Quickly fouled plug #4 (77 L48)
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From: Illinois, USA
Quickly fouled plug #4 (77 L48)
I've been doing some research about a problem where my #4 cylinder is fouling very quickly with oil and I am on the path that a valve seal may be to blame (at least as far as I can tell, that is the kind of seal I think is there).
No other cylinders show any serious issues (plugs looked good, but there was a light amount of oil near the plug seat)
So the questions are:
Does a plug that fouls so quickly with oil seem like a valve seal? Or is there another possible cause to be considered?
I've read a Chilton book about the process of replacing these ...and it doesn't seem to scary -- is that something I can do myself and what special tools may be needed (aside from a valve spring compressor)?
I've got a autocross race coming up in two weeks, so I'd like to have this a little better before then, as I have to drive 5.5 hours just to get there.
Thanks so much.
No other cylinders show any serious issues (plugs looked good, but there was a light amount of oil near the plug seat)
So the questions are:
Does a plug that fouls so quickly with oil seem like a valve seal? Or is there another possible cause to be considered?
I've read a Chilton book about the process of replacing these ...and it doesn't seem to scary -- is that something I can do myself and what special tools may be needed (aside from a valve spring compressor)?
I've got a autocross race coming up in two weeks, so I'd like to have this a little better before then, as I have to drive 5.5 hours just to get there.
Thanks so much.
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From: Illinois, USA
I pulled the plug and found it fouled bad. I replaced it and checked it after driving it to work and back and it's already coated (although not so bad as before where the cylinder wasn't firing due to gunk-short). While the new plug was in there, the car ran good and smooth -- definitely firing on all 8.
For this reason, I don't believe it's electrical at this point.
I agree that it's a cheap and obvious place to start ...but I believe I have done reasonable things to eliminate that (or as far as I know)
Brian.
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From: Illinois, USA
Brian.
Melting Slicks
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From: Orange Ct
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From: Illinois, USA
Me? No. Bubba? Yes. The engine was rebuilt (allegedly) about a year before I got it and I've had i going on 3 years. I say allegedly because I have receipts from the previous owner showing the work and where it was done -- but based on what I've been finding, the guy was a complete moron (mis-matched plug, motor mounts that had bolts started but never tightened, some valve springs changed -- not all) and so on. I cannot vouch for the quality of that work.
The only thing I have to work with is that the rate of fouling has gone up recently and was not this bad since the day I bought it. That is why I suspect it's a recent change. However, that doesn't mean something Bubba did couldn't have just failed on me.
Are you thinking misaligned intake gasket?
Brian.
The only thing I have to work with is that the rate of fouling has gone up recently and was not this bad since the day I bought it. That is why I suspect it's a recent change. However, that doesn't mean something Bubba did couldn't have just failed on me.
Are you thinking misaligned intake gasket?
Brian.
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From: Illinois, USA
Follow this thread to the end. May be of help
http://forums.corvetteforum.com/show....php?t=1673435
http://forums.corvetteforum.com/show....php?t=1673435
I'm going to have to get a good compression tester, so I can verify the valves and stuff are in good shape. I'll pick up some rings and see about changing the two on that cylinder and see what happens. I'll just have to read up on how to set valve lash (I've replaced some upper parts but I don't recall doing that).
I don't think I can pull intake or heads off before the race in two weeks ...can you pull a head and reinstall it without having it milled? Or does pulling it often mean milling?
Thanks for all the help so far ...sometimes it's enough to have a sanity check.
Brian.
Melting Slicks
Joined: Sep 2003
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From: Orange Ct
w1ctc ...oh, snap. This is a great post. I searched and didn't find anything, but it seems like it just got started. Lots of good information and it does seem to have many parallels to my situation, except the engine type and year -- which may change the detail parts but not the overall function.
I'm going to have to get a good compression tester, so I can verify the valves and stuff are in good shape. I'll pick up some rings and see about changing the two on that cylinder and see what happens. I'll just have to read up on how to set valve lash (I've replaced some upper parts but I don't recall doing that).
I don't think I can pull intake or heads off before the race in two weeks ...can you pull a head and reinstall it without having it milled? Or does pulling it often mean milling?
Thanks for all the help so far ...sometimes it's enough to have a sanity check.
Brian.
I'm going to have to get a good compression tester, so I can verify the valves and stuff are in good shape. I'll pick up some rings and see about changing the two on that cylinder and see what happens. I'll just have to read up on how to set valve lash (I've replaced some upper parts but I don't recall doing that).
I don't think I can pull intake or heads off before the race in two weeks ...can you pull a head and reinstall it without having it milled? Or does pulling it often mean milling?
Thanks for all the help so far ...sometimes it's enough to have a sanity check.
Brian.
If you go all the way to the end (page 5) he found a bad "o" ring.
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From: Illinois, USA
Yeah, the pics were very telling in his case and I was suspecting that in mine, but was nothing more than a hunch. My plan is to get some new o-rings and install them on both valves in that cylinder. If nothing else, I can see what affect that has on the symptom -- but the money is on that is the likely cause. Sorry if my response suggested I hadn't read the full article and understood the o-ring (or valve seal -- it seems to have many affectionate names) was the likely source of his leak.
I'm sure I would have missed it if you hadn't pointed it out, so I'm quite grateful for your assistance (more so if it happens to be the problem)
Cheers!
Brian.
I'm sure I would have missed it if you hadn't pointed it out, so I'm quite grateful for your assistance (more so if it happens to be the problem)
Cheers!
Brian.
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From: Illinois, USA
Update
Thanks everyone for the great help with this ...I've made some progress and I figure I'd post the update and perhaps toss out one more question.
1. I replaced both of the valve stem seals on #4 intake and exhaust cylinders and re-lashed. The old seals were brittle/hard and broke and pushed out of the channel they should be in (not entirely ...but definitely crap). Of course, being this brittle makes me worry that the rest are just as bad (thanks bubba).
2. When I hooked up the air compressor, I noticed air coming out of the EGR port (I had it removed), and this didn't seem normal to me. I get the impression it should have held air without leaking it back through the egr side. So I opened the exhaust value while the cylinder was under pressure and I got a pop of air. Nothing like when I did it with the intake. Something to be concerned with? Valves all gunked up? Time for some Seafoam?
I guess I wish I had a way to find out what else was lurking. I fired it up and it ran after the work, so it couldn't be too bad (like when I code -- did it compile? Then it works. Was data returned? Then it was right)
Thanks,
Brian.
1. I replaced both of the valve stem seals on #4 intake and exhaust cylinders and re-lashed. The old seals were brittle/hard and broke and pushed out of the channel they should be in (not entirely ...but definitely crap). Of course, being this brittle makes me worry that the rest are just as bad (thanks bubba).
2. When I hooked up the air compressor, I noticed air coming out of the EGR port (I had it removed), and this didn't seem normal to me. I get the impression it should have held air without leaking it back through the egr side. So I opened the exhaust value while the cylinder was under pressure and I got a pop of air. Nothing like when I did it with the intake. Something to be concerned with? Valves all gunked up? Time for some Seafoam?
I guess I wish I had a way to find out what else was lurking. I fired it up and it ran after the work, so it couldn't be too bad (like when I code -- did it compile? Then it works. Was data returned? Then it was right)
Thanks,
Brian.
Le Mans Master
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From: Butler Pa
Did you do a compression test? Sounds like a burnt exhaust valve.
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I didn't have time to do it last night, but I already bought a good tester with expectations of doing that soon. I guess that will be tonight
Burnt valve ...crap. That can only mean one thing: the heads are coming off which pretty much means a redo. Ugh.
Brian
Burnt valve ...crap. That can only mean one thing: the heads are coming off which pretty much means a redo. Ugh.
Brian
Le Mans Master
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Burnt valve is possible. More likely a chunk of carbon on the seat. Do the compression test- Disconnect the ignition, block the throttle wide open, pull ALL the spark plugs and start checking. Low to high should be within 10% give or take a bit. Look at the first stroke on the compression tester and then one a little later. I usually give them 5 or 6 and see where they are. Record the numbers and let's see what you've got..
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Joined: Apr 2005
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From: Illinois, USA
Burnt valve is possible. More likely a chunk of carbon on the seat. Do the compression test- Disconnect the ignition, block the throttle wide open, pull ALL the spark plugs and start checking. Low to high should be within 10% give or take a bit. Look at the first stroke on the compression tester and then one a little later. I usually give them 5 or 6 and see where they are. Record the numbers and let's see what you've got..
Brian.
Instructor
Joined: Nov 2003
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From: Clifton NJ
"Tune-up in a can" sounds like a beer to me!!
I've used the old time msited water into carb an elevated RPM to clear out suspected carbon deposits. The engines I did that to ran smoother afterward, and while I didin't tear the engines down to get pictures, I surmised the water did the trick. Perhaps Seafoam or other such products would accomplish the same effect, don't know.
BB NJ Ken
I've used the old time msited water into carb
an elevated RPM to clear out suspected carbon deposits. The engines I did that to ran smoother afterward, and while I didin't tear the engines down to get pictures, I surmised the water did the trick. Perhaps Seafoam or other such products would accomplish the same effect, don't know. BB NJ Ken
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Well, crap. Sounded like a great plan until I tried to execute it -- and now I have a new symptom. No start. 
I ran the car briefly last night after putting the valves back in, and it ran fine. Today, I have lights and power, but when I crank, the lights only dim slightly (so there is some current draw when key is moved to start, but the lights don't go out totally like the hi-current windings were being engaged). There is no click or any other noise. To rule out the battery being too low, i have it on a 6A charger to see if that makes any difference, but things seem too "bright" and don't dim enough for me to be convinced that is it.
So, since it's hard to test the system as I can't turn the key and be under it at the same time, anyone know what might be a good place to start? Otherwise, I would suspect a stuck bendix.
Where would you look?
Brian.
I ran the car briefly last night after putting the valves back in, and it ran fine. Today, I have lights and power, but when I crank, the lights only dim slightly (so there is some current draw when key is moved to start, but the lights don't go out totally like the hi-current windings were being engaged). There is no click or any other noise. To rule out the battery being too low, i have it on a 6A charger to see if that makes any difference, but things seem too "bright" and don't dim enough for me to be convinced that is it.
So, since it's hard to test the system as I can't turn the key and be under it at the same time, anyone know what might be a good place to start? Otherwise, I would suspect a stuck bendix.
Where would you look?
Brian.