excessive carbon buildup on plugs after short run on 2.5 drag??

[stoker2001]

just when I thought I seen it all..
motor surges intermittent at all RPMs
I run aftermarket heads with removable chambers,one of the chambers cracked and was pressurizing water jackets
I replaced all the domes,but maybey I am ingesting water now??
I run 60% AV 100LL and 40% pump91 and run real fat with A6 box at 105%
all 6 plugs look same as do all 6 piston tops
if I was ingesting water,could it get in all six holes evenly from defective divider gasket??
stator ohms out fine and all six jumping 1/2" gap with spark tester
plugs are Nippon denso fine wire Iridium IW27 =to 9 heat range NGK
this is river running at 6-7000+ RPMs for 60 miles..pulling my hair out

[StratosVT]

The pic of the plug looks like pieces of porcelain missing. Is it a bad pic or is the plug damaged?

[StratosVT]

Definitely would look at the aftermarket heads to make sure they are sealing properly....looks like they may not be.

[patchesII]

Kevin, do you have another set of heads you could try

[stoker2001]

Kevin, do you have another set of heads you could try

nope
I have used these Rivers heads for years swapping loose and tight domes and never had issue.the new 29cc set that I just got from geigertech fit like a glove and squish came in at .040.leakdown all at 4-6%

[stoker2001]

The pic of the plug looks like pieces of porcelain missing. Is it a bad pic or is the plug damaged?

no damage or Porc missing,thanks Harry

[stoker2001]

Definitely would look at the aftermarket heads to make sure they are sealing properly....looks like they may not be.

the orings in domes would have to be leaking,and I just don't sense it after good comp and leakdown test...

[stoker2001]

might be switch boxes double firing??can this prob be intermittent?i index my flywheel to check timing on all six and seen it with timing light once,then it went back to normal..
one thing I am noticing is 3-4 degrees variance in timing with #6 being high..
I did all the Peak DVA readings while cranking engine and the all fell on low side,but within spec per book

[motorheadbishop]

Surprised motor will even turn up at 105%
That's definitely your surging problem, and your piston top also shows (SUPER FAT)
put box a 102% and run 91 or 93 with a shot of aces (1ounce to 5 gallons)... should go away...

We ran into the same thing a year or so ago, and was mixen 5 gallons avgas to 15 gallons 93...
Switched over to aces and it went away...

BUT funny thing was we had ran that blend for a while and it never did that... Then all of a sudden
it happened we switched over to Aces it was gone... NOW, I have ran outta Aces and went back to that
mix again (av gas and 93) when I didn't have a choice, and it was fine... Always thought maybe it was the
batch of fuel, but you would think being Aviation fuel it would always be top quality... Just my experience...
GOOD LUCK!!!

[stoker2001]

Surprised motor will even turn up at 105%
That's definitely your surging problem, and your piston top also shows (SUPER FAT)
put box a 102% and run 91 or 93 with a shot of aces (1ounce to 5 gallons)... should go away...

We ran into the same thing a year or so ago, and was mixen 5 gallons avgas to 15 gallons 93...
Switched over to aces and it went away...

BUT funny thing was we had ran that blend for a while and it never did that... Then all of a sudden
it happened we switched over to Aces it was gone... NOW, I have ran outta Aces and went back to that
mix again (av gas and 93) when I didn't have a choice, and it was fine... Always thought maybe it was the
batch of fuel, but you would think being Aviation fuel it would always be top quality... Just my experience...
GOOD LUCK!!!

appreciate feedback
I just cant buy into aces and Pump premium 91(calif) with 175 PSI cranking river running WFO for miles and miles..
I have run box at 105% in past with no prob turning 30 pitch 8200,so still chasing prob?
so strange that the plugs are building excessive carbon with one outing (65miles)but pistons aren't??
I might have two thing going on at once?seems weird that the prob came up about same time I installed these new removable domes..might try 100% AV gas next run..?

[stoker2001]

found part or mayby all of my probsleaky #6 injectorgo figure,i had this set flowed and cleaned last spring..also run expensive Kinsler pre and after fuel filters..crazier things have happened!I don't run basket/inlet filter screens on injectors (mercury racing bulletin back in 1997)..mayby I should rethink this?