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You definitely want to get new plugs in it, once they get fouled they are junk for performance use.

I would go back to the 6.5 power valves, the O2 meter is showing pig rich at "fast cruise" because the powervalves are now open when they really don't yet need to be since you are at part throttle still.
This also corresponds with the good 12.5 AFR at WOT, since fuel delivered at WOT is from main jet and power valve feeding together as designed.
Your powervalves are now "powering" when they shouldn't be, too early... LOL

Blip of hesitation at the hit of the throttle is pump shot, as indicated by the brief sharp lean reading spike that then catches itself.
This could be either a need for a larger squirter, or it could be just a need for a quicker rate accelerator pump cam on the linkage with the current squirter.

Did you happen to notice what color pump cams your carbs have on it??
 

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Discussion Starter · #42 · (Edited)
Orange cams on 2. I have a set of 35 squirters from a friend but didn't want to try until I get plugs.
I'm still learning so forgive me, but wouldn't the 6.5's just open sooner making it rich sooner? I don't quite understand that fix. It's my understanding they are closed by vacuum, so at idle (7-10) either would be closed. As I rev up, the vac goes up a bit first (so still both are closed) then drops to 0 and even into boost, so either would be open at that point but the 3.5 would be open later than the 6.5, no?

So I drove it about 7 miles to dinner last night and it did diesel still. Seems to be when things get hot enough, but the water temp was actually still cool and not even a hint of header glow (before timing, etc I did get a little header glow and that was just from around the block). Since i'm getting plugs today, could it need cooler plugs? What causes this? Current plugs BTW are NGK BKR5EGP

Forgot to mention (I think? I've said so much I'm not sure), if I manually shift, it doesn't seem to hesitate. I did that last night and holy #$# it's a different car! I was spinning tires, monstrous power and smooth. I beat a brand new Corvette at a light easy. Why is it so different in drive?
 

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Discussion Starter · #43 ·
Talked with NGK today, going to try the BKR6EGPs
Need to get those and oil. Looking for zinc oils, my local shop has Lucas hot rod oil. What would y'all think for weight?
 

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I'm still learning so forgive me, but wouldn't the 6.5's just open sooner making it rich sooner? I don't quite understand that fix. It's my understanding they are closed by vacuum, so at idle (7-10) either would be closed. As I rev up, the vac goes up a bit first (so still both are closed) then drops to 0 and even into boost, so either would be open at that point but the 3.5 would be open later than the 6.5, no?
You are correct.
I had a complete brain fart on that one, because I know better than that LOL. Can't for the life of me remember what I was thinking when I typed that.
It's got me focused on the "rich fast cruise" situation though, something is up with that. May be a situation where the main jet needs to be smaller for cruise and the power valve channel restrictions need to be enlarged to maintain the current good WOT fuel delivery.
 

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Discussion Starter · #45 ·
Thanks! I'm making tweaks and it's getting closer!
But, since it ran rich for a while it did this to the plugs. Got new (cooler as NGK said) plugs and oil/filter.
Household hardware Finger Nickel Auto part Engineering


Makes me think that's also in the valves/chambers? I have some Seafoam and n my garage, that stuff still safe for a motor like this?
 

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With good plugs in it just running with a good load it will clean the chambers and valves up. No need for the SeaFoam

One thing I will add though....you may find that the small wire/exotic metals (Iridium/Platinum) plugs don't last long in a high performance engine.
It is better to use a larger center electrode standard copper or nickel core plug.....the smaller wire plugs can't handle the extreme instant heat of WOT, despite their rated heat range the rapid rise in temp from a High HP WOT blast can melt them faster than they can shed the heat through the core and the base.
Maybe not as bad with a supercharger, I don't know, but with nitrous those thin wire tip plugs are worthless.

BKR5E,
NGK R5671A-8 the race plug closest to the BKR6E, just a half step warmer
NGK R5671A-9 is a half step colder than the BKR6E
Autolite Racing 3923 would also match the BKR6E
 
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