What are these???

[TurboBlue]

ok, first, i know this isnt exactly a problem, but im rebuilding my motor right now and just had a question.

Before my motor threw a bearing, we were messing around with it at work. We started the car with the valve cover off and all of a sudden, these 2 litle holes shot oil 2-3 ft in the air. So we plugged them temporarily and we then noticed that every single rocker arm was oiling each cam lobe...

These holes are on the cam gear side of the head, right ontop of the two oil runners...

I've gotten a few different opinions, some being that they are there for air bleed, others being that putting a hole in your oiling system is stupid and drops pressure. Another statement was that with the 1st generation lifters (with the small hole), people kept floating valves and bending them on pistons because the liftrers couldnt collapse quick enough with the small hole. So rather then keep replacing heads, mitsubishi put these holes here as a quick and cheap fix. Any imput would be greatly appreciated. Thanks

PS, sorry for the long post...

 

[Sean485]

Thats the end of the lifter oil feed galley, if those holes werent there then the last couple lifters might be getting pressurized air instead of pressurized oil and since the lifters basically oil the cam lobes your cam would be getting poor lubrication too. Leave them there, they're designed to be there

 

[GTM]

...
We started the car with the valve cover off and all of a sudden, these 2 litle holes shot oil 2-3 ft in the air. So we plugged them temporarily and we then noticed that every single rocker arm was oiling each cam lobe...
...
I've gotten a few different opinions, some being that they are there for air bleed, others being that putting a hole in your oiling system is stupid and drops pressure. Another statement was that with the 1st generation lifters (with the small hole), people kept floating valves and bending them on pistons because the liftrers couldnt collapse quick enough with the small hole. So rather then keep replacing heads, mitsubishi put these holes here as a quick and cheap fix. Any imput would be greatly appreciated. Thanks
PS, sorry for the long post...

Oh, that's always exciting starting the car with the cam cover off. How long did you let it run?

I'm concerned about the pressure > actually the lack of pressure. When possible I use a vari speed electric drill and spin up the oil pump which then lubes everything in advance of cranking if the enging has been apart. My experience has that it will throw oil a good 6-8 feet, my point was that you had to plug the holes to get pressure. These holes are part of the pressure regulation which is set aroung 25-35psi so it doesn't flood the valve stems and all the other motive parts.

I've not heard reports of the floating valve problem you mention but that doesn't mean it's not so. I will ask you to think through the action of the cam lobes, cam followers, and the hydraulic adjustments. Valve float occurs when the engine is turning sufficiently fast enough that the lobe strikes the valve so hard that it is no longer following the cam profile it is thrown off it's seat like being hit with a hammer. It exceeds the lobe lift and sequence, if the piston is present it will collide but all the bent valves I've seen are bent not at max lift but further close to the valve head. There would be dents in the center of the piston had that happened which don't exist. The piston is on it way down and the valve is now caught up with the cam lobe. If there was any opportunity for the lifter to cause the problem it would be in the last few degrees of ratation if the lifter was too far extended it could cause the intake to foul on the exhaust but that would leave a scrape mark on the top of the valve and I've not seen those either. What we do see is the result of cams jumping time and then the valves and pistons collide when they are out of sequence. That's a quick rundown on the valve situation.

Anyway, have you done anything to improve the oil pressure or at least kept a check on it?

Cheers,
Gene

 

[TurboBlue]

well with the new motor a new front case, oil pump gears, and oil pick-up will be installed. So as far as improving oil pressure thats about all. Motor isnt done yet however, so i'll have to just wait and see...