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Old 04-20-2017, 10:30 PM
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Oil Pressure Plug Size & Type? Gen 1 350

Hello, my Gen 1 350 010 block has an aftermarket oil pressure gauge running a line to the hole at the back of the engine by the distributer where it has a brass fitting; I need to remove all the fittings and would like to plug the hole properly.

What size plug do I need? And what type of plug, steel/brass/inset/square pattern/with threadlocker on threads etc. - there is a million types out there not sure which one is the proper one for an oil pressure port. Thanks for any info.

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Old 04-21-2017, 12:17 AM
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The thread in the oil pressure sending unit hole by the distributor is 1/8" NPT. I would use a hex head brass plug with 1/8" NPT threads. No thread sealer is needed.
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Old 04-21-2017, 12:44 AM
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Quote:
Originally Posted by MouseFink View Post
The thread in the oil pressure sending unit hole by the distributor is 1/8" NPT. I would use a hex head brass plug with 1/8" NPT threads. No thread sealer is needed.
Okay, thats a big help mouse - thanks.

Btw, do you happen to know roughly what the torque spec should be?
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Old 04-21-2017, 06:28 AM
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torque'n

just a good tight with socket wrench is fine. i would use anti seize
on the threads and just a good tight'n
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Old 04-21-2017, 08:47 AM
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NPT fittings do not have torque values. Pipe threads are tapered and seal themselves.

You don't need any thread dressing on brass NPT fittings.
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Old 04-21-2017, 11:48 AM
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Quote:
Originally Posted by MouseFink View Post
NPT fittings do not have torque values. Pipe threads are tapered and seal themselves.

You don't need any thread dressing on brass NPT fittings.
Okay great; found some brass 1/8 hex's as you reccomended and ordered them so should have this installed shortly. This will permanently fix any possibility of another oil spill in the cab... had half a quart or so leak out on carpet and ruin it all due to cracked tube; will go with electric pressure sending unit in future at some point, no more oil lines in cab!
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Old 04-21-2017, 12:11 PM
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The electric oil pressure sender unit has 1/8" - 27 NPT male and the engine block has 1/4"-18 NPT,female. You will need to use a brass 1/4-18 NPT male to 1/8"-27 NPT female brass adapter fitting.

You need to use a brass 1/4"-18 NPT plug until you install the brass adapter fitting and oil pressure sender.
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Old 04-21-2017, 02:42 PM
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Quote:
Originally Posted by MouseFink View Post
The electric oil pressure sender unit has 1/8" - 27 NPT male and the engine block has 1/4"-18 NPT,female. You will need to use a brass 1/4-18 NPT male to 1/8"-27 NPT female brass adapter fitting.

You need to use a brass 1/4"-18 NPT plug until you install the brass adapter fitting and oil pressure sender.
Okay very good to know; would really like an autometer electric eventually - but the sending units alone are pricey and right now I have a whole truck to build so need to conserve funds and plug the whole for now, but when its time will go that route for sure.

Ran into one more issue just now pulling the gauge set; the temperature gauge has its own hole in the block between the first and second header on the drivers side, it looks like it would take a pretty large plug - could you guys help me out again with what size this is and considering its coolant should go brass or steel? Thanks!
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Old 04-21-2017, 09:35 PM
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Was able to solve the coolant issue so my last post can be ignored; found a large brass plug that came with the truck which fit the coolant hole.
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Old 04-22-2017, 10:07 PM
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This turned out to be a can of worms. Looks like previous owners installed their aftermarket gauge sending units in place of the stock sending units on block (my dash oil and temp gauges never worked) - pretty sure the temperature hole between header 1 and 2 that I just plugged on drivers side head is where the temp sending unit goes for dash gauges and in the back of the block by distributer has got to be where my oil pressure gauge should go as I dont see one anywhere else, does that sound right?

I just searched for oil pressure sending unit and there are two completely different types showing for my year make model truck, there is the large bell style like this:



And then there are these small ones like this:



Is the small one above just for an idiot light? As I do not have an idiot light lens in dash; however, I just read on a forum that perhaps the choke may be using this idiot light sensor - what do you guys think? Just not sure if I need both considering there is no dash oil light at all truck is 81.

Any help is appreciated.

Last edited by fourbarrel; 04-22-2017 at 10:33 PM.
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Old 04-23-2017, 12:33 AM
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Yes you have it correct.. Starting in 1968, the single contact temperature gauge sender goes in the threaded hole in the head between 2 and 4 exhaust ports. Prior to that, the red-green/ hot-cold light, two contact sender was on a threaded hole in the intake manifold near the thermostat housing. The oil pressure gauge or idiot light sender and dark blue wire goes in the threaded hole near the distributor.

I don't see how a electric choke conversion power wire could be connected to a oil pressure port. I connected the electric choke conversion power wire on my 1962 Bel Air to the yellow windshield wiper power wire. My 1962 Bel Air is equipped with a 1967 Q-jet. The WS power wire is turned on when the ignition key is the run position and is off with the key in the accessory position.
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Old 04-23-2017, 03:51 AM
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Quote:
Originally Posted by MouseFink View Post
The oil pressure gauge or idiot light sender and dark blue wire goes in the threaded hole near the distributor.
Thanks Mouse, but your saying the actual oil pressure sensor would go by the distributor too correct? Not just the idiot light sensor

Quote:
Originally Posted by MouseFink View Post
I don't see how a electric choke conversion power wire could be connected to a oil pressure port. I connected the electric choke conversion power wire on my 1962 Bel Air to the yellow windshield wiper power wire. My 1962 Bel Air is equipped with a 1967 Q-jet. The WS power wire is turned on when the ignition key is the run position and is off with the key in the accessory position.
What I read on some forum not related to my specific engine was a guy mentioned that there should be a two prong oil pressure sensor that would tell the choke to turn off I think when oil pressure is there, something along those lines. I have my dash torn apart and there is 100% no oil lights of any kind, so I don't see why I would need an idiot light sensor - but at the same time don't understand why parts places are showing it for my truck.
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Old 04-23-2017, 09:17 AM
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do you have electric choke? if so two prong oil pressure switch should be used because,,, cold start.oil pressure comes up, activates choke warm up, cold engine stalls, no oil pressure, so choke stops opening. you can run this pressure switch and oil pressure sending unit from 1\8 port by distributor using T if you wish
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Old 04-23-2017, 01:36 PM
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Quote:
Originally Posted by gc408 View Post
do you have electric choke? if so two prong oil pressure switch should be used because,,, cold start.oil pressure comes up, activates choke warm up, cold engine stalls, no oil pressure, so choke stops opening. you can run this pressure switch and oil pressure sending unit from 1\8 port by distributor using T if you wish
I believe I read somewhere that the two prong is only for newer cars, I think - could be wrong; it doesnt show 2 prong units when I do parts searches.
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Old 04-23-2017, 03:22 PM
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The two prong coolant temperature senders in the intake V8 manifold with a light green and a dark green wires were for the red-hot / green-cold lights in the instrument cluster. In 1968, the water temperature sender on the Chevrolet small block V8 was moved from the intake manifold near the thermostat to the left head between #2 and #4 exhaust ports.
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