L79vette66

What does the transmission have to do with this post? Does the Classic Chevy 5 speed make your engine plugs run better.

Joys

I second this idea, brake fluid would do this to your plug. I also would recheck that all wires goes to the correct cylinders..

NEVERL8

No power brakes.

NEVERL8

I believe you are correct given the symptoms of the car. At this point I am prepared to pull the right side head and take a look. Tonight after work I will start the process.

Really wish I had not put all the AC hardware and underbody exhaust back on the car. I now have to take a lot of that hardware off and this will be a major PIA.

Thanks for everyone's input. I will update and post pics once the head is off. Stay tuned.....

MikeM

Transmissions that have a vacuum modulator draw their vacuum from the fitting in the intake manifold, just above the #8 intake runner. Sometimes, when the modulator fails, the engine will suck transmission fluid up the vacuum line and into the engine.

GMJim

Thanks MikeM

L79vette66
I have replaced hundreds of these valves over the years for this reason.

To answer your question about our transmissions, yes! our transmissions will work wonders for your plugs.

NEVERL8
On a more serious note based on the info I have to agree with the others and suggest that oil is likely getting in under the intake and fouling the plug.

INMYBLOOD

If the cam is going down you may hear a "huff" but it may be hard to hear if it's running very ruff. My brothers 402 wiped the cam slowly and it always seemed to "huff" in the exhaust

67-427ci

Bruce: If it turns out you need valve seals, there is no need to pull the head unless you want to clean the combustion chamber and piston of burnt-on carbon. You can easily replace the seals from the top side (with the head on the engine). Once again, good luck tracking down the problem.
Roy

67vetteal

I imagine you have pulled the Head by now. Visual inspection by an experienced mechanic will be a major help. If not possible do your best. Check the piston tops for a numeric reading to see if you have over size pistons. How about posting ALL your block numbers, casting etc. It would be nice to know what you have. Check your cylinder walls for abnormality's. Did you check your Wires with an Ohm gauge? Install that new Cap/Rotor? Take the Head, (#8), to a machine shop and have the Valves pulled and checked on the bad cylinder. Al W.

NEVERL8

I cannot discount the bent electrode on the #8 plug when I first got the car. Something about this says it is not a coincidence that the #8 plug shows bad oiling and the electrode on the plug was bent over. On the other side, though, both of the plugs I put in since then did not have a bent electrode when removed. Still, I have learned over time to never discount a clue. The bent electrode bothers me.

I did not know the valve guide seal was replaceable without removing the valve (meaning pulling the head). But, if the valve guide is worn or scored replacing the seal will only be a temporay fix. Am I thinking correct about this?

I need to contact the person who rebuilt the engine to see if I can get other information that will lead me to the correct diagnosis. I will try contacting him tonight.

NEVERL8

I will get the block, head and intake casting numbers tonight, and post them. I believe everthing is correct for the L79 engine, but I will verify.

Don SSDD

"I did not know the valve guide seal was replaceable without removing the valve (meaning pulling the head). But, if the valve guide is worn or scored replacing the seal will only be a temporay fix. Am I thinking correct about this?"

You have to keep the valve from dropping down on top of the piston. This can be done with compressed air through the plug hole. Somebody else will likely give you more specifics on this, but worth doing this first before removing the intake and head.

On the other hand, if that was screwed up on #8, you may want to remove both heads and check all the valves and seals. Then you know what you have.

Don

NEVERL8

I am familiar with pressurizing cylinders to prevent valves from dropping into the cylinder. I replaced all the valve springs on my 95 LT1 this way.

I will pull the valve cover off tonight and take a look at #8. I really have little to loose by removing the springs and looking at the valve stems, guides, etc.

magicv8

I have bent a lot of electrodes installing spark plugs in cars like our c2s that are hard to start the plugs into the head threads. When they fall to the floor, you have to look carefully to make sure the plug was not damaged in the fall. IMO it's probably that simple.

NEVERL8

The thought has crossed my mind. I have bent spark plug electrodes before when installing plugs on my 70 LT1. It had headers and one of the plugs was very hard to get to. I bent the electrode by trying to push it into the hole where I could not see it.

This car, though, has another story. The engine was rebuilt just before I bought it. The spark plugs were inserted into the engine while it was still on the engine stand, before it was installed into the car. The exhaust manifolds were on the engine as well (I have pictures of the engine just before it was dropped into the car) I need to speak with the engine builder (maybe tonight) but I find it unlikely that one would injure a spark plug under these circumstances. The gentleman who built the engine was methodical and detailed from all evidence I see.

You may be correct but I smell a fish.

An interesting question I just thought of is: What if the electrode WAS bent before insertion into the #8 cylinder. Would a non functioning sparkplug cause some type of oil related failure after driving the car for a couple hundred miles????? Would this somehow injure the valve guide seals, gaskets, rings, etc. causing the problems I see today?

Bruce

MikeM

.

An interesting question I just thought of is: What if the electrode WAS bent before insertion into the #8 cylinder. Would a non functioning sparkplug cause some type of oil related failure after driving the car for a couple hundred miles????? Would this somehow injure the valve guide seals, gaskets, rings, etc. causing the problems I see today?

Bruce[/QUOTE]

I don't see how it could cause any lasting serious damage.

The fact that it had CARBON on it tells you that it had been firing at one time BEFORE the tip was mashed shut. I think a piece of carbon came loose and got hung between the piston and the plug.

It looks like your replacement plugs have been firing too. The mystery to me is why you see NO smoke. Your miss or vibration may be a combination of a lean mixture and the fouled plug. When you pill the intake, pay close attention to the gasket seal surfaces and the interior of the intake runners, looking obviously for oil tracking or cracks. If you see carbon buildup on the backside of your intake valve when you pull the intake, you can just about bet the oil is coming in that cylinder from the top end somewhere, not through the rings.

I can't remember if any of the rocker studs are above the intake ports. If they are, that could be another path for oil to pull through.

67-427ci

Bruce: This is what the back of the valve will look like if you have oil getting in from the top side. You will be able to see it as soon as you pull the manifold. Good Luck.
Roy

NEVERL8

Thanks. I was going to start the tear down process tonight but did not. I wanted to do one last check. I installed a new plug, have run the car for 15 minutes under various load and am now waiting for it to cool down. Once cooled down I will pull the plug for a visual, take a couple of pics and post them, and fire up the engine with the plug removed to make sure it is firing. Too tired tonight to work on the car. I would make stupid mistakes and really kick myself for it.

When I get into the tear down I will take copious notes and pics. I'll keep the forum updated as I go. I am sure many people will benefit from my effort to uncover the the root cause of the problem.

The response from everyone out there has been great.

Later
Bruce

67vetteal

One last thought, seeing as you haven't torn down the motor. There is a spark plug oil fix adapter. Your plug screws into the adapter and then the whole setup gets screwed into the plug socket. These were used years back to keep your plugs out of the combustion chamber in a motor that had bad rings as many cars did years back. It would be of interest to see how long the plug continued to fire compared to now.
Your problem is beginning to point to a faulty valve guide or manifold gasket. Don't overlook the Modulator as someone earlier pointed out. Al W.

Procrastination Racing

Looking at this plug, there is a tremendous amount of oil that has
flowed over it to be this heavily fouled and encrusted in 200 miles.

The rear of the cone shows it is firing, or the entire insulator cone
would be black like the front, not gray like the back.

You have a serious oil flow and it is oil, as you can see the oil on the
plug.anything else would encrust the plug, but not leave the liquid
black oil there.

1. Valve guide shot, along with oil seal gone, off the seat, etc.
2. Rings stuck in groove, pumping oil into the cylinder.
3. Intake gasket way off, letting oil suck in the intake port.
4. Intake/head surfaces not parallel, leaving a gap at the bottom
the gasket won't seal.
5. Valley breather canister (oil separator) missing or defective and
letting oil suck out of valley through vent tube into intake.
6. Cracked head.
7. Cracked intake runner.
8. PCV valve stuck open or missing.

No smoke is confusing, unless the oil is so heavy that it is literally
flooding the cylinder and not burning. Check the exhaust pipe to
see if it is oily. I lost two cylinders in a suburban once, towing from
FL to Chicago, and ran from about Atlanta to Chicago with oil blowing
out everywhere. When I got to Chicago, I had one cylinder with
grooves wider than screwdriver blades and about as deep. No smoke
out the exhaust, but a couple of quarts every gas stop.

If the heads were milled, your intake could be not seating correctly.
Take a set of intake gaskets, paint them both sides, and slap them
and the intake on the heads to see where they mate.

If the compression tests show ok, then the rings are probably not the problem.