Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Engine, ignition, fuel, cooling, exhaust

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crazzmc
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Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Post by crazzmc »

Hi guys,

I know that these symptoms have been posted on the internet everywhere I just wanted to ask a few questions before I dig in deep. I've read a lot about how it's probably my head gasket seals that are bad, but people said that usually where the seal is you'll have a different looking spark plug. All my spark plugs are quite black, some are dry-ish some are wet-ish and some are kinda sooty with black particles, but overall quite consistent. I've replaced the Oil it was quite black, but didn't smell of fuel when i took it out. Put 5W-30 in as a few people recommended it for my 302. Same issues no increase no decrease in smoke. I pulled the valve covers off, no excess oil there so no holes are plugged up. Does anything think I could just be running rich? The guy that I bought it from really didn't know much and didn't change anything, but he said the guy before him had swapped the motor for a rebuilt 302 (apparently only has 6k miles on it), it has a Holley Carb and a Summit Intake Manifold. I'd rather be safe than sorry, I did get the truck at a good price it's a 1968 F-100 SWB. It wasn't smoking before, not that I noticed when I test drove it and I didn't really smell gas. I did drive it 100 miles back home, and started noticing it there, its a automatic converted from a 3 on the tree.

I haven't run a compression test because I (and yes I am am completely new to all of this and learning as I go) don't know how to safely disengage my ignition. I've looked at diagrams, but I can't figure it out and there are no videos online showing how to. I think it's either running rich, the head gaskets, or my worst fear the piston rings.

Any insight would help, I'd rather learn more before taking it to a shop and lose a bunch of money.

Thanks everyone,

Crazz
Figuring out this whole restoring process with my 68' F100.
71Fe2O3
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Re: Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Post by 71Fe2O3 »

It wouldn't hurt to adjust your carburetor if you think the engine is running rich. If you have a vacuum gauge, hook it to a manifold vacuum line and adjust the carburetor to maximize vacuum. If that doesn't make things any better, take off the top and see if the float is still floating-old floats can get holes in them and sink, which allows excess fuel into the intake.

There are several ways to prevent the engine from starting when you crank it. One very easy way is to remove the wire that connects the central post of the distributor cap to the coil. Also, you would need to remove the spark plug wires to do a compression test-the engine can't start without them.

A leak-down test will tell you more about the condition of your engine than a compression test. To do a leak-down test you pressurize each cylinder in the TDC position and measure how much air leaks out, you can also listen for where it leaks to. It can tell you if you have leaky rings, valves or head gaskets. The device isn't very expensive, and directions are readily available.

I suspect that most folks use a thicker oil than 5W30 in old truck engines-these things have looser tolerances than modern engines and were designed with thicker oils in mind. It is hard to say with certainty what is "best," but you will likely have better oil pressure with a higher viscosity oil, at least 10W30 or 10W40-some people go up to 15W40. I use 10W30 in winter, 10W40 in summer.
Fred

1970 F100 4WD short bed, 360 engine, very rusty plow and yard truck

1971 F100 2WD long bed, 302 engine, on the road

1968 F100 2WD long bed, 360 engine, stripping for parts
crazzmc
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Re: Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Post by crazzmc »

thanks for all the info. I've been watching some videos recently on the leak-down test. I'd rather be safe than sorry when doing any of these tests. I'll probably put 10-30 in the winter as I saw many people do that during the colder seasons. I'll keep you posted on my progress, just trying figure out what's wrong with my babe haha.
Figuring out this whole restoring process with my 68' F100.
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MadMike
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Re: Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Post by MadMike »

What intake manifold gaskets were use?
Smell the spark plugs, if they are more oily than gas smelling then I would suspect the intake manifold is not properly sealing and its sucking oil.

Summit intake manifolds were made by Professional Products, Chinese knockoffs of Edelbrock, Weiand, etc. I would not trust the quality of the intake manifold, it may not be properly machined and may not be square/properly machined with flat mating surfaces.
-Michael
crazzmc
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Re: Black Spark Plugs, White Smoke & Gas Smell from Exhaust

Post by crazzmc »

MadMike wrote:What intake manifold gaskets were use?
Smell the spark plugs, if they are more oily than gas smelling then I would suspect the intake manifold is not properly sealing and its sucking oil.

Summit intake manifolds were made by Professional Products, Chinese knockoffs of Edelbrock, Weiand, etc. I would not trust the quality of the intake manifold, it may not be properly machined and may not be square/properly machined with flat mating surfaces.
I haven't taken off the intake manifold yet, I've been quite busy at work. I will be working on my truck tomorrow night so I'll take some pictures for you guys then.
Figuring out this whole restoring process with my 68' F100.
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