Scored Camshaft Lobe

[rod_ontario]

The camshaft on the intake side of the #3 cylinder of my 92Q is worn. What would cause this?

[technoman]

low oil pressure would be my guess. Im sure the shim looks worse.

[rod_ontario]

Would the hydraulic lash adjusters cause this? Leaking oil and dry at startup?Have an engine (Original engine) with a blown head gasket that my wife drove until the engine was thoroughly steam cleaned and destroyed. The white smoke coming out the back in –40-degree weather on a winters day in northern Canada, should have been a good indicator of impending doom. Denial is an expensive luxury?What I was thinking of doing is taking the cam from that engine (On visual inspection it appears fine) and replacing the scored one. Am I out to lunch on this coarse of action?

[technoman]

Is that the only scord cam lobe? Or is all of the lobes scored?

[rod_ontario]

All the others seem fine; it’s the bottom of this particular lobe that is damaged.

[technoman]

Replace the camshaft lifter and shim make sure oil is getting to the lobe.

[rod_ontario]

I don’t see a shim in the schematic, or maybe you are using terms I don’t understand. I’m not a mechanic, but the members of this board have been a huge resource.

[technoman]

The shim is hard to make out because it sits on top of the lifter.so it looks like it's apart of the lifter. the lobe ride's on the shimif you pull out the lifter you will have pulled out the shim as well. the top of the lifter is the shim.

[rod_ontario]

Thanks technomanIs there a trick to checking if the oil is reaching all critical parts – such as manually spinning the oil pump?

[technoman]

I think you should ask Q45tech. He is very good with the nissan V8. I can't really see the pic of your rocker arm. It seams to me that the cam is dry at the lobe and rocker making it pit as you can see in the first pic of the cam lobe.

[rod_ontario]

I read this site daily and am truly amazed at the quality of info that is posted - Like an online mechanics tutorial!I was a little bit bashful about putting the image of my varnished engine on the site out of fear of getting a virtual beating from Q45Tech. Blaming it on the previous owner!The picture of the lifter is off my old engine. I have not removed the faulty one as yet.P.S. There's 240000 K on the engine.

[Professor_Mike]

The picture you show is the roller rocker arm. On one end of this is the valve, other end the rocker pivot or hydraulic lash adjuster. There are no shims on this vehicle. I would suggest reassembling with the old parts and spinning the engine over to check for oil flow. You should remove the fuel pump fuse under the dash and disconnect the 3 connectors at the right rear of the engine to remove spark and fuel. If everything looks OK you could replace the cam, possibly a used one to save money. I would use the rocker arms to match the cam since you have both.

[rod_ontario]

Thanks Professor_Mike – This was the advice I was hoping for. Common sense suggested this coarse of action. However my common sense has gotten me into allot of trouble over the years when I neglected to consult those with more knowledge and experience.I also posted a note asking the Q45Tech if the VTC Assembly is adjusted for the particular motor that it is installed in or if it is adjusted at the point of production.

[Professor_Mike]

The VTC is available separately as a unit. This would lead one to believe that the VTC has the necessary specs to match any camshaft. Give INFINITI's low tolerances this is sufficient.

[rod_ontario]

Thanks By the way, I have the motor out on my workbench - rear seal was leaking!Semi retirement allows the semi knowledgeable the time to get into a whole lot of trouble. In fact, just last night a middle aged guy in the neighborhood was working on his breaks and had his car fall on him. Carelessness and lack of knowledge cost him his life!!

[Q45tech]

Natural selection at work........anyone who uses jack stands has my prayers. It is not frequent but cars have fallen off of dealer lifts.

The VVT solenoid just shuts off the oil pressure at 4600 rpm so the cam returns to the 0 degree open position vs the 20 degree BTDC advanced position.

Somewhere above idle the oil pressure is enough to advance the cam.....the Consult has a manual on/off test mode....but it is listen for the click whereas the 97+ have a sensor to make sure it happens!

Generally the cam is designed for great idle and good power up to 4600 to enhance torque......it is not necessarily optimum for above 5500-5700-6000 rpm.......more exhaust duration [248] and overlap is needed as only 8 degrees above 4600.Each extra 10 degrees on exhaust will move peak torque up around 500 rpm which is what happens when the cams slip a tooth the exhaust then closes at 18 ATDC.......but the drivers side is usually the only one affected.

[rod_ontario]

Thanks Q45TECH,As a Firefighter, I have seen many examples of natural selection.One in particular was another firefighter who was putting a tire on his car and the jack slipped trapping his hand between the tire and wheel well. Not a big deal except for the fact that he was in an unheated garage and it was 35 below and no one around. Would have frozen to death, if not for the timely arrival of his wife

[DAEDALUS]

That's horrible about your neighbor! I can only wonder what it was he was doing on his brakes that would put him in harm's way like that. Maybe had his head between the rotor and body? Gory. My girlfriend has conceded that when we buy a place of our own, the first thing I can have is a lift in the garage and a compressor. Till then, it's jack stands with the jack as a back-up.

[technoman]

Man that seams scary. I just did a 4 wheel brake job on a 91 300z with jack stands. Man i hate those things!

[911/Q45]

I got a slick item called a SafetyJack about 10 years ago. It incorporates the stands into the jack so you can jack it straight up, at the spot selected, and leave the stand there. No more jacking under the oil pan or differential and then placing the stand. Has anyone else seen one of those? They don't make them any more and I regret not getting a lower stand option for low slung cars. If anyone knows a source for those, I'd sure be interested.