1975 280Z engine questions

[shadesh]

I have a 1975 280Z with a L28 engine... N42 head.. fuel injected. Everything on the car is stock as far as I can tell. I bought this car not too long ago.

I found that there was oil on all six spark plugs.

What would cause oil to be on the plugs.?? Worn piston rings or worn valve seals or guides or maybe high engine case pressure.??

Can high engine case pressure cause oil to go down the combustion chamber???

The reason I ask is because the oil pressure guage reading goes above the middle ..

I wanted to do a compression test for all the cylinders but I don't know what results I should expect.

Does anyone have any numbers you could throw at me in terms of what reading I should expect.??

[ekaphoto]

First of all I am far from being knowledgable.

Was the car sitting for a long time before you bought it? If so someone may have shot oil down the spark plug holes to keep the motor from rusing and seizing up. Used to be a common practice with motorcycle riders for long time winter storage.

also are you sure it is oil?

[shadesh]

The car sat for a few years but I don't think the previous owner was "storing" the engine correctly by shooting oil down the plug holes.

Yes, The stuff on the plugs is fresh motor oil.

[Arne]

You may have gunked up oil control rings if the engine sat unattended for years, and then not properly prepped before firing it up. Check out this thread:

http://classiczcars.com/forums/showthread.php?t=22619

In particular, it may be worth doing the ATF in the cylinders thing to attempt to free the rings up.

[shadesh]

Thanks fellas. I will pour a couple of ounces of ATF (automatic tranny fluid) in the chambers and crank it tomorrow.

Any idea why the oil pressure reading is so high. It goes up as I rev up the engine...

Also, does anyone know what sort of compression reading I should be getting out of each cylinder. ??

Thanks again guys.

[d240zx2]

Anything around 150 should be pretty good. BUT...

If you do the test incorrectly, you'll get a false reading. First, remove all plugs and disconnect your coil wire. Second, wedge the throttle wide open. Third, crank the engine sufficiently to circulate oil. Fourth, take your reading.

Others may have variations on this, but it'll get you your answer.

Based on your earlier post, I don't think compression is your problem. I'd look to valve seals first, then rings.

Regards,

Frank

[shadesh]

Thanks Fellas,

I think I will start with assuming that the valves and rings are gunked up.. and begin by cleaning those out first. ..followed by a valve adjustment and then do the compression test and see if there is still oil going down the chamber and soaking up the plugs. This is gonna be a looong weekend. Thanks again. This forum is very helpful.