Spark plugs: seven tan and one nasty black

[Chuck]

My Genesis 427 side oiler, with a Holley 850 CFM carb, has 2500 miles, so I decided to change the plugs. It runs great - no complaints in that department. Seven of the plugs were a nice dark tan color. No significant carbon or oil. But one plug was black and grimmy. The car uses about a quart of oil in 300 - 400 miles. No oil leaks whatsoever (hard to believe!). When first starting up cold, it puts out a bit of black smoke, but once warmed the exhause iss clean. Any ideas why? Should I be concerned about that one nasty looking plug? Should I be patient and hope that it is a 'breaking in' issue that will resolve? Valve guides? Rings?

Tearing down an engine is not on my wish list.

 

[Neal]

Might be worth performing a leak down test. Rings, guides or seals are the most likely candidate.

 

[Paul Thompson 'Hooligan']

All stem seals in place? - one possibly lifted up the valve?

 

[Gordon Levy]

Chuck, what heads, cam, intake? Which plug?

 

[Jac Mac]

On an FE chances are its the intake manifold/gasket,porosity in the head/manifold area or some over zealous porting in the area where the oil feed goes thru head to rocker shafts. At least you know which cylinder which narrows down the search. If your running the PCV system it could be simply a case of having that plumbed into one runner rather than the plenum or a lack of baffles in the rocker cover.As pointed out a stray stem seal could be the culprit also.

Jac Mac

 

[Chuck]

Thanks for all the feedback. It is reassuring to now there is so much support out there for someone with little experience working inside an engine. Some responses to points raised::

The parts:
1. Autolite 3924 plugs
2. Edelbrock head 60069
3. Edelbrock dual plane perform intake manifold
4. Edelbrock cam, 7106
5. Genesis block, displacing 468 cc. Built per Genesis specs.
6. Holly 850 CFM

I checked the coolant – it is the same crisp, clear pink color as the day it was poured in six months ago.

Not running any PVC valves. Breather caps on both valve covers

Drove the car again tonight. It just runs great. No strange sounds coming from the engine, no problems with acceleration, no wisps of black or blue smoke from the offending side.

So here is my plan:

1. Carefully monitor oil consumption, rather than just guesstimating. I have been adding a cup here and there rather than letting it get down a quart. So my estimate of oil consumption may not be accurate.

2. Pull the new plugs and check them in a week or two after I have some miles on them. Perhaps it was a plug problem. (Hope springs eternal).

3. If the new plug in the suspect cylinder is black and grimy, then I will pull off the valve cover, do a vacuum check, and pursue some of the avenues suggested, and get back on this forum for more advice!

I guess I am in denial. It is a new engine, decent quality parts, low mileage, and just runs too good to need a major repair. We will see.

 

[flatchat(Chris)]

I'm with Jac -- see if there are any loose intake manifold bolts

 

[Dimi Terleckyj]

Hi Chuck

I know you say that the motor runs great but I would be concerned with the amount of oil being used in such a short number of miles.

If the motor is so new the oil usage should be negligable in such a short time.

This amount of oil usage and the grimey plug indicates it is being burned and is bypassing either seals or rings.

Dimi.

 

[John]

Thanks for all the feedback. It is reassuring to now there is so much support out there for someone with little experience working inside an engine. Some responses to points raised::

The parts:
1. Autolite 3924 plugs
2. Edelbrock head 60069
3. Edelbrock dual plane perform intake manifold
4. Edelbrock cam, 7106
5. Genesis block, displacing 468 cc. Built per Genesis specs.
6. Holly 850 CFM

I checked the coolant – it is the same crisp, clear pink color as the day it was poured in six months ago.

Not running any PVC valves. Breather caps on both valve covers

Drove the car again tonight. It just runs great. No strange sounds coming from the engine, no problems with acceleration, no wisps of black or blue smoke from the offending side.

So here is my plan:

1. Carefully monitor oil consumption, rather than just guesstimating. I have been adding a cup here and there rather than letting it get down a quart. So my estimate of oil consumption may not be accurate.

2. Pull the new plugs and check them in a week or two after I have some miles on them. Perhaps it was a plug problem. (Hope springs eternal).

3. If the new plug in the suspect cylinder is black and grimy, then I will pull off the valve cover, do a vacuum check, and pursue some of the avenues suggested, and get back on this forum for more advice!

I guess I am in denial. It is a new engine, decent quality parts, low mileage, and just runs too good to need a major repair. We will see.

Chuck,

I would run a compression check - I used to fool around with big block Fords. the compression check gauge screws into the spark plug hole so you don't have to remove any valve cover gaskets. You simply screw in the gauge, disconnect your coil so the engine won't start, and let the starter turn the engine over for a few revolutions. Judging from the description, it sounds like a valve might not be seating properly - check the compression on all eight cylinder and record the data. If the compression is the same for all cylinders, then you are in seventh heaven - the problem is more likely a bad valve seal.
I would check the compression with the engine hot and cold!

Good luck and keep us posted!

John

epper:

 

[Jac Mac]

Chuck,
While I hope your problem is as simple as a 'Dud' plug or lead, I would suggest that you eliminate the possibility of oil ingestion in that one cylinder via manifold/stem seal sooner rather than later. The thought that perhaps 75% of the oil consumption may be in 'that' cylinder should raise concerns of possible detonation & or ring/bore glazing. I am sure that you dont want to go thru the total engine rebuild that either of these conditions will lead to! To continue to drive it with this problem wont make it better.

Jac Mac

 

[Howard Jones]

I had a 302 SBF (X alum heads) with one of the EGR plugs missing. The spark plug in that cylinder was black also. Installed plug all well. I don't know if yours heads have these. It is a quick check/fix however.

Thereafter you must post compression data so we can help further.

Next cheepest fix, intake gasket on that head. BE CAREFUL tightening up intake bolts on alum heads. Tighter is NOT better!!!!!!

 

[Chuck]

Thanks for all the input. I am going at this slow. So here is a bit more info.

I have driven another fifty miles or so since changing the plugs. It runs just fine. Pulled a couple of plugs tonight and the problem cylinder is already getting grimmy and the other is slightly tan and dry. So the problem was not something simple like a bad plug.

But what was interesting was the puddle of oil at the spark plug opening. All around it was dry. Oil only in the spark plug hole. The threads were oily the full length.

I took pics of the original plugs, one good one and the bad one. Also some pics of the oil around the plug hole. Any thoughts?

 

[Jac Mac]

Chuck,

In your second photo it is either #2 or #7 cyl that has the problem, at least that eliminates the possibility of oil from the rocker shaft gallery being the problem ( unless there is something really crazy going on ) as the oil feed is above #3 &#6.

It's fairly obvious that quite a lot of oil is being introduced somehow and what you see of oil being forced up around the plug threads etc is common in this type of situation as that plug will not be firing full time in order to burn away all of the oil.

Along with all the suggestions so far the valve stem seal & or intake gasket are the most likely culprits- I dont know what the warranty situation is with your engine builder, but would suggest that you contact him sooner rather than later, If its a stem seal its a relatively simple matter to pull the rocker cover & shaft assy & replace the seal using a KD tool & a piece of nylon rope /cord. I know that if I had built the combo for you I would prefer to find the cause of this before it develops into a major problem.

Jac Mac

 

[Gary Kadrmas]

I agree with Jac Mac.....................

Process of elimination..........................I would start with the valve stem seal, and proceed accordingly after that. It is not uncommon in the assembly process to damage a valve stem seal during the assembly phase. But if you do the seal, the outcome may solve the issue.

I wish you luck with your efforts, and hope you find the answer soon.

 

[Chuck]

All of the good advice has not been ignored. I finally got around to doing the compression check today. Recall that plug #2 has been the culprit. The engine was thoroughly warmed after a good forty mile drive when we checked the compression. The results:

Cylinder Pressure
1 . . . . . . .165
2 . . . . . . .175
3 . . . . . . .170
4 . . . . . . .165
5 . . . . . . .170
6 . . . . . . .170
7 . . . . . . .165
8 . . . . . . .170

The engine still uses oil at the same rate, but there is not a hint of blue smoke when driving nor is there any oily film in the right side pipe. Other than adding oil and plug number 2 being carbon covered, one would not have the slightest clue there was a problem. There is a bit of black smoke when starting but after a couple of minutes of warm up that ends. The engine starts every time, pulls without effort, does not miss, just runs great.

Now have about 2550 miles on the engine.

My inclination is to drive it another 500 miles and see if it has a bit more ‘breaking in’ to do. Sound reasonable???

Chuck

 

[John S]

What is the point of adding another 500 miles? You already know there is a problem with the 2nd cilinder and the answer has most likely been given by Jac Mac. It will not be solved by addind another 500 miles, though it might get worse.

John

 

[Dimi Terleckyj]

At this point I am starting to get bewildered with the attitude that it might just go away.

As we have all said,
DO NOT KEEP DRIVING THE CAR.
You will only make matters worse and cause more damage than you had in the beginning.

With mechanical motors faults do not just go away, they hide till the worst possible moment and then kick you in the butt big time.

Stripping a head is easier than pulling and rebuilding the whole motor.

Dimi

 

[John]

All of the good advice has not been ignored. I finally got around to doing the compression check today. Recall that plug #2 has been the culprit. The engine was thoroughly warmed after a good forty mile drive when we checked the compression. The results:

Cylinder Pressure
1 . . . . . . .165
2 . . . . . . .175
3 . . . . . . .170
4 . . . . . . .165
5 . . . . . . .170
6 . . . . . . .170
7 . . . . . . .165
8 . . . . . . .170

The engine still uses oil at the same rate, but there is not a hint of blue smoke when driving nor is there any oily film in the right side pipe. Other than adding oil and plug number 2 being carbon covered, one would not have the slightest clue there was a problem. There is a bit of black smoke when starting but after a couple of minutes of warm up that ends. The engine starts every time, pulls without effort, does not miss, just runs great.

Now have about 2550 miles on the engine.

My inclination is to drive it another 500 miles and see if it has a bit more ‘breaking in’ to do. Sound reasonable???

Chuck

Chuck,
I agree with the rest of the guys - certainly seems like a valve stem seal! They are generally rubber and could crack or be damaged during installation!

There may be some conditioners on the market that treat the seal if it's not seating properly around the valve stem (of course this assumes that the seal is not cracked)!

I would try this first before removing the old seal.

John

epper:

 

[DaveL485]

What is the arrangement for oil control in the cylinder? EG, I Have 2 compression rings plus one oil control ring on my pistons, I can have good compression but still have oil in cylinder problems if the scraper-type oil control ring is shot. Just looking into all possibilities.

 

[Jac Mac]

Ceslaw,
I agree with most of the comments from our fellow forum members-and would like to repeat what I already told you;
1. This sort of thing does not usually go away.
2. Any excess oil in the chamber lowers the octane value and creates carbon buildup ( Of which you are obviously aware from your plug condition ). The carbon increases the likelihood of preignition & the oil will lead to detonation. Shortly after that your current problem will become insignificant compared with the new one you might have.
3.Your Edelbrock Heads should have press on type stem seals, if you dont know how to identify whether they are still fitted correctly find someone who can.
4.If the stem seal looks OK the next likely culprit is the intake gasket or possibly a porosity problem in that runner of the intake manifold, after that you get to the oil ring on that #2 piston which could have been fitted incorrectly( ie expander overlapped or the rails not fitted correct way up or possibly one rail tweaked on fitting )

Finally in my 40 odd years of being involved with performance vehicles I have seen far to many cases where someone has gone on to do 'one more lap' to see if a problem will go away- they dont!!! And yes I have done it myself- It did'nt. Apart from that I have a decided soft spot for FE stuff and to watch from halfway around the planet while someone heads down a path that will possibly end up costing a bundle is frustrating to say the least.

Jac Mac