1G What are These Holes on the Head?

[Pasta_Ricer]

Hello!
As you might know, I have a NT 4G63 '91 Galant. Today when trying to take out the alternator for service, I noticed these holes on the edge of the head plugged with bolts; one big 17mm bolt and two Allen wrench type screws.
I'm guessing they're coming from the oil passages? But I'm not really sure.
What I'm wondering about is that can I use these for an oil cooler? Or can they be used for an oil pressure sensor?
Thanks!

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[danl]

The 17mm and the small Allen next to it are to feed the turbo. People typically take oil pressure readings from the oil filter housing. The only reasonable way to run an air to air oil cooler is to run an ofh that has the proper provisions. For most builds, it isn’t needed.

 

[dwb]

The allen heads are bspt plugs and seal off the oil gallery. The bolt looking plug is the stock turbo oil feed location.

If you're looking for a "useable" oil port, you need to go to the oil filter housing. Oil pressure in the head is not great, especially at idle.

 

[Pasta_Ricer]

Oh that's good to hear. In the future I will be turbo'ing it. But which one is the feed and which one is the return hole?

I already have an oil pressure sensor connected to the place where the stock oil pressure sender unit would be and it's been working pretty well for about 8,000 kilometers now.
I will be investing in an oil cooler soon and was gonna use a sandwich plate. My oil gets extremely hot after ripping it a couple of times. Oil pressure at 3k RPM drops from 5.6 bars to about 4.4 bars after 2-3 pulls and takes a long long while to go up again even on the highway at a steady 120 km/h.

The 17mm and the small Allen next to it are to feed the turbo. People typically take oil pressure readings from the oil filter housing. The only reasonable way to run an air to air oil cooler is to run an ofh that has the proper provisions. For most builds, it isn’t needed.

 

[dwb]

But which one is the feed and which one is the return hole?

Return goes straight to the oil pan.

 

[Mech Addict]

It’s concerning that your pressure remains low for that long after WOT. Could be related to the oil temp, though. How do you know your oil gets hot, and how hot?
Most liquids decrease viscosity as the go up on temp. The variation depends on the nature of the liquid. Motor oil has some additives to combat this, but can’t eliminate it. Lower viscosity means less resistance through the bearings and such, and that translates to lower pressure at the pump.

 

[Pasta_Ricer]

It’s concerning that your pressure remains low for that long after WOT. Could be related to the oil temp, though. How do you know your oil gets hot, and how hot?
Most liquids decrease viscosity as the go up on temp. The variation depends on the nature of the liquid. Motor oil has some additives to combat this, but can’t eliminate it. Lower viscosity means less resistance through the bearings and such, and that translates to lower pressure at the pump.

I don't have an oil temp gauge, yet. I'm pretty sure it's the oil getting hot causing that as I have a new oil pump with only 8k km on it. The engine was overhauled completely and I even have the balance shafts deleted properly by my mechanic who really knows his stuff (specializes in Mercedes and Japanese cars). The head was a second-hand one with basically no use on them. Have changed the oil 3 times and I run 20W-50 as recommended by him.

And let me tell you that I really do run her hard
Usually 1st to 3rd gear pull mostly shifting at 6.5k-7k RPM, repeatedly.

 

[danl]

Oh that's good to hear. In the future I will be turbo'ing it. But which one is the feed and which one is the return hole?

I already have an oil pressure sensor connected to the place where the stock oil pressure sender unit would be and it's been working pretty well for about 8,000 kilometers now.
I will be investing in an oil cooler soon and was gonna use a sandwich plate. My oil gets extremely hot after ripping it a couple of times. Oil pressure at 3k RPM drops from 5.6 bars to about 4.4 bars after 2-3 pulls and takes a long long while to go up again even on the highway at a steady 120 km/h.

4.4 bar is 64 psi. That is still plenty at 3000 rpm. All oils thin out *significantly* when hot.

 

[Pasta_Ricer]

4.4 bar is 64 psi. That is still plenty at 3000 rpm. All oils thin out *significantly* when hot.

That is true, but aren't I burning the oil a bit?
I still need to attach an oil temp sensor to it. I've made a digital launch control system using an Arduino and I have an NTC thermistor that's tucked inside the fins of the radiator to get radiator temperature readings. I could reposition it somewhere to get oil temp readings, but not sure where to put it so that it doesn't directly touch the oil because I'm afraid of it contaminating the oil.