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My spark plug colors, am I good or not?

13K views 46 replies 10 participants last post by  bubbahotep 
#1 ·
Below are 2 of my plugs on a carb'd 383 stroker. These are accel 276s shorty plugs for headers. According to accel, they are HOT plugs (they claim that the last digit is the temp ranging from 1 to 8?? and these are 6). These are NON resistor with an msd6 and coil

The pics should show that the white center part is black but thiny covered and the electrode part looks lighter. Any oil that you see is from the valve cover oil that sometimes runs down when I dont seal it good

So my question is, do you think Im running ok or am I too lean / too rich / or is the plug wrong? I was thinking of going with a cooler plug with a resistor???



 
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#2 ·
bubbahotep said:
Below are 2 of my plugs on a carb'd 383 stroker. These are accel 276s shorty plugs for headers. According to accel, they are HOT plugs (they claim that the last digit is the temp ranging from 1 to 8?? and these are 6). These are NON resistor with an msd6 and coil

The pics should show that the white center part is black but thiny covered and the electrode part looks lighter. Any oil that you see is from the valve cover oil that sometimes runs down when I dont seal it good

So my question is, do you think Im running ok or am I too lean / too rich / or is the plug wrong? I was thinking of going with a cooler plug with a resistor???



These plugs show either or combinations of the following:

1) A little rich

2) Plug a little too cold

3) Engine doesn't get warmed up

4) Not driven very far

5) Not driven very fast

6) Compression not high enough

Bogie
 
#4 ·
cobalt327 said:
The center two plugs (especially) seem to have some small spheres of aluminum. I hope that's not what it really is- I've "doctored" the images to make them a little easier to see.

My left to right is your top to bottom:
That's just fuel chemistry, if this was lean, or the cylinder in detonation/preignition, the insulator would be white (if not white, white) and if the spots were melting aluminum off the piston that would appear as dark splotches on the insulator.

Bogie
 
#7 · (Edited)
Thanks for the opinions. Those 3 photos are of the same 2 plugs from different angles. Sorry I didn't mention that

Car is never warmed up, been started all winter on weekends and then shut off after 10 minutes

Driven 10 miles, maybe, per month this winter

These facts combined, are those plugs not used enough to determine the tuning?

Also, there's a 574s plug with a resistor and a 576s as well. Ones hotter than the other. I wanted to try a resistor plug with my setup. Yes, no? MSD 6, 38' locked out timing but computer controlled 20' timing at idle, MSD coil + wires, 9.7:1 compression

EDIT: Any odd metals that might be on the 2 plugs shown are from crap thats on the work bench.
 
#10 · (Edited)
bubbahotep said:
Any odd metals that might be on the 2 plugs shown are from crap thats on the work bench.
That's good. If it were aluminum, it would be troublesome.

What you don't want to ever see (images below) are extreme examples like these. Detonation and/or lean F/A mixtures are more likely to "pepper" the porcelain w/Al or material from the ground strap- or both, for that matter:
 

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#11 ·
Those are some damn ugly plug pics posted

Ive driven the car at about 80mph on those plugs but just regular driving in the winter for a short distance to take a ride and didnt do it the way mentioned.

Ive had occasional hot start "kick back" issues and was thinking the plugs were heated hot and causing the cylinder to fire before it got spark when it tries to start. Was hoping my plug pics would confirm my guess but maybe with the little use the car see's I cant really judge. Im convinced its NOT an ignition issue as I have an MSD timing computer, new wires, new distrib cap and rotor, and once started the timing is dead on accurate.

Also, my plugs appear to have carbon (black) on the center ceramic and theres little resistance between the center probe and the ceramic because of the carbon. That cant be good. New plugs of the same type will only result in the same situation I think. But looking at the pics you guys are posting makes my plugs look pretty.

The carb is a holley and pretty well tuned. The engine shakes so much at idle its hard to get an accurate fuel flow out of the side holes. Ive got all of 12hg vac from the idle screws which according to Holley is the way to check for proper setting (highest vac)
 
#13 ·
bubbahotep said:
The engine shakes so much at idle its hard to get an accurate fuel flow out of the side holes. Ive got all of 12hg vac from the idle screws which according to Holley is the way to check for proper setting (highest vac)
Hot kick-back can be from a lot of initial timing or even a battery with less than good condition or charge.

As for the engine shaking badly @ idle- are we to gather from this that you have a radical cam?

If that's the case, the plugs will look much as what you've shown until you are actually loading the motor and using it at the RPM that the cam's designed for.

Below that speed, and especially @ idle, a big-A cam will wreak havoc on plug reading- they'll soot up and generally be all but unreadable.

I'd suggest you sort the tuning as best you can (like you've already done, for that matter) AFA total timing and safe jetting goes, then go put some miles on the engine.

If you do this ending w/a "plug chop", you will get a much better indication of the tune from your plugs.
 
#14 ·
Yeah this is a radical cam lift 510/512 with duration at 236/246 if I remember. Its a street driven 383 stroker with 6500 miles on the entire drivetrain and ignition system is practically new from head to toe

Battery is a few months old red optimum, timing is retarded at start by an MSD ignition/advance computer and an msd6 box. MSD high torque starter is a few months old but prior to that I had a 10 year old summit starter. Total timing is 38' but only when its programmed to advance (no weights in the distributor). I idle at 18' and I could idle at 38' full advance and still not get a knock or ping.

The only old part is the plugs which I thought I cleaned off over a year ago and thats what you see here after 1 year of very little use. Not more than 10 miles at a time and few tire spins

But from the opinions Im seeing it seems my plug readings are not valid.

On a cold start with no choke mechanism I can fire up on a freezing cold day after sitting a week with no problem. Idle is rough until a few minutes and its warmed up. Same goes for starts on hot days after sitting a while. Its when I try to start after driving, park for 20 minutes for example, and then go to start I sometimes (50 50 chance) get that starter wurrrrr where you can tell the cylinder fired and is trying to spin the engine backwards. And if I let off the starter during the time the engine attempts to pop backwards.

After start the car runs perfect and timing is dead on, throttle response is tight and she moves without hesitation.

I agree it appears as a timing issue but MSD techs swear that their computer is retarding me 20' which would be 18' start timing (because Im locked at 38'). And why would the problem be on HOT starts only and never on a cold? Ive made posts about this on here before.

So, that leads me to the plugs which are NON RESISTOR + Hot type plugs. My guess was that maybe the plugs, when warm, are causing some ignition interference and I hoped that the colors would indicate that the plug is wrong anyway.
 
#16 ·
#17 · (Edited)
hey i didnt save that thread -- it was a good joke while it lasted-- :welcome:
what was nice was every one was a gentelman and didnt go off the deep end --that evening the mod called me and ask if i had a son and was my car ok--
some times we take life to serious and its fun to pull some ones chain --

i was serious about his timing --its to far advanced- and his motor should not shake all over the engine bay-- and good lope is different than shakeing--
id be worryed about the kicking back on the starter--
 
#18 ·
The fact it will fire right up with no Choke on the coldest day means to me she is way rich.How much of your idle transfer slots are exposed at the base idle setting? They should appear square when looking from under the carb not have the blades open so far they appear rectangular. It sounds like with your cam you have the throttle blades opened to far in order to get an acceptable idle causing it to be pulling fuel from the main metering circuit instead of just the idle cicuit.
 
#19 ·
barnym17 said:
The fact it will fire right up with no Choke on the coldest day means to me she is way rich.How much of your idle transfer slots are exposed at the base idle setting? They should appear square when looking from under the carb not have the blades open so far they appear rectangular. It sounds like with your cam you have the throttle blades opened to far in order to get an acceptable idle causing it to be pulling fuel from the main metering circuit instead of just the idle cicuit.
Hmmm, something I never thought to look at. Didnt think Id have a problem with the 12hg of vac I have and I have no partial throttle problems which I thought was a sign of a problem

When I say that it fires up, keep in mind I have to give it a pump of gas and hold the pedal down partly or she'll stall until warmed up. But it will start in a second and so long as I keep the rpm high enough it wont stall until warm and then I can idle at 900rpm or so.

I gotta pull the carb and see whats doing from underneath. At least its 1 less thing to guess about
 
#20 ·
If my wife knew I snuck into the garage on MOTHERS DAY I'd be dead.

Anyway, here's the pic which is hard to view because I cant focus on the openings:



The openings are NOT square and if I had to guess Id say theyre way over .070 or more. I think .040 is the ideal? Theyre not hugely rectangle but you can see the left side one a little better than the right. I wish I could get a better pic and will try. But Id say its close to twice "long" on the opening as it is wide. Follow me?
 
#22 ·
I got a better pic, hope it has more detail than the enhanced one above



You can see the long opening and theres also a tiny tiny little round hole just above the plate which, if my openings were SQUARE, would be covered I think. In the photo, the left plate, you see the rectangular opening and to the RIGHT of that is a little shiny spot. Thats the little opening which would NOT be exposed.

Looks like I got issues here?? lol
 
#24 ·
The puzzle comes together now: I remember I used to have the idle timing at FULL ADVANCE of 38' before I installed the MSD computer for timing. It was hell on the starter but the car never had a problem. A few years back I installed the MSD computer, keeping the locked out timing of 38', but the computer can control the idle time which I have at 18 or 20'. With the lower timing I remember I had to bump up the idle screw and thats partly why Im too rich now

So, this week I think I'll just adjust the MSD computer to give me 38' timing at idle (the car never pings), then lower the idle speed screw, remove the carb, and see where I am?? YES or NO?

Or should I do the old trick of holes in the plates or fiddle with the secondaries to let more air in??

Which way is better?

Old rule was "get the highest possible timing you can without detonation" and I know I can go beyond 40' with no problem. 38' was recommended
 
#25 ·
Close the primaries till they are approx. square, open the secondaries slightly and try it before drilling the blades.A lot easier to drill out material than put it back in. Does you timing box have a start retard feature if so you could lock the timing and use it to start it to keep from hurting starters.
 
#26 ·
the MSD has a built in 20' start retard. I'm at 18' start no matter what because I'm locked at 38'

Once I set the plate back to where it's supposed to be, then adjust secondaries, where do I get my increase in idle rpm from? I'm exactly 1 full turn less on the idle screw to get the plate back. Is advancing my timing my only means of raising the idle speed?

It's no issue I just want to confirm it as such. Or will the secondaries be taking care of the needed rpm??
 
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