spark plugs.... Over thinking!

SquareRoot

Full Access Member
Joined
Mar 18, 2017
Posts
2,092
Reaction score
2,816
Location
Arizona
First Name
Mike
Truck Year
85
Truck Model
K20
Engine Size
350
15w40 it s diesel oil? Hmmm.... everyone on my Duramax forum wants to defy GM and run that viscosity. It's the anti ash ingredients that make diesel oil engine specific. But to my point; intake manifolds are notorious for bad fuel distribution, especially GM on the corner cylinders. My number 8 is always darker than the others. Another point is that modern fuels with ethanol and all the other stuff make reading plugs almost useless. The EFI tells me what's the AFR is and it has no correlation to the color of the plugs.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
15w40 it s diesel oil? Hmmm.... everyone on my Duramax forum wants to defy GM and run that viscosity. It's the anti ash ingredients that make diesel oil engine specific. But to my point; intake manifolds are notorious for bad fuel distribution, especially GM on the corner cylinders. My number 8 is always darker than the others. Another point is that modern fuels with ethanol and all the other stuff make reading plugs almost useless. The EFI tells me what's the AFR is and it has no correlation to the color of the plugs.
I've run diesel oil 15W40 in gas vehicles in the past, and am currently running it in my Jeep. I've never had a problem. The main attractions are, my tractor needs it, I've got it around and well it's cheap. My truck has always given a puff of blue on start up but doesn't use much oil at all. I've never really kept track when I add a quart, but it's just a few times between oil changes so I'd have to guess I add a quart every 800 - 1,000 miles.

I know what you mean about reading spark plugs, and I completely agree with your comments fuel making it much harder to read plugs, but I think I may have posted pictures earlier in the thread. #7 plug is loading up with oil deposits till it fouls. Now wondering if combining not so great valve seals, with those anti ash ingredients is my problem.

Well one things for sure it'll be interesting to see. In a few days of driving I should be able to tell if the deposits are forming on that plug. It won't foul out in a couple days, but I'll be able see deposits by then.
 

SquareRoot

Full Access Member
Joined
Mar 18, 2017
Posts
2,092
Reaction score
2,816
Location
Arizona
First Name
Mike
Truck Year
85
Truck Model
K20
Engine Size
350
I also once had a similar issue that was caused by a leaking intake manifold gasket. Swapped to the Fel-Pro O-ring style and fixed that issue.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
I also once had a similar issue that was caused by a leaking intake manifold gasket. Swapped to the Fel-Pro O-ring style and fixed that issue.
I don't "think" it's the intake, but it could be, and I need to remove it to get the EGR ports opened up, so the gasket would get replaced at that point anyway.

Well she ran good this morning. Nothing more than that to report so far.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
I don't "think" it's the intake, but it could be, and I need to remove it to get the EGR ports opened up, so the gasket would get replaced at that point anyway.

Well she ran good this morning. Nothing more than that to report so far.
That day, I pulled the plugs at lunch to find #7 about 1/2 way to being fouled. That evening it would idle crappy and has continued to do so especially after working it, I'll get to that in moment.

I'm going to recap for anyone that hasn't read the entire thread, I had been running ACDelco CR43TS plugs, the truck calls for R45TS or CR43TS. The PO had the CR43TS's in it when I bought it so I just carried on with those. As long as I've owned the truck, it's liked to give a puff of blue at start up, so given the engine we are talking about I assumed valve guides. I'd never had a plug foul out before the start of this thread on Feb. 26th. I fouled #7, the plugs had about 8K on them. I replaced the set with NGK UR4's which are about equivalent to R44TS or R45TS, so at least a touch hotter. I did that because it's what I could get in a hurry, I ordered a set CR43TS and went back to those a week later. The following week, I'd foul #7 again, so I put one of the slightly hotter NGK plugs in that hole, which has been a somewhat better but I've changed it a few times more. Lately I've also noticed if I'm towing my trailer, or run it hard up a long hill, it'll miss like one cylinder is not contributing for about 30 seconds to a minute after if I pull up to a stop. Last weekend I did cap, rotor, wires, and module. No change with the idle miss after hard run.

It was suggested to me that it might be a valve with an issue, a weak or compressed (from time) spring or seat that is worsened by heat, but quickly gets back to sealing well enough after head temps come down a bit. And that would also be why I'm not seeing it on a compression test.

Another thing in the back of my head is that not to long before that first foul out I'd switched to running diesel oil in the truck. Prior to that my program had been conventional 10W40 with a 1/2 bottle of hyperlube, because I felt it helped a little with puff of blue at start up and when I'm towing the extra stickiness couldn't hurt in a high mile motor.

Now I'm not saying this is going to work, but it looks promising at the moment. I've had some concern about anti-ash additives in the diesel oil. The thing is I'm just not using much oil, maybe a quart every 800 - 1,000 miles. I've certainly had motors that burned a lot more that didn't foul plugs. So before I left work today I did what will be my last effort before deciding the valve train is to worn out to continue as is. So I dumped the diesel oil, changed filter and filled it with 10W40 and a full quart of hyperlube. I did a through decarb and replaced the plugs with a full set of NGK UR4's. Double checked no excessive slop in timing chain, ignition timing set properly ect. Well on the drive home I ran it as hard as I safely could on each hill and then came to a stop as soon as I could at the top. It did not give me the rough idle thing and actually ran better than it has since before the first foul out. Tomorrow will be the real test, after work I'll have to do a 2 mile long hill loaded, I'll run it floored no doubt and it will act up after that if it's going to. At some point tomorrow at work I'll pull #7 just to see what's happening there so far.

Assuming tomorrow goes ok, it'll just be wait and watch for the next several weeks to see what happens. I'll read the plugs after a while to see if they look to hot for any of the cylinders. If all goes well then at the next oil change I'd go back to just a 1/2 quart of hyperlube, but with the warmer weather coming I'm less concerned about cold flow. How the plugs read will determine if I leave the slightly hotter plugs in or step it back down. Even if it does turn out that the diesel oil was pushing the fouling over the edge I think this is a wake up call that this engine is nearing the end. If I can get through to next winter when the farm slows down again I'll order an engine ahead of time and put it in when I don't need the truck as much.

@Bextreme04 Since I told you I'd tag you so you could get a little more of the story.
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
Morning update. #7 has a mostly black insulator which looks like it's from oil, which isn't really a surprise, but there is no build up and it's dry. Last time I pulled #7 it was wet with oil. Obviously I'd like it if it looked normal but I knew that wouldn't happen. So we will see what happens when I pull that 2 mile hill loaded tonight. If it acts up after that I'm not going to be able to put off replacing the engine, if it doesn't act up then I'll feel more comfortable trying to keep it going for a while. I'd be willing to change the plug out every now and then until I can replace the engine, provided that it runs good between changes. We shall see, test tonight and will report back, but it'll likely be late in the evening.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
Ok here's the last update for the day. But first I want to make a comment about this. Not only is fun to share with folks here, but also it gives me a place to go back and re-read for myself what happened when as I can never remember all the details.

So this afternoon I had to make a part run for the shop. About 30 miles to the south, so 60 round trip mostly freeway, not exactly flat but no real hill climbs either, regardless it's more mileage logged since the oil swap and tune. That went just fine and I expected that. Tonight after work. First stop car wash, this is a touchless car wash where you drive in and doors close in front and behind. I do not recall smelling the trucks exhaust during a wash in the past and I've been to this wash a few times, but on this occasion I could smell it near the end of the wash, fairly strong. Truck has a cat converter that is pretty new so it's in good health. My question on this, I'm now running slightly hotter plugs across the board, anyone think hotter plugs would effect exhaust smell? My thought is given that it effects the burn it might. Also we know I have oil control issues on #7 and I have a healthy catalytic converter, so the cat maybe cleaning it up enough to make it colorless and simply smell strong rather than oily. Also the car wash does an under carriage wash and it may have cooled the cat enough to make it not fully doing it's job, well that thought makes me feel a little better. I guess I'll just monitor that, but also I'd be interested in others opinions.

From there I got my load drove on the highway for a few miles and did that 2 mile hill. I have to admit I was intentionally hard on it. Did the entire two miles with my foot all the way to the floor. I kept it there as I crested the hill, by the time I felt I was going to fast I looked at the speedo to see the needle past 85, oops, not what I intended but definitely a good hard run up the hill. And sure enough around the corner the light is red. As I pulled up to it I was almost expecting it to run rough. Nope, pretty darn good, not perfect no, but also it's a high mileage 305, certainly a huge improvement and acceptable.

So we'll see what happens as the miles add up, I kick myself for the doing the diesel oil thing, as I feel like I brought this all on myself, but also glad that it seems I'll be able to run this engine for a while longer.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
Ok, I need to catch everyone up here on what's been going on with my plugs. #7 is still fouling and quite quickly. It is marginally better than when I was running the diesel oil, but not much really. So that is debunked.

I did valve stem seals on #7 only last Thursday and it has made no noticeable change. I ran a compression test on #7 and got 170, which is what I got on my last comp test.

If ya'll would examine this picture. This is from last month, but when I pulled the plugs on Thursday (I pulled all on the driver side bank they looked pretty similar.

You must be registered for see images attach


Take a look at 1, 2, 4, 6 & 8. Those all look pretty good. #5 looks acceptable. #7 is fouled out. At the time I thought nothing of #5, it's a little dark but acceptable. If as @Rusty Nail has hypothesized, and I have a blown intake gasket between 5 & 7 sucking oil in could #5 be evidence of that? @SquareRoot you mentioned that you had an intake suck oil, so curious about your thoughts on this. And of course anyone else that has a thought here please comment.

Side bar I need a water pump too now....
 

SquareRoot

Full Access Member
Joined
Mar 18, 2017
Posts
2,092
Reaction score
2,816
Location
Arizona
First Name
Mike
Truck Year
85
Truck Model
K20
Engine Size
350
Ok, I need to catch everyone up here on what's been going on with my plugs. #7 is still fouling and quite quickly. It is marginally better than when I was running the diesel oil, but not much really. So that is debunked.

I did valve stem seals on #7 only last Thursday and it has made no noticeable change. I ran a compression test on #7 and got 170, which is what I got on my last comp test.

If ya'll would examine this picture. This is from last month, but when I pulled the plugs on Thursday (I pulled all on the driver side bank they looked pretty similar.

You must be registered for see images attach


Take a look at 1, 2, 4, 6 & 8. Those all look pretty good. #5 looks acceptable. #7 is fouled out. At the time I thought nothing of #5, it's a little dark but acceptable. If as @Rusty Nail has hypothesized, and I have a blown intake gasket between 5 & 7 sucking oil in could #5 be evidence of that? @SquareRoot you mentioned that you had an intake suck oil, so curious about your thoughts on this. And of course anyone else that has a thought here please comment.

Side bar I need a water pump too now....
Yep. That's pretty much the same thing I was experiencing. I had used the Edelbrock gaskets that came with my EFI swap. They delaminated and shifted causing #8 & 2 plugs to foul quickly....just like your picture. Replaced gaskets with fel-pro O-ring style and been good ever since.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
@SquareRoot Mike, thanks for the info. and reinforcement.

@Rusty Nail Ok fine. I have 4 days off working coming up next weekend and not planning to go anywhere. I'll make plans to pull the intake.

I'm not fully convinced this is the problem, but like with the stem seals I'm feeling like it's worth a shot. And wouldn't I feel stupid if I found a ruptured intake gasket while pulling it off to put it on a rebuilt 350.
 

Rusty Nail

Victim of Culture
Joined
Jan 29, 2015
Posts
8,513
Reaction score
7,187
Location
Your mom's house
First Name
Rusty
Truck Year
1977,1988
Truck Model
C20, K5
Engine Size
350, 350
I also condone reducing the gap in #7 to 0.35, she said it first @AuroraGirl
I believe a smaller gap creates a more intense spark which may help to burn the oil.
:waytogo: Me n Snoots tryna help ya :waytogo:

Tbh Robyn I think the whole mess is well past ridiculous.

Seems obvious to me Mr.overthinker... Puff of smoke on start up is a valve guide sure but it requires a lot of engine vacuum to pull the oil out of the ring in the next cylinder? Whatever.

You are overlooking the obvious.

Then after reading...where to start with so much wrong?
Duh.
The check engine light...come on man..

Any tech does it. Start with the most obvious. There are half a dozen errors present AND NO PIX.

ok.
You need a new distributor. OBVIOUSLY.
They are cheap - your time is not.
Go ahead a toss a new one in , the clock is ticking. Buy loaded with the coil and everything...

Umm. PCV is blocked off? No.
Full stop.

You'll need to fix that because it is destroying your AF ratio/mixture...the carburetor is built to burn it and frankly Robin, you are screwing. around.

EGR?
Come on dude, how the heck do you expect it to run right knowing the intake has clogged passages? Why am I here?

Just like the PCV - a Quadrajet is built for that, you cant tune it out so simply - there are passages in the carb that need it AND the EGR fumes.

Are you
Playing?
Having fun?
Experimenting?

What's the deal dude?

Start from the beginning . :rolleyes:

The oil control ring may be flipped..that really happens.
MMO is your friend and that's how you fix it without taking it apart if it's your trouble.

Look on the bottle dangit...
Unleash engine power yo!

You must be registered for see images attach



We'll send a bill, try to focus.
You've lost control - sounds like that engine bay is running YOU and that ain't the way to do it.

You need to have a talk with the truck I guess - play her this Prince song and she'll get nervous. :D


*p.s. All I run is Delco R45TS and I'm @1500 feet.

xc_hide_links_from_guests_guests_error_hide_media


Did you even TRY to tighten the intake bolts?
I bet you didn't.
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
3,368
Reaction score
3,556
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
350
I also condone reducing the gap in #7 to 0.35, she said it first @AuroraGirl
I believe a smaller gap creates a more intense spark which may help to burn the oil.
:waytogo: Me n Shoots tryna tell ya :waytogo:

Tbh Robyn I think the whole mess is well past ridiculous.

Seems obvious to me Mr.overthinker... Puff of smoke on start up is a valve guide sure but it requires a lot of engine vacuum to pull the oil out of the ring in the next cylinder? Whatever.

You are overlooking the obvious.

Then after reading...where to start with so much wrong?
Duh.
The check engine light...come on man..

Any tech does it. Start with the most obvious. There are half a dozen errors present AND NO PIX.

ok.
You need a new distributor. OBVIOUSLY.
They are cheap - your time is not.
Go ahead a toss a new one in , the clock is ticking. Buy loaded with the coil and everything...

Umm. PCV is blocked off? No.
Full stop.

You'll need to fix that because it is destroying your AF ratio/mixture...the carburetor is built to burn it and frankly Robin, you are screwing. around.

EGR?
Come on dude, how the heck do you expect it to run right knowing the intake has clogged passages? Why am I here?

Just like the PCV - a Quadrajet is built for that, you cant tune it out so simply - there are passages in the carb that need it AND the EGR fumes.

Are you
Playing?
Having fun?
Experimenting?

What's the deal dude?

Start from the beginning . :rolleyes:

The oil control ring may be flipped..that really happens.
MMO is your friend and that's how you fix it without taking it apart if it's your trouble.

Look on the bottle dangit...
Unleash engine power yo!

You must be registered for see images attach



We'll send a bill, try to focus.
You've lost control - sounds like that engine bay is running YOU and that ain't the way to do it.

You need to have a talk with the truck I guess - play her this Prince song and she'll get nervous. :D


*p.s. All I run is Delco R45TS and I'm @1500 feet.

xc_hide_links_from_guests_guests_error_hide_media


Did you even TRY to tighten the intake bolts?
I bet you didn't.
Ya, Ya, Ya thanks for the lecture, but you do have some points. My only defense is that it is easy to become complacent when you know there are issues, but the truck is running ok and your busy.

Once again, for the record I've never run the truck on the road without a working pcv valve. It was only disconnected briefly during testing I described that test to you in the valve stem thread I think.

I'm running .035 on #7, but may have never mentioned that.

Ok enough I'll order the gaskets on Monday at work. I'll take some damn pictures. Anything else you'd like. Maybe a beer? :drink_nl:


Ok wait I'll recycle some pics for you. First two are various times I've pulled #7 and what I found. Last pic is just engine compartment.

You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
7,800
Reaction score
4,432
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
I think a smaller gap is technically not more intense but its a longer duration. if its possibly a harder cylinder to fire, say its fouled or oil is in there, the stress maybe means the .035 could be stronger because its within the systems capability? Idk just shooting random thoughts lol
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
3,091
Reaction score
3,066
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
I think a smaller gap is technically not more intense but its a longer duration. if its possibly a harder cylinder to fire, say its fouled or oil is in there, the stress maybe means the .035 could be stronger because its within the systems capability? Idk just shooting random thoughts lol
Yes and No... a larger gap will require a higher voltage to jump the gap. It is a hotter, more intense, spark. The duration can be longer(sometimes) with a smaller gap, because the coil doesn't have to charge as much in order to create enough voltage to jump the gap. That's why modern CNP setups have large gaps ~0.065", they get the hot spark and don't have to worry about duration because each cylinder has its own coil.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
7,800
Reaction score
4,432
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Yes and No... a larger gap will require a higher voltage to jump the gap. It is a hotter, more intense, spark. The duration can be longer(sometimes) with a smaller gap, because the coil doesn't have to charge as much in order to create enough voltage to jump the gap. That's why modern CNP setups have large gaps ~0.065", they get the hot spark and don't have to worry about duration because each cylinder has its own coil.
yes, I should have clarified, a cylinder with more pressure, more stuff like oil or carbon etc...(such as on the plug itself) will require more to fire. so shortening the gap maybe then eases the needs on the coil and thus allows a spark to happen that may have been weaker all things equal otherwise with more gap?

im trying to word it as clearly as I can lol but I know when reading about waste spark, the cylinder not needing sparkas its on the exhaust stroke doesnt require as much voltage, but I also just learned apparently its also reversed polarity and im not sure now if that somehow affects it lol
 

Latest posts

Forum statistics

Threads
36,195
Posts
764,798
Members
25,352
Latest member
El82Blazer
Top