Spark plug diagnosis
 

Here is my spark plug I just pulled. Can anyone diagnose it? I think that there is oil around the threads but not on the place where the spark comes from.

Re: Spark plug diagnosis
 

Well, the tip /strap look tan....were the plugs loose? Next ?, what problems are you having with the engine? longhorn:chevy:

Re: Spark plug diagnosis
 

The plugs were not loose. The reason I was looking for some options is because I am planning on taking my truck to the dyno to get turned and I wanted to make sure that when I got there they didn’t tell me I needed new plugs and tell me to come back later. The problems that I seam to have are, hesitation at acceleration, spitting and stuttering, sometimes stalling, poor acceleration at wide open throttle. It’s not the timing. When I try to adjust the mixture screws using a vacuum gauge the adjustment of the screws have little to no effect. I have heard that most of those things can be attributed to needing different metering rods and or jets in my quadrajet.

Re: Spark plug diagnosis
 

Valve cover gasket leak? Combustion part of plug looks clean.

Re: Spark plug diagnosis
 

That might be the reason for the oil. Oil tends to come out of the breather right above that plug.

Re: Spark plug diagnosis
 

If the adjustment of the mix screws has no effect that tells you that the idle screw is cranked up enough to expose the idle transfer slot completely and you’re idling on the power circuit.
One of the cures is hooking the vac pot to manifold vac on the carb and advancing your initial timing. Both of those will allow the closure of the idle screw and the mix screws back working like they should.
Plug looks rich.
Rub it in your palm.
If the black is dry and sooty it’s rich.
If the black is wet it’s oil.

Re: Spark plug diagnosis
 

The black on the threads is wet

Re: Spark plug diagnosis
 

Is this the correct connection of the vacuum pot?

Re: Spark plug diagnosis
 

If so then my next step would be to advance my initial timing and then lower my idle which will allow me to adjust my mixture screws?

Re: Spark plug diagnosis
 

Can’t see either the vac pot or the hose on the carb end in the pic but can find another pic of your carb that shows the hose hooked to a ported vacuum source.
Hook it to that port covered by the blue cap down beside your drivers side mix screw. That’s manifold vacuum.
Then reduce your idle.

What’s your initial timing?

Re: Spark plug diagnosis
 

I thought this was the hose that connects the vacuum pot to carb. I think that was on the carb when I purchased it. The pot does engage after start up.

Re: Spark plug diagnosis
 

Sorry here’s the connections I was talking about.

Re: Spark plug diagnosis
 

This is what the timing was the last time I checked it 6 months ago.

15 degrees at 900 RPM
38 degrees at 3,000 RPM

I won’t be able to check it again until next weekend. If that photo is confusing I will try and get a better photo today

Re: Spark plug diagnosis
 

15 at 900 might be actually be 8 at 700.
You need to get your idle down as low as possible to check and set initial.
When working by myself I’ve chained my truck to a pole so I could get the idle down to 700.
No more pics needed.

Re: Spark plug diagnosis
 

Plug issue looks to be a leak in the valve cover or something around the plug. The internal part of the plug looks really good. All the other symptoms you seem to be having could be in the carb, timing or something like that. I don't think your plugs or the heads are bad if all your plugs look like that. Maybe your EGR valve if you have one?

Re: Spark plug diagnosis
 

So the goal would be to set the timing at around 700 rpm. In order to do this I would have to have the truck in drive? That is why you are talking about chaining it to a tree? So that I can keep it in drive and it won’t run me over. What should I set the timing at when it is at 700 rpm? How will this help me to turn down my idle adjustment screw?

Re: Spark plug diagnosis
 

I don’t believe I have an EGR valve. Thanks for the help.

Re: Spark plug diagnosis
 

I chained it, you don’t have to.
Find somebody you trust, put the park brake on, have them hold the brakes down and put it in gear then check your timing.
Or just turn your idle down. If it wants to quit just advance the timing a touch. Leave the distributor loose enough to move but tight enough to not move on it’s own.
Once you find out what your actual initial is then set it at 14 and lock down the distributor.
Try that and tell us what your actual initial is.

Re: Spark plug diagnosis
 

Will do. I will get back to you with that next weekend. I don’t live where I keep my tools and work on the truck.

Re: Spark plug diagnosis
 

That is so funny! Done the same haha!

Re: Spark plug diagnosis
 

I tried that chain trick once, but the truck just kept dying. So I locked it in 4-Low, when I let out the clutch ...it pulled the tree down :confused:

Re: Spark plug diagnosis
 

I took a photo of how much thread I had on my idle set screws. Dues it look like I have enough left to lower it so that I am not idling in the power circuit? If I lower my idle so that it is not idling on the power circuit, how do I get the idle back up?
I wish I could get a better photo but it gets dark in there and taking a photo that close tends to get blurry.

Re: Spark plug diagnosis
 

Being upside down probably doesn’t help either.

Re: Spark plug diagnosis
 

I wrote it in post #18.
Back off the idle screw and add more initial to keep it idling.
More timing at idle increases your idle.

Re: Spark plug diagnosis
 

Okay thanks. Is there an amount of advance that I should not go over when doing this?