Reading Spark Plugs

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matthon

matthon

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I pulled my plugs today to get a read on them and educate myself. It seems to give off a stronger than normal exhaust smell, not too bad, always has. New exhaust out the back, new trunk seal, etc.

All the plugs have a light coating of oil on them, and I am perplexed.

383, rebuilt about 4 years ago, everything done, driven as much as possible, aluminum heads, accel distributor, 2 Holley 390s. It runs great, and very reliable. New pcv valve,and I checked it today, no oil in the line or carb (hooked to one of the carbs, not the air cleaner).
Engine has no oil on the outside except for an extremely small amount of weeping around the valve cover bolts. Intake bolts are tight.
Oil level and pressure is normal, no smoking exhaust, no oil in the radiator, no oil on the ground.

Any thoughts?

20170430_123911.jpg
 
Dead rich. I'm not a fan of those 390 carbs.

If you are using a TR you need to be able to change air bleeds, idle feed restricters and emulsion.
 
They are not wet with gas, no odor of gas at all. It's oil.
Rich or wet would mean gas on them?

Car was sitting overnight when I pulled them, if that matters.
I have a set of 600s, but I thought those would be too much carb.
Yes, it has a TR.
 
Reading plugs on pump gas with ethanol is all but impossible because of how light they burn.

But judging from your plugs, it looks like you probably have raw liquid fuel dumping out your tail pipes.
 
matthon said:
They are not wet with gas, no odor of gas at all. It's oil.
Rich or wet would mean gas on them?

Car was sitting overnight when I pulled them, if that matters.
I have a set of 600s, but I thought those would be too much carb.
Yes, it has a TR.
Click to expand...

The overfueling is probably washing the oil off the cylinder walls and collecting on the plugs.
Your original description of the problem says it doesn't use oil, so how else could it get there?
 
I appreciate the info. The fuel washing the oil off the walls makes sense.
I thought it was rich, yet I could not understand why the plugs didn't reek of gas or have any on them.
I was seeing oil, and it didn't seem likely that gaskets were failing on both sides, that is why I checked the pcv.

A friend of mine can probably help me sort this out, just needed some advice from those in the know.
Thank you FABO.
 
I'm bringing the 600s, new plugs, and cam specs to a competent friend/mechanic on Wednesday. I'll share this thread with him.

What is the difference between the 390 and 600 carb?
Is it that on a 600 you can change air bleeds, idle feed restricters and emulsion, 390 you cannot, or is there more to it? Not that I've ever done any of that myself, but I can learn.
 
matthon said:
I'm bringing the 600s, new plugs, and cam specs to a competent friend/mechanic on Wednesday. I'll share this thread with him.

What is the difference between the 390 and 600 carb?
Is it that on a 600 you can change air bleeds, idle feed restricters and emulsion, 390 you cannot, or is there more to it? Not that I've ever done any of that myself, but I can learn.
Click to expand...


The 390 doesn't have an accelerator pump (IIRC) and it's too small for a stock lawn mower.

Not a big fan of ANY vacuum secondary Holley carb. Also not a fan of a carb, especially in a 2x4 application that easily change the air bleeds, idle feed restriction, transfer slot and emulsion bleeds. You have doubled the needle and seat area, the jet area, the bleed area and the emulsion are. But you didn't double the air flow. You can't correct that with a jet. Also forgot, you need to be able to tune the power valve restriction.
 
I wanted to give an update and thank everyone again.
My friend rebuilt the 600 carbs, put in new plugs, and tuned it up.
It runs so much better, throttle response it better, it's a different car. The tunnel ram hesitation is, different, not better or worse, and nothing that affects drivability or is even noticeable to passengers.
It feels like if they were not vacuum secondary carbs it would run even better, at least more ridiculous.
It felt like I was stopping for gas more often at first, but now not so much.
Plugs still look good and the horrible exhaust smell is completely gone.
The electric chokes were swapped from the 390s, they worked fine when I picked it up, and he had it for a few days to sort everything out, however they haven't worked since. I only checked for power to them, nothing else. It's been very warm and a non-issue to date, but I will address it.
I would like to try it with mechanical secondary carbs, just to see how it drives, but it's not on my list of things to do right now.
I am happy to say, tunnel rams work very well on the street, and I drive this car daily - I mean as a daily driver everywhere I go, if it isn't pouring rain when I leave in the morning I take it.
Thank you again FABO!
 
It has been 16 weeks since the carbs were rebuilt. It has run extremely well and been a blast.
A few days ago I was sitting for what seemed forever at a light, when I pulled away it seemed to stumble and backfired through the carb or carbs, not sure with the air cleaner on it - but it blew the filter out the front.
The next day on the way home the rpms were very low in neutral, it didn't stall but close, so I turned the idles up to get home.
I noticed the carb/tunnel ram gaskets were seeping gas, so I tightened them up, next day I had to turn the idles back down.
I got new gaskets today and will replace asap.

It seems to not be running the same, but it's hard to tell. When I got to work today somebody told me, "It doesn't sound as loud today." Which left me perplexed, but reinforced that it felt like it was running different - it runs fine but not as much punch to it, hard to describe.

Can leaking carb gaskets also allow air in?

I also read on this forum that tunnel rams need to warm up thoroughly. My chokes have not been working since the carbs were rebuilt, but it has been extremely warm so it didn't appear to be an issue. Could that be a contributing factor?

I pulled the plugs, they all look the same, pics of one attached. How does it look after 16 weeks?

20170830_124145.jpg


20170830_124126.jpg


20170803_184934.jpg
 
It is definitely rich at a cruise. I can't see into the bottom of the insulator but I'd bet it's rich at WOT as well. Superformance makes the best gaskets for under the carb.

You probably need to use a smaller idle feed restriction and if the metering blocks have the IFR at the top of the well you need to move it down. You probably need to open the power valve channel restricters up so you can clean it up at a cruise. Without seeing the carb, I'd say you will probably need to install T-slot restricters.

We won't even get into emulsion. All the above will clean the carbs up a bunch.

BTW, in the section someone has 2 matched double pampers for sale. I'm not sure if they are TR calibrated, but on those carbs everything is adjustable and it's easy to do with those carbs.
 
Is there any oil or oil smell on the plugs this time?
 
What number are those plugs? They should be a RJ12YC. Those look like small block plugs. (LONG REACH)
 
I usually have no problem reading them, sometimes I need my reading glasses if the numbers on the porcelain are too small to see...
 
toolmanmike said:
What number are those plugs? They should be a RJ12YC. Those look like small block plugs. (LONG REACH)
Click to expand...


That's the correct plug TMM. In his OP he said aluminum heads. If that is correct it should take the long reach plug. He could run the N plug but it has the 13/16 hex. The C is the 5/8 and is much easier to use in almost any application.
 
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