Sparkplug issue, kind of....

[Superscan811]

Anyone have any idea why the sparkplugs are like this.
On 1 side, they are all clean


On the other side, 1 and 3 are slightly fouled.


The fouling is only on the top 1/2 of the ceramic insulator.

I'm not getting any noticeable misses, I'm not using oil, not blowing any smoke.

Ideas???

Cheers.

[A112H]

I would say they are running a little cold and maybe a touch rich, but it isn't bad enough to worry about IMHO

[Superscan811]

My AFR is actually quite lean, around 17 on light cruise and 15.5 on 1/2 throttle.
I'm also using a slightly "hotter" sparkplug, NGK BPR5EY instead of the BPR6ES, which is standard.

To be honest, I'm more curious why only 1 side of the plug is fouled...

On No:3 plug, its about 1/4 of the way around the plug, on No:1 it's 1/3 the way around.

Curious....

Cheers.

[Torana68]

when the plugs are tight what does the dirty side face? inlet valve by chance?

[Superscan811]

when the plugs are tight what does the dirty side face? inlet valve by chance?

I index the sparkplugs so yes the dirty side is towards the inlet.

The head has:
1. new S/S valves.
2. new bronze guides.
3. new valve stem seals.

I can basically rule out wear.

The only other thing I can think of is the vacuum ports going to the PCV valve but that doesn't explain why it's only happening to 1 and 3...

Cheers.

[geezer101]

Unless the spark plugs were indexed it would only be by pure coincidence the plugs have fouled on the same side of the electrode. Is the distributor worn out? It could explain why it's fouled on the #1 and #3 only but not sure how. Just taking a wild stab at it...

[Torana68]

what spec is the engine? turbo? N/A?

[Superscan811]

what spec is the engine? turbo? N/A?

NA
9.6:1 CR
New build with around 15k on the engine.

Cheers.

[Torana68]

ok then the best bet is to pop the manifold and look at the backs and stems of the two inlet valves, if they are somewhet dirtier than the other 2 your problem is valve , guide or stem seal.... doent look too bad yet though. Std cam?

[Superscan811]

Std cam?

Stage 3 Camtech cam, the largest they can regrind a standard cam, so it's fairly mild.

ok then the best bet is to pop the manifold and look at the backs and stems of the two inlet valves, if they are somewhet dirtier than the other 2 your problem is valve , guide or stem seal.... doent look too bad yet though.

Took the rocker cover off today to check if the valves had any sideways play but all was good. The seals were also fine, no visible tears. I'll remove the carbs and look.

Cheers.

[Torana68]

carbs? you dont have to do much to damage stem seals, are they Mits or cheapies??? cheapies suck ! overheated it? that could do it as well, slightly off square when fitted..... blah blah.....higher lift cam can also cause issues with side loading of the valve/changes to valve geometry etc etc.....

[Superscan811]

carbs?

you dont have to do much to damage stem seals, are they Mits or cheapies???

Neither. The seals are a premium grade viton rubber.
I use the Cosworth Sierra valve giudes and seals.

higher lift cam can also cause issues with side loading of the valve/changes to valve geometry etc etc.....

I use Scat Swivel foot tappets which help minimize those issues, but, the "Stage 3" Camtech cam has a 1.9mm lower lift than a standard cam.



BTW: My engine build details..

Cheers.

[Torana68]

dak dak parts? good things those eliphant feet....