Carboned up Spark plugs

I

Iowa409

Well Known Member
Supporting Member 3
So I have been running Autolite XP 64s Iridiumn (?)
On clean, new plugs after running maybe a total of 5 hours, I pulled them out to, excessive carbon.

I had the total timing set at 34, hose off etc. ran great really as far as performance, and smooth idlings.

I am running a MSD 6AL box, HEI MSD street Distributor, Blaster 2 coil, and had the plugs gapped at 40.
All new 8.5 MSD Super spark plug wires.

The carbon was the results at these settings.

Things to help in considering this:

Brand new Holley 670 Street Demon,No adjustments or parts changed yet, ran right out of the box. Stock everything.
New 7158 edelbrock small port intake, no pluggage or blockages, New Accel Fuel pump, Double feed inlet at carb, show5-6 psi constant.


As I put my top end back together, I am thinking about where I might make some corrections.

I am thinking of widning that spark plug gap to 50? Help ot hurt?

To much timing? AND mostly keep in mind, my rockers and lifters were set INCORRECTLY just a tad, which is why I am doing the work again.
I used that video Jeff sent over and it went perfecto, (I think lol, havent heard it run yet) I felt like it was easy once I truly understood the procedure.

I assume the timing might have been affected by that? maybe not, fire away with and thoughts guys, Im all ears.
 
MRHP

MRHP

 
Supporting Member 1
I would start with carb adjustments. Plug gap at .040 is good. timing seems good. I would also check fuel pressure, and float levels before anything else. Most likely some jetting.
 
boxerdog

boxerdog

Well Known Member
Supporting Member 5
I'm no expert, but I've never been a fan of iridium plugs for the kind of usage these old engines get. Even though MSD sells iridium plugs, I think they recommend against them somewhere in their documents. And I keep gaps under .040 usually, maybe .036 or so, again, it's just a habit.
 
I

Iowa409

Well Known Member
Supporting Member 3
boxerdog said:
I'm no expert, but I've never been a fan of iridium plugs for the kind of usage these old engines get. Even though MSD sells iridium plugs, I think they recommend against them somewhere in their documents. And I keep gaps under .040 usually, maybe .036 or so, again, it's just a habit.
Click to expand...
Yes Ive heard and been told the same info, I spoke to MSD and they NOW say its ok? wonder if that is because they now offer the iridium plugs?

Clarification: I had them set at 40 with all the carbon, I have now readjusted them to 50, I have not ran the engine yet, but I was running great at 40?? I am thinking with the blaster 2 I could run closer to 50-60?
 
32witha409

32witha409

Well Known Member
Supporting Member 3
Hard carbon build up is oil burning or lead from fuel, plugs that are just black with no significant layer is running rich or idling/low heat.
Photos of each plug would be super helpful in diagnosing.

As noted already, get it out on the road and run it hard for 10 mins so the plugs can get up to their optimum temperature. Re check
 
Last edited:
I

Iowa409

Well Known Member
Supporting Member 3
32witha409 said:
Hard carbon build up is oil burning or lead from fuel, plugs that are just black with no significant layer is running rich or idling/low heat.
Photos of each plug would be super helpful in diagnosing.

As noted already, get it out on the road and run it hard for 10 mins so the plugs can get up to their optimum temperature. Re check
Click to expand...
As Ive said before, It was running great and all carb adjustments are still set, other than timing obviously. BUT prior to the switch to the Holley 670, I had the new Edelbrock on there, but inlets were plugged, I missed it and never could get it cleared, so I changed out the carbs, so with the first carb there was alot of adjusting, tweaking etc., this Holley is very damn close out of the box, so maybe the plugs carbon were from that time period?
I have already cleaned the plugs so pics are out at this time. I would say NOT hard carbon but more like a a fluffy carbon almost powder and dust bunnies.
 
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