Oil on top of pistons

[Los_Control]

To be honest, I think pulling the head is the next step. It is obvious there is oil in the cylinder .... it is a internal problem.

 

You will need to actually open it up and look.

[Ivan_B]

Okay, my "tomorrow" might've been a bit too optimistic, since it take some time to disassemble this engine. The head is off. I did not notice any obvious issues, at this point. I'll replace the stem seals, since I am in there, but will probably be able to leave the valves as is, assuming that they are not leaking. The headgasket also looks normal. Thus far, It seems that the rings are the only thing left. It is somewhat unexpected that the problem only affects one cylinder, though 🙄

 

[Los_Control]

It would be nice to replace the seals and find a obvious leak.

No question it is a small high performance Hot Rod engine that runs under high stress.

 

I wonder if it would do any good to put the plugs back in the head and then fill the chambers with gasoline and check for leaks?

The intake valves on #3 look pretty clean, #4 has a little smudge and #1-#2 are filthy .... seems exhaust valves are always black and sooty, while intakes are clean ... on a good running engine.

 

I wonder if the valves are leaking, can we lap the newer modern engines the same as we could the older engines .... to get the valves to seat?

Or do the seats have to be surfaced with a seat cutting tool?

[kencombs]

I am not familiar with that engine, but some of the newer, smaller, especially turbo-charged engines have issue with the PCV systems that cause similar things.   GM's version especially with the intake changing from vacuum to pressure they have difficulty with reliably managing the fume and oil flow.

[Los_Control]

I looked at your video you shared .... right about the 9 minute mark he was talking about a contraption that operates off of oil pressure and controls the lift/duration of your intake valves .... All I know is he said they go bad and are expensive ....  just something I would want to learn more about.

 

 

[Ivan_B]

4 hours ago, Los_Control said:

I wonder if it would do any good to put the plugs back in the head and then fill the chambers with gasoline and check for leaks?

Do you mean to put the head upside-down and pour some liquid on top of the valves? Sure, this will be part of the testing I'll do. Another part will be to fill the intake/exhaust ports with liquid and see if it leaks out through the valves

4 hours ago, Los_Control said:

seems exhaust valves are always black and sooty, while intakes are clean ... on a good running engine.

The intake valves are at the bottom on my image. The intake valves are clean from the back side (washed with injected gas spray) while dirty at the front. The exhaust are cleaner at the front (due to higher working temp?) but are very dirty on the back. I'll need to clean the back of the valves and the exhaust ports, which is a lot of work I am not looking forward to 🫠

4 hours ago, Los_Control said:

I wonder if the valves are leaking, can we lap the newer modern engines the same as we could the older engines .... to get the valves to seat?

Sure, these can be lapped in the usual manner, to a certain point, until you need the new valves/seats 😅

1 hour ago, kencombs said:

I am not familiar with that engine, but some of the newer, smaller, especially turbo-charged engines have issue with the PCV systems that cause similar things.

That is true, there is a known condition where the PCV will push some oil into the intake. But my oil appears to be coming from within the combustion chamber itself, unfortunately. The intake manifold is relatively clean, and the issue mainly affects the #1 cylinder, which is literally filling with oil quite rapidly. Some of the other ones are a bit oily too, but not enough to foul the plug and generate a misfire.

1 hour ago, Los_Control said:

right about the 9 minute mark he was talking about a contraption that operates off of oil pressure and controls the lift/duration of your intake valves .... All I know is he said they go bad and are expensive ....  just something I would want to learn more about.

Yes, this is the dreaded multiair brick, which controls the variable valve timing. Mine still works alright and appears to be in good condition. It is sitting underneath the valve cover and has no direct connection to the combustion chamber. It just drives the intake valves, in the usual fashion.

[kencombs]

IF the oil is coming from the intake, either past stems, or in the intake air via the PCV, the back of the valve heads should show signs of that.   I really can't believe that much oil enters the cylinder past the rings with the compression you have, unless the oil ring has failed.   In that case I'd expect to see signs of that on the cylinder walls.

[Ivan_B]

11 hours ago, kencombs said:

In that case I'd expect to see signs of that on the cylinder walls.

True... And the walls look good... 🙄

I don't know, the back of the valves looked dry to me (images shared on the previous page). I'll replace the seals, anyway, already got the valves removed... Also, noticed first problems when cleaning the head: cylinders 1 and 2 have signs of damage from foreign items inside the chamber. No major failure but something was definitely going on in there, at some point 😑 

I have yet to remove and inspect the pistons + rings.

[Ivan_B]

Just a little update: ordered bout $400 in parts (gaskets, rings, tappets) and started putting things back together.

Here is a picture of the damaged head surfaces.

[Sniper]

I wonder if that's impact damage or erosion? Many years ago I was fooling around with a Carter AFB on top of my 318 and I dropped the accelerator pump check ball into the intake. It made its way into one cylinder and I had a bunch of nice little round dents in the top of the piston. But I never did find that ball it must have blown out the exhaust eventually.

[Ivan_B]

This is impact... I also did not find anything except the markings on the head and pistons. IT was something hard, irregularly-shaped (all marks are different) and quite large. I am thinking - maybe a plug electrode tip? 😒

[Los_Control]

also possible just a casting flaw from birth? .... seems like all the damage is on one side and not the other ... on both chambers. Like they were low on sand on that side.

 

What I see is something that makes you go Hmmm🤔 .... not anything to stop it from going back together.

 

Any idea where the oil was coming from?

[Sniper]

1 hour ago, Ivan_B said:

This is impact... I also did not find anything except the markings on the head and pistons. IT was something hard, irregularly-shaped (all marks are different) and quite large. I am thinking - maybe a plug electrode tip? 😒

 

I was wondering if it was carbon from the intake valves getting in there, but your ports look pretty clean.  DI engine are known for carbon build up on the back side of the intake valves.

[Ivan_B]

This is a regular injection. The intake ports are washed with gas, the exhaust ones had plenty of carbon which was very difficult to clean. Just discovered that #1 both exhaust valves are bent. I guess I should've checked all of them right away 😒

[Ivan_B]

Things are moving slowly. The 2 new exhaust valves are arriving today, and it is going back together 😏

 

[Sniper]

Did you find were the oil was coming from? 

[Ivan_B]

On 2/22/2025 at 5:25 PM, Sniper said:

Did you find were the oil was coming from?

I most certainly did not. The piston rings were okay, despite the end-gap being out of specs. The head gasket also seems okay. The only plausible explanation, at this time, is valve stem seals. These appeared somewhat well-used. Speaking about valve stem seals - I managed to waste all 16 of them, last week. I meticulously put them on, and then realized that I forgot to install the valve spring spacer washers, which go onto the stem and do not fit over the seals. What an unintelligent thing to do... 🙄😒

 

I even managed to take one of them off, almost without damaging it in the process, but figured out that I do not want to take any chances with these. So I had to order another set. Hopefully my new-new stem seals will come tomorrow and I'll finally put this thing back together.

[Ivan_B]

The engine saga continues...

I wish I had some good news to share, but I don't 😅

I installed the new stem seals and put everything back together. I wanted to check compression right after the head went back on, but the starter would not spin with half the engine missing, and I did not have time to mess with it. So I continued the assembly process. Later on, I determined that even if it did spin, I would not be able to test compression without the valve-train assembled anyway 🙄

Long story short - the engine is assembled and I have 0 compression on all 4. After hours of troubleshooting, I determined that my new hydraulic tappets are too high and keeping the exhaust valves partially open. What a bunch of nonsense 😒

 

I spun the engine for quite some time but the tappets are not bleeding down. And there is no way I can start the engine, like this, to warm them up either. Thus far, it looks like i have to pull the cam and manually bleed them (squeeze some oil out) so that they have a chance to adjust to the proper height.