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Old 04-29-2013, 01:40 PM
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Read my plugs

Check out my pic of the spark plugs from my sbc400 from last year. I pulled them and replaced yesterday, all of them have about 500 miles on them, but quite a bit of idling time on them. The pic shows them as if looking at the front of the motor, #1 being on the bottom right. Nevermind the oil under #3.

From what I know and have read about plugs, they're all pretty much showing richness as they're "smokey" and dark. But what's going on with #3 and #7? Both are lighter and actually looks better than the rest. Is that correct? And then what would make those have such a change compared to the others? Car does have solid lifters, which I'm thinking may come into play here (bad adjustment?), but not sure.

Thoughts, ideas?
Thanks
/D
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Old 04-29-2013, 02:55 PM
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Quote:
Originally Posted by david-b View Post
Check out my pic of the spark plugs from my sbc400 from last year. I pulled them and replaced yesterday, all of them have about 500 miles on them, but quite a bit of idling time on them. The pic shows them as if looking at the front of the motor, #1 being on the bottom right. Nevermind the oil under #3.

From what I know and have read about plugs, they're all pretty much showing richness as they're "smokey" and dark. But what's going on with #3 and #7? Both are lighter and actually looks better than the rest. Is that correct? And then what would make those have such a change compared to the others? Car does have solid lifters, which I'm thinking may come into play here (bad adjustment?), but not sure.

Thoughts, ideas?
Thanks
/D
They are fuel fouled as you suggest except for 3 and 7. I'm not sure how Accel arrives at heat ranges nor how consistent that is plug to plug. Fuel fouling can be the result of the plug not getting hot enough to burn off contamination as well as it can be excessive fuel. This can also be a problem of engine operating temperature, which while happens with iron heads, can be a real problem with aluminum because Al pulls heat away faster so a plug that's marginally too cold in an iron head is really too cold in an aluminum head.

I'd try a different brand plug Autolight and NKG seem to fit around headers best before going deep into the fuel system. If you're using aluminum heads I'd not use less than a 190, preferably a 200 degree thermostat to keep more heat in the combustion chamber.

Bogie
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Old 04-29-2013, 03:51 PM
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Looks like a tighter gap on #3, or is that my eyesight?
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Old 04-29-2013, 08:41 PM
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After instituting Old Bogie's fix, if the plugs are still fuel-fouled, then the float level in the carb is set too high or the fuel pump is over-powering the needle and seat and blowing raw fuel into the intake manifold, creating an over-rich condition. Holleys can tolerate about 6 psi before the needle yields, Edelbrocks, Carters and Rochesters about 5 psi.

I have seen this "too much fuel pump" scenario many times.
Tee off at the carb inlet and run a small copper line back to the firewall, up past the hood lip and onto the grillework in front of the windshield. Mount a mechanical, liquid-filled 0-15 psi fuel pressure gauge on the grillework so that you can read the gauge through the windshield while you drive. You don't need a fancy mount, because the gauge will only be there long enough to determine if you have a problem or not, so mount it with duct tape, tie wraps, whatever.

If you're using a mechanical, cam-driven fuel pump, then replace the pump with a standard, run of the mill Carter pump for the year and model of your vehicle. If using an electrical fuel pump, splice in a fuel pressure regulator between the carb inlet and the pump.
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Old 04-29-2013, 09:11 PM
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Thanks for the responses guys.
Heads are aluminum. I didn't measure the plugs after pulling them. Always measure prior to installation and they were all good then.
Thermostat is I believe a 180, electric fans turn on at about 210. Usually see temps of average about 190 while driving.

Took the car out this evening and she ran great. Smooth idle and great acceleration. I did a couple quick WOT off the line and she stutters off the line and bogs a little, but as soon as it gets past that she flies. And then afterward she stutters some more, and almost dies, but then back to normal. Is that a richness issue? Would this and the burnt plugs be a carb issue or a timing issue?

Also has a rough time starting from when cold. Like the first start of the day, will fire up but then stutter and die without giving gas.

Thanks
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Old 04-29-2013, 09:14 PM
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Originally Posted by techinspector1 View Post
After instituting Old Bogie's fix, if the plugs are still fuel-fouled, then the float level in the carb is set too high or the fuel pump is over-powering the needle and seat and blowing raw fuel into the intake manifold, creating an over-rich condition. Holleys can tolerate about 6 psi before the needle yields, Edelbrocks, Carters and Rochesters about 5 psi.

I have seen this "too much fuel pump" scenario many times.
Tee off at the carb inlet and run a small copper line back to the firewall, up past the hood lip and onto the grillework in front of the windshield. Mount a mechanical, liquid-filled 0-15 psi fuel pressure gauge on the grillework so that you can read the gauge through the windshield while you drive. You don't need a fancy mount, because the gauge will only be there long enough to determine if you have a problem or not, so mount it with duct tape, tie wraps, whatever.

If you're using a mechanical, cam-driven fuel pump, then replace the pump with a standard, run of the mill Carter pump for the year and model of your vehicle. If using an electrical fuel pump, splice in a fuel pressure regulator between the carb inlet and the pump.
Posted the same time I did! Have an Edlebrock on there now. Fuel pump is cam driven, believe a Holley. I will get a fuel gauge this week and see what it's saying. Been meaning to get one of those anyways.
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Old 04-30-2013, 05:38 AM
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Those plugs are DRIPPING in oil. Guides, rings, intake gaskets, INTAKE ROCKER STUDS NOT SEALED are my guesses. You should not have oily threads!
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Old 04-30-2013, 06:00 AM
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My first step of order would be to replace the plugs as mentioned.
However you can do yourself a favor, don't use anything with Accel written on it. I'm not saying this because I don't like Accel, I'm saying it out of experience. Years ago Accel went cheap and I mean real cheap.
Bought a new Accel HEI supercoil. it worked until the car reached 4300 rpm, then it would start busting. Checked the spark and it was yellow which means weak. Reinstalled Stock HEI coil, nice blue spark. Brother purchased 8 new Accel injectors for his 85 TPI Corvette, 3 out of 8 were bad. Myself and two friends of mine, our rides needed a tune up, we seen the advertisement for Accel cap and rotor kit on sale for $20. We all three bought a kit. Within a week, all three caps had melted. Nephew got 8 spark plugs, two of the 8 were no good. Got a set of plug wires, all had high resistance right out of the box. Needless to say, I usually give any brand a 3 strikes your out rule and I stuck to it. After getting burned three times I'll never use another Accel product again. I use AC Delco plugs. I have used Bosch Platnums as well as NGK's and had great service out of all three.
By the way your plugs look, it's difficult to tell if that's fuel soaked or oil soaked. Being that a couple have a white pattern on them kind of suggests oil, as usually if it's running too rich it effects all the plugs, not just some.
If it is in fact oil then go over the things suggested, but also check the intake for vaccum leaks around the gaskets. Also check the oil for fuel contamination.
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Old 04-30-2013, 06:51 AM
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I'm guessing you have some oil getting into some of the cylinders, though it could be fuel. How old is your engine, and how often do you change your oil?

BTW I'll repeat the already stated advice NEVER BUY ACCEL. I like NGK iridiums, but they're not cheap. If you want a cheap plug an ACDelco or a Bosch copper plug will usually work just fine.
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Old 04-30-2013, 08:59 AM
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Thanks for the responses.
This year I picked up Bosch Copper plugs. Have always used NGK Iridiums in my cars, but haven't for this one for some reason. Any recommended gap? AutoZone gave me 0.060" when I asked. Seems to be a good ballpark to be in.

Oil level stays the same for the whole season. Have never had to top off for the 3 years running now. Threads did have oil on some of them, not all. I did have dirty hands while handling them so in the pic, that may be the case on some of them. Oil has gotten changed each April. Haven't put too many miles on the car yet, so really haven't needed to change more often. This year will be different and may get one half way through or so. Drained oil had NO contamination in it of coolant or fuel.

Bottom end is near stock SBC400 from the 75. Only has 29k miles on it. Cam is upgraded. Pistons, rods, rings, crank... nothing besides the cam and the timing chain on the bottom was touched. Aluminum heads (no name) but were checked out by a shop after got them surfaced and were good.

Motor gets very very little white smoke out exhaust.

I'll have to check the Intake rocker studs when I do the valve adjustment this weekend. Would those being loose allow oil to drip into the camber?
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Old 04-30-2013, 11:45 AM
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.060"?! That's a lot, a good ignition may be able to handle it, but .040"-ish is more common.
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Old 04-30-2013, 11:47 AM
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Originally Posted by david-b View Post
Thanks for the responses.
This year I picked up Bosch Copper plugs. Have always used NGK Iridiums in my cars, but haven't for this one for some reason. Any recommended gap? AutoZone gave me 0.060" when I asked. Seems to be a good ballpark to be in.

Oil level stays the same for the whole season. Have never had to top off for the 3 years running now. Threads did have oil on some of them, not all. I did have dirty hands while handling them so in the pic, that may be the case on some of them. Oil has gotten changed each April. Haven't put too many miles on the car yet, so really haven't needed to change more often. This year will be different and may get one half way through or so. Drained oil had NO contamination in it of coolant or fuel.

Bottom end is near stock SBC400 from the 75. Only has 29k miles on it. Cam is upgraded. Pistons, rods, rings, crank... nothing besides the cam and the timing chain on the bottom was touched. Aluminum heads (no name) but were checked out by a shop after got them surfaced and were good.

Motor gets very very little white smoke out exhaust.

I'll have to check the Intake rocker studs when I do the valve adjustment this weekend. Would those being loose allow oil to drip into the camber?
being almost 40 years old will allow oil into the chamber regardless of mileage, I'd check your compression and leak down if you can.
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Old 04-30-2013, 03:44 PM
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.060"?! That's a lot, a good ignition may be able to handle it, but .040"-ish is more common.
I agree, 0.040" to 0.045". The wider the gap, the more coil it takes to jump the gap.
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Old 04-30-2013, 03:54 PM
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Aluminum heads (no name) but were checked out by a shop after got them surfaced and were good. Motor gets very very little white smoke out exhaust.
The plot thickens.
If the angle of the heads and the angle of the intake manifold do not match exactly, top to bottom, there is a possibility that the gaskets do not seal the ports on the heads all the way around the ports. If the ports are gapped open a little on the bottom, the motor can suck in oily vapors from the crankcase on the intake stroke. It could be 1 or more cylinders that are affected. Maybe some are sealed up while others are open to the crankcase. Only way to know is to look at the intake gaskets and verify that the gaskets are pinched all the way around the ports. That's why I recommend sacrificing a set of intake gaskets on the initial build. Torque the heads down for the last time, then install and torque the intake manifold. Let it sit overnight, then remove the manifold and examine the gaskets for being pinched all the way around the ports. If they are, great, use another set of new gaskets and torque the manifold on for good. If not, you have some machine work in your future.
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Old 04-30-2013, 04:01 PM
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I will pull the plugs are regap. Guess that's what I get for going off of Autozones computers.
Tech, makes perfect sense. Would have never thought of that. I don't remember the exact shave done by remember it was very little. But it would make sense though.

I'm going to try the fuel pressure gauge first and see where I sit with that. Figure knock out the easy stuff and see where I stand after that.

A lot of good information here, I appreciate all the help from everyone!
/D
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