned out the gage was broken.

And yes, to add to the confirmation, the fitting on my motor and my spare motor have the very small hole in it.
 
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