Oil Port under CAS (Cylinder Head)
 

Hi,

The prior owner of my car used the Oil port below the CAS on the BP head to install an after market fuel pressure guage. It looks like a 10mm x ? thread (Can anyone confirm this). I'm preping for my MegaSquirt install and it would fit due to the size of the sender, but this had got me thinking.

Why are we not using this port as an oil feed? Does this port lack the pressure to supply our turbos? I noticed it always has pressure on the gauge :)

Does anyone have an old head kicking around with this plug in it? I don't have the plug and need to block the hole.

Or... Does anyone know the thread of this hole so I can purchase a plug. (I'm guessing 10mm x 1mm)

Let me know your thoughts.

if it's 10mm it's either 1.50 or 1.25. would cost you like .50 to get both.....

I'm unsure of what port you are describing, care to find a pic?

I just thought.. I could be 1/8 BSP also. It looks so close to a 1/8 NPT.

http://members.aol.com/solomiata2/99head4W.jpg

It is the port right under the CAS block off.

Do you know what the oil pressure is like there? I'd definitely check that against what's down at the block. If it were feasible, then you'd have to wonder why Mazda didn't use it on their OEM turbos. :dunno:

I would assume not because of it's location.

Oil Presure is always above 20psi at idle, and much higher with RPM according to my Blitz gauges. I'm really surprised this port is not used. There has to be a reason. I wonder if Corky will see this and chime in.

Where does mazda source the oil for their factory turbos on these engines, namely the mazdaspeed miata?

i wouldnt feel too good taking oil feed from the head
IMO it just looks like it will take a long time for the oil to reach the turbo especially if the passages are somewhat contaminated and flow is even more reduced
i do wonder if anyone has tried this or is willing to...

Sam, not sure on mazdaspeed, but my 94 block has a plug in the block on the hotside meant for oil feed

Oil Pressure starts to read on the gauge almost instantly when I start the car, plus anyone using a GT series turbo does not need a lot of oil for the supply of the turbo. (The reason they recommend restrictions).

Does anyone know the thread of this? Or have I just opened a new can of worms.

Though, that's a good point. You've got to wonder if pulling from the head is not going to hurt it. That source is the main feed to cams. The block source is one of the largest oiling channels in the engine post pump. Don't you have a reputation for "opening cans of worms"? ;)

on the 99-00 head? you mean on the back?

http://members.aol.com/solomiata2/99head4W.jpg

or under the actual electronic sensor on the intake cam?

The factory gets oil press down under the intake manifold next to the filter. I teed my turbo's oil feed AND oil pressure sender in there with a BSP to NPT adapter and AN- tee.

On the back of the head under the CAS hole is where the prior owner had his Oil Pressure gauge.

Yeah.. I don't know how to think INSIDE the box.. Only OUTSIDE for me...

Im sure there is a good reason why we arent sourcing it from there, I am sure you arent the first person to find that port.

i dunno, i say it's fine. somewhere you can probably find an oil passage map and determine if it's a bad idea.

The miata FSM has a oil passage map. id take a screen shot but im not at home.

That is how the BeGI kit i am installing does it. That being said though this is an interesting idea. It would make the oil feed to the turbo much, much shorter. This could work as long as there is room to get a 90 deg fitting in between the head and the firewall, which I think there is since the CAS is big and fits in there; I added a CAS to my '99 for the MS install.

yeah the CAS is like an inch and a half thick and has more room behind it.

My mates evo takes oil feed from the same place. I wouls suggest that the only reason people don't use it is because you can get a cleaner feed from nearer the source easy enough on these motors.

When rebuilding my 1.6 I noticed the oil passage in the block that feeds the head has a oil restrictor in it that would limit the volume of oil to the head. I would be afraid to use the port on the head for fear of starving the head.