1992 5.7 TBI #1 Spark plug fouling

[cplnorton]

I have a 1992 5.7 with about 25,000 miles on a rebuild. The engine has about 222,000 total. It is the TBI version.

The problem I'm having is the number one cylinder fouls out the plug. Looking at the spark plug, the oil is not coming from the bottom, it is coming from the top. So I'm guessing the valve guides or the valve seals.

The engine does not smoke when it idles or if you excellerate slowly, but if you floor it, it smokes white/blue smoke. It's not terrible but enough I want to fix it.

I have the valve cover off and rocking the valves side to side there is a little wear to the guides, but what is weird is the guides on the other cylinders are worse than the one that is leaking. The number three cylinder's guide is much worse but it doesn't leak any oil at all.

Do you guys think it will help to replace the valve seal. I bought the umbrella type thinking that might help, but if it is a valve guide that will only be a temporary fix.

Is there something else I should try? Or should I just try the seals and see what happens? Thanks in advance!

Steve

[75K30]

Curious how pu can determine which direction the oil is coming from?
That is a new one to me.
There is a good chance that the valve guiide seal was damaged during the install.
I do doubt that a little play in the guide would be that big of an issue, but with so few miles, I am suprised that they have any slop at all. A fresh valve job should have taken care of that, not so long ago.
I have to assume the spring is still on, so maybe you are not seeing movement in the valve itself, and simply in the spring.
You could change the seal and see if this helps, and inspect to see why it failed.
It has been my experience that these heads have little room for error when it comes to clearance for the seals. This should use a seal that is like .560" in diameter, and these are limited to stock lift cams not to exceed .430" of lift. Too much lift or a rocker that is too tight can result in a seal that gets pinched.
You would have to machine the guide down to .530" in order to use a good aftermarket seal ("positive seal").
Just as a reminder, be very careful to ensure you have a good seal in the cylinder before you remove the valve spring. gets to be a real long day if the valve falls.

What kind od plugs are you running?
How easilly do they foul?

[cplnorton]

Hey thanks for the response. When I pull out the spark plug one side of it is dry, the other side has oild buildup. So what I did to tell the direction of the oil is put the spark plug in and take a sharpie and draw on the top of the plug. Then when I pulled it out I could which direction the oil is coming from by the marks I made with the sharpie. Please tell me if I'm wrong, because I'm a backdoor mechanic at best, but I think my idea should be feasable to tell the direction the oil is coming from. And it has to be from the top if I'm right.

As far as the plugs I'm using stock AC delcos. Whatever was made for my engine. I think they were R43TS, but I don't remember for sure. But they are standard plugs for the motor, not platinums. About every six months you need to replace the plug because it fowls out. It loses about a quart of oil an oil change.

And yes the springs are still on it. So you might be right about the play is in the spring not in the guide. I will have to get the spring off to tell.

Now I do know how to replace the seals, with the compressor and such, the one other question I have it how to adjust the valves correctly.

I'm used to working on old school big block olds engines which you just torgue the rocker down and you are done. But I know on a chevy it is different. I read in a chiltons that you actually rotate the pushrod and tighten the rocker until it gets pressure on the pushrod and then take it 3/4 of a turn more. Is this correct? Thanks guys!

[tjzz4]

These will help patch things if that`s all you are looking for.

AutoZone.com | Repair Info | Product Information - Spark Plug Non-Fouler

[75K30]

There are seeral ways to do this, and a couple is much cleaner than others, but your head is critical to obaining the proper clearance, and keeping th lift on the cam minimal to prevent this problem. Did you increase the size of the cam during the
re-build? Were the springs replaced when you re-built the engine?

As far as your troubleshooting technique, I have to say I find it interesting. I have never heard of this method and would think it is only possible for any intake valve leaks, since a leak at the exhaust valve would simply burn at the hot valve. There is some potential for this to work, and I will have to create an exeperiment to try this out.

How old is the coil in this engine? Is it the same old coil that has 200k miles on it, or has it been replaced? Perhaps you do have a seal problem, and you could have a ring problem all the same. While your symptoms seem to indicate that you have a seal problem, you may do a leak down, or compression test to make sure.

[cplnorton]

As far as the rebuild, I only know for sure the bottom end was rebuilt. I bought the truck off a friend who said he had spung a bearing so they reground the crank and put in new bearings. The cam was replaced with a stock factory one. As far as anything else goes I'm not sure.

I wonder if the heads were touched. He says he can't remember if they were or not. He had a mechanic shop do it, so I would guess not. the springs look stock and have some age on them. And the rockers are definetly original.

And I know the coil is orignal too.

I'm thinking I should try a set of seals and see if it works and if it doesn't I know it's the valve guides. I ran some lucas fuel cleaner through it and a lot of my smoking problems have cleared up. I wonder if a lot of that was old carbon built up in the engine. I might run some seafoam throught it too and see what that does.

I also wonder if I shouldn't put new valve springs in it as well, just to make sure. What do you think?

Thanks so much for responding to me and if you have anymore suggestions I'm all ears!

Steve

[75K30]

With the uncertainty of the top end, I would;
A: live with it until something big goes bad
B: consider the Band-aid anti-fouler
C: tear the heads off and inspect the codition of the stuff.
What I would not do, is install new valve springs on a set of heads that have as many miles as your does, nor would I probably go poking around too much, you may notlike what you find.
If a mechanic opened an engine up, and re-installed a set of heads with 200K miles on the clock, then I might not be too interested in opening this engine up.
If I could verify that the bottom end was good, and the heads were in need of
re-build, I might cosider having them re-built with fresh components, or buying some re-manufactured heads.
heak, for the labor involved I might just change plugs every 6 months until there is a bigger problem, and the bigger problem justifies the tear down. Until then, I would continue a little troubleshooting, and just roll with it for a while.

[chevyguy]

I understand your logic with the marking the spark plug, But i still dont think thats a difinative answer as the where its oming from. Amyhow. Might get a set or rebuilt heads from the local machine shop. Usually they are 1 for 1 turn in and they are like $150 a set or so. Not worth wasting my time rebuilding them myself.