Oil leaking out of spark plugs

[Shane nakaya]

Oil is leaking out of the spark plugs in my 620. Not sure why the oil is leaking but it is causing fouled spark plugs 

[datzenmike]

What plugs are you using? Should be NGK but you don't have the year of your truck in your profile so not sure what plug type you need. If you have NGK plugs did you get them from Amazon? I wouldn't but them there, to many counterfeits sold.

 

 

Is there any blue smoke coming out the tailpipe? Have someone follow you if you are not sure.

How many miles to the quart of oil do you normally get?

Do a compression check. This will give a rough indication of the wear on the engine.

 

Excessive oil consumption will foul the plugs and they will miss fire and not burn it off. The wetness could, I suppose, squeak past the threads. 

 

Oil can only get into the combustion chamber past worn oil control rings or worn out valve guide seals.  

 

 

[banzai510(hainz)]

all my olddatsun did this. I just ran them untill i finally build the motor but it wasnt a huge proplem

[Stoffregen Motorsports]

How many miles on the motor? Just curious really, as this means nothing in itself. High mileage in an antique motor like the L series, it's probably worn rings, valve guides and valve stem seals all in one.

[datzenmike]

Should have a blue cloud chasing it.

[Shane nakaya]

11 hours ago, Stoffregen Motorsports said:

How many miles on the motor? Just curious really, as this means nothing in itself. High mileage in an antique motor like the L series, it's probably worn rings, valve guides and valve stem seals all in one.

Motor has 176,000 miles on it

[datzenmike]

If the engine is looked after the L series is more than capable of that mileage but after neglect by the previous owners 175k is a lot.

[EDM620]

On 6/6/2023 at 10:21 AM, Stoffregen Motorsports said:

How many miles on the motor? Just curious really, as this means nothing in itself. High mileage in an antique motor like the L series, it's probably worn rings, valve guides and valve stem seals all in one.

Valve stem seals are dirt cheap. They get old and crack. Worn oil rings is a probable candidate. When do you see the heaviest blue smoke? At start-up or running and under load? Compression test is needed.

[Shane nakaya]

On 6/8/2023 at 6:40 PM, EDM620 said:

Valve stem seals are dirt cheap. They get old and crack. Worn oil rings is a probable candidate. When do you see the heaviest blue smoke? At start-up or running and under load? Compression test is needed.

Most likely o rings, no smoke upon running to startup

[KELMO]

On 6/5/2023 at 6:30 PM, datzenmike said:

How many miles to the quart of oil do you normally get?

Priceless Ratsun question.

[datzenmike]

If you get a puff of blue on start up, likely the valve seals. Oil runs down the stems over night and waits for start.  Easy enough to change and they are relatively cheap so if it's more the rings this isn't the end of the world.. Take valve cover off and the plugs out. Get a piece of nylon rope 3/8" and a few feet long with a big knot in the end. Set the engine on the compression stroke, both valves closed and back the engine up 1/4 turn before. Stuff a few feet of rope in plughole and hand crank the piston forward compressing the rope against the valves so they can't move. I would not advise using the starter for this. Once secure you have all the time in the world to remove the valve springs and old seals and replace with new seals. No need for electricity, compressor, hose or fittings, hell you could do this on the side of the road, leave over night and finish in the morning.

[EDM620]

On 6/11/2023 at 7:43 AM, datzenmike said:

Stuff a few feet of rope in plughole

This is an old mechanics trick and works excellent, one cylinder at a time. Best rope to use is the stuff for clothesline - it's soft and won't leave bits behind. Avoid using nylon rope.

[Stoffregen Motorsports]

That shit'll burn up and get shot out the exhaust anyway.

20 hours ago, EDM620 said:

This is an old mechanics trick and works excellent, one cylinder at a time. Best rope to use is the stuff for clothesline - it's soft and won't leave bits behind. Avoid using nylon rope.

 

[Stinky]

You do not want to use Platinum, or any high-dollar plug if you are fouling plugs.  

 

You want to use a standard copper plug.

[EDM620]

You could run a slightly hotter plug to help burn the oil off. 

NGK.com: What is a Spark Plugs Heat Range?

 

[yenpit]

In case you aren't quite clear.............oil around spark plugs while tightened IN PLACE, can be as simple as a leaking valve cover gasket.  It just runs down the side of the cyl head & collects around the plugs.

 

If you are ALSO oil fouling the plugs, then it is likely an internal engine wear issue.  As stated above, try the rope in the spark plug holes in order to change out the valve stem seals FIRST, cuz it does not involve rebuilding or replacing the engine!  FYI by stuffing the rope in the spark plug holes & HAND CRANKING the engine until it brings that piston all the way up in the cylinder bore, you are holding the vales UP IN PLACE from the inside (with the bundled up rope in the combustion chamber), so you can replace the valve seals under the valve cover.  You will need to remove all of the rocker arms, lash pads & springs ONE AT A TIME............KEEP THEM IN EXACT ORDER, EXACTLY WHERE THEY CAME OUT OF!!!!!!!!!  If you mix up the rocker arms & lash pads, you will need to re-set all of the rocker arm to cam lash specs!!!

 

Also replace the spark plugs with NGK copper plugs, as mentioned before!

 

If new valve seals do not work, then you likely have worn and/or broken piston rings, which requires a full engine rebuild or replacement.