BLACK SOOTY PLUGS

[fryedaddy]

i bought some new plugs for my 428,i was going to keep the old ones in order but there was no need to.all 8 were black covered in soot,no oil,just black soot.i have a new 850dp with straight 80 jets all 4 corners.i think it had 76s in the front new but i put 80s all the way around because thats what my old 850 came with and it ran great that way.what should i do to correct this problem with the black plugs?

[GerryP]

A hotter plug would probably help.  How are you using the car?  An engine operated at low speed and idling a lot will soot up the plugs even with a good tune up.

[fryedaddy]

3924,i hate to go any hotter because of engine mods and 100 shot.a lot of short trips around the block,not much idling if any.i run it pretty hard when i get it out but i dont stay out long.5 miles or less trips mostly.i was hoping a jet change would help.850dp,eld rpm,bbm heads,.245 flattappet cam,hooker,msd,etc.10.7 -1.i was told i need the 3924s.

[GerryP]

That's just a pretty common "go to" plug for use in alloy heads.  It isn't the ONLY plug you can use.  The plugs will be sooty the way you are using the car.  I know.  I do the same with mine.  You are using the jetting you have because you indicate the engine favors that jetting.  So be it.  If the plugs are firing fine, then just ignore the soot.  As long as you don't have any significant deposits --like ash you get with oil burning-- then just live with it.

[fryedaddy]

i understand,thank you Gerry.

[Katz427]

I have found that a carb change even, if CFM is supposedly rated the same, usually  requires a jetting change. Another thing is air bleeds, and the idle feed restriction. I have had to change airbleeds, and reduce the idle feed restriction, ( why do they make the idle so rich, out of the box? ) . So,I suggest, do all your checks, fuel pressure, float level, then check, out the idle fuel restrictions, and air bleeds ,  and see what you find.  You may have too , make some changes. Then watch a video from DragBoss Garage, with Mark Cambell. Mark was a Holley engineer, back in the 70's and explains some of the differences. Hopefully  Drew sees this, and responds.

[6667fan]

Might try some NGKs if you are changing out the plugs. They are not magically going to eradicate the soot situation. I think that is between the carb and how you use your machine.
V-Power Racing. R5672A-8. Stock number 7173

   

[Tunnelwedge]

Unleaded gasoline contains toluene as much as 35% in some pumps. They use it to cut gasoline and get rid of the byproduct (toluene). It burns sooty, but it is an octane booster. It's also quite nasty.
The higher the grade of fuel the more toluene it will have.
The more fuel you burn the more toluene you will burn and more soot you will make.
I have good success with NGK BKR6E  6962 in my BBM's making as much soot as I can.

[fryedaddy]

Unleaded gasoline contains toluene as much as 35% in some pumps. They use it to cut gasoline and get rid of the byproduct (toluene). It burns sooty, but it is an octane booster. It's also quite nasty.
The higher the grade of fuel the more toluene it will have.
The more fuel you burn the more toluene you will burn and more soot you will make.
I have good success with NGK BKR6E  6962 in my BBM's making as much soot as I can.

I have been running 93 no ethanol with 1/4 110 race fuel mix,i bet its loaded with that stuff your talking about.i have been wanting to try some NGKs.now that i have a part number,i will get a set.

[Nightmist66]

The plugs in the picture are resistor and are a 6 heat range. It's a pretty hot plug if you're going to run hard, especially with nitrous. If you want a non-resistor plug from NGK, I would recommend a 4091/ R5671A-7. It's a 7 heat range. We've had good luck with them at 12.5-13.5:1 compression with aluminum heads.

[fryedaddy]

i took my 850 apart and cleaned it,and i put a new set of NGKs in it.fired it up and it run like crap,backfire,no idle,awful.i thought i might check my msd plug wires with my ohms meter.and half of my wires were dead.i got a old set out and found enough good ones to make 8 total.fired it up and it ran like a top.smooth,crispy.i ordered a new set from summit last week,they were out of stock on the ones i tried to order,the sales rep suggested another set and sent me the wrong ones,they had male ends on dist end,and they dont fit the male ends on my MSD dist cap.i wondered why he asked my engine size,he must have looked up a set for a stock distributor.

[6667fan]

What’s that old adage about ignition vs fuel problems,? lol.