Oil in #3 exhaust port, what's up?

GIBSON · GIBSON's Garage

I just removed my 73 engine for it's 1000 mile service (just rebuilt this past spring). It's been running well, It was a full rebuild down to the main bearings. To my horror I found the #3 exhaust port saturated with oil (the others are dry) and an oil drip on the tip of on of the exhaust studs. What's going on? Ring failure?
The heads were all redone with new guides, so I don't think they are to blame. The spark plug was oil-soaked of course. Have not had a chance to check head stud torque but it was fine when I checked at 500 miles. Any ideas? Can't do a compression check as the engine is on the stand, I guess I could do a leak-down test... Man, this is not what I wanted to see. Am I over-reacting?

john walker's workshop · 08-27-2002, 08:57 AM

whatever test you do, will still require a teardown to find the problem and repair it, so you might as well get started. it's already on the stand, so pull down the one side. you'll know in about an hour.

GIBSON · GIBSON's Garage

Yea, I figured I was head that way. What do you think about pulling the entire right bank in one section (i.e. don't remove the cam-tower and individual heads) ? Seems like the odds are it's rings....

john walker's workshop · 08-27-2002, 10:04 AM

that's the way i do it. gut the chain housing, and then remove it, and pull the heads and cam tower as a unit.

Doug Zielke · 08-27-2002, 05:20 PM

Bruce, I'm thinking you might find a broken ring.
(Hope I'm wrong!)

TimT · 08-27-2002, 05:57 PM

Did you notice any obvious blue clouds following you around? blue w/ acceleration usually rings..... blue on decel usually valve stem seal or worn valve guides....

sounds like rings since the engine is still "fresh"

GIBSON · GIBSON's Garage

I'm thinking rings as well. I just did a leak-down test just to see what that showed and all cylinders are around 6% with #3 maybe slightly less. I know that to loose that much oil down the hole and have it be a broken ring it would have to be the oil ring and that would not show on a leak-down test.
I think the next thing I'm going to do is to look through the spark plug hole and see if the top of the piston is wet. Seems like that should tell me something. I can't imagine it would be dry if the oil ring was broken.
If it's wet, the bank of heads comes off for sure, maybe anyway.

speeder · speeder's Garage

Bruce, Did you rebuild it yourself or have someone else do it? Obvious where I'm going with this, if you had someone else assemble it, knowing you it was someone good, I'm sure that they will stand behind their work. If it was DIY, disregard remarks. Mine is about to be DIY.

Sean Hamilton · Sean Hamilton's Garage

Bruce, what about the Valve Stem Seal? - Could it have been omitted, faulty or incorrectly installed?

GIBSON · GIBSON's Garage

Sean, I thought about the seal as well. It's new, of course, installed by the machinist but it could have ripped. I can change it without removing the head by pressurizing the cylinder and compressing the spring to remove it and get to the seal. I just don't want to waste my time if it's really a broken oil ring.
I looked down at the piston and it is slighly more wet that the others but that could be oil coming back from the valves as they open.

Early_S_Man · 08-27-2002, 06:59 PM

Bruce,

Are you planning to use a borescope for the cylinder inspection tour? If so, be sure look down the intake stack, and see if there is oil on the back side of the intake valve.

I assume the shop that did the heads set up the spring heights and shipped you ready to install heads, right? I am thinking loose or ommited intake valve stem seal. Relatively easy fix.

What brand of rings did you use ... Total Seal, Deves, or Goetz?

GIBSON · GIBSON's Garage

Warren, yes the machine shop shipped the heads ready to install.
While the exhaust port is wet, the intake is dry as a bone. No sight of oil on the valve or the visible stem.
The exhaust valve and stem are soaked. If there was a broken ring, wouldn't it tend to soak both the intake and exhaust valves to some extent?
I have new valve guide seals, I can easily replace them, seems like the exhaust side would be a good place to begin.
The rings are Deves.
If there was a seal failure would it not be possible for some of that oil to make it's way back into the top of the piston giving it a slightly oil appearance?

john walker's workshop · 08-27-2002, 07:57 PM

another possibility is a guide loose in the head.

GIBSON · GIBSON's Garage

Ok, I replaced the exhaust guide seal, I doubt it was the problem but while I had the springs off I decided to install a new one.
I placed lateral pressure on the valve and could not produce any movement. The guide seemed tight.
I guess tomorrow night the heads come off and I'll take a look at the rings. I'm just not sure that's it but I don't know what else to check. Could the reason the exhaust port is wet and not the intake just be gravity pulling all the oil down? Seems like with the blow-by a broken oil ring could produce you'd see oil on intake and exhaust sides but maybe I'm wrong...
BTW, the whole time I had the #3 hole pressurized so I could compress the valve spring, the leak-down was reading 3%. At least the compression ring must be doing it's job.

Denis, looks like I'm the only one to blame on this one, I did the engine rebuild. At this point I just want to find out what's wrong and fix it. Maybe even learn something in the process.

Sean Hamilton · Sean Hamilton's Garage

Quote:

Originally posted by GIBSON
......Could the reason the exhaust port is wet and not the intake just be gravity pulling all the oil down? Seems like with the blow-by a broken oil ring could produce you'd see oil on intake and exhaust sides.........

How you mean - just on the #3 exhaust port? Is that possible?

Bruce, something seems screwy here?
I thought a broken cylinder "oil" ring would oil wet both the exhaust valve and stem AND the intake valve and stem.
It's only "The exhaust valve and stem are soaked" Okay, you've replaced the exhaust guide seal - so the original seal was good?
Did you check the "guide loose in the head"? Is it possible to check that the valve stem guide is seated home properly?

I'm intrigued (but i feel your pain) and can't wait now till "tomorrow night" - keep us posted and good luck.

GIBSON · GIBSON's Garage

OK, here's my working theory. Feel free to blast away if I'm crazy but here goes.

1. The engine was rebuilt and installed in late April of this year.
It took me until last week to get 950 miles on the car- (I know, you're supposed to drive these things...).
2. I may have overfilled the tank slightly at the 500 mile oil change, no overflow out the breather but more than half way up the dipstick.
3. The car sits at a slightly forward angle, i.e. the #1/2 cylinders sit higher that the #3/6 ones do. So, oil seeps down through the not completely seated rings and collects in the exhaust port.
I also noted a slight amount of oil in the #6 port as well, just not as much. The other ports are dry.

That being the case, put the engine back in the car and drive it hard for a while, monitor the oil usage and see what happens.
Make sense to anyone but me?

Early_S_Man · 08-28-2002, 11:04 AM

Bruce,

Is it possible that the #3 and #6 oil control ring gaps are at
the lower 120° section of the pistons?

I recently posted my personal theory on the 'smoke on startup' phenomenon ... so, your explanation rings true, except for the 'collecting in the exhaust port' ... part of your premise! My belief is that any oil entering the exhaust port drips/runs directly down into the heat exchanger. So, you may want to change the #6 exhaust valve stem seal as well!

As far as the 'quandering' about oil contamination of the intake port ... reversion would contribute to the possibility, but the mass and 'extraction' flow of the incoming intake charge at overlap would seem to minimize the possibiility ... to me!

GIBSON · GIBSON's Garage

Warren,
The rings are oriented as per Deves instructions, is some ring rotation expected as time goes by?
Yes, I may change the #6 seal as it's easy to do at this point. I used the seals supplied in my gasket kit (Goetze?) They were slightly different than the seals installed at the machine shop but I doubt that's a problem.
I do think that the intake air flow pressure would tend to keep the intake side cleaner and that's what I have found.

So, I think that the combination of a fresh engine, a bit too much oil, rings not fully seated (probably not enough aggressive driving on my part, at 950 miles I have not gone over 5200 rpm) and the engine sitting too much has resulted in this situation.
If I do have a broken oil ring I could do damage by driving the engine. However, I think now that things are pointing to an oil collection probem...

jabb · 08-28-2002, 02:06 PM

Gibson:

When you check for movement in the exhaust guide from side to side was the valve compressed . The best time to check for movement is when the valve has tension applied.

Early_S_Man · 08-28-2002, 02:34 PM

Bruce,

Another concern may be those restriction fittings for the cam tower oil supply ... they may have 'upped' the supply volume and pressure to the case 'squirters' at low revs and temperatures ... enough to be causing an overabundance of oil for the rings to handle during break-in! Maybe time to put the old ones back in ... for the mean time, at least until 5K miles or so, and certainly until this 'oily exhaust port' problem is in the distant past!