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Check this plug out

vintage chromoly

Well-Known Member
Local time
2:05 PM
Nov 13, 2010
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Hello all.
Thoughts on this plug.
The color doesn’t look bad, but all the plugs are wet like this after sitting for a couple days.

The car smells rich at idle, but if I take anymore fuel out of it it wants to stall.

Car is a mild 446. 20 degrees initial and 34 all in.
906 heads. Fully worked and in good repair.

Old school TRW forged flat top replacement pistons.

Solid flat tappet Crower custom grind cam. Pulls 14” of vacuum at idle.

Car is a David Braswell Holley 850 HP. Not specifically set up for this engine, but the car runs good and pulls hard.

Trying to figure out why it smells so rich at idle.



I would look at changing the idle air bleeds to a leaner bleed. Then turn the mixture screws accordingly, also check to make sure the float level isn't too high. And make sure the transfer slots are open at about 1/4 turn from fully closed.
I would try stock plugs. It is possibly also quite rich in the idle and transition circuits.

I found my 340 did not like side gapped plugs.
Is this a new build and you just don't have a baseline yet or have you recently made changes and now you are figuring it out ?
High initial advance, low vacuum, rich smell.....more info.
I have the idle screws at 1-1/4 turns out.
Transfer slots are square.
I stepped the IFR’s down form .033 to .031. I left the IAB’s alone.
The primary throttle plates are drilled. I just ordered some undrilled from Braswell today.
Idle vacuum is 14”.
20 degrees initial, 34 all in by 2200RPM
Pertronix ignition.
TTI 1-7/8” headers.
Manual transmission.
Float level is set to the bottom of the sight holes.

This is a newer setup. Trying to figure it all out.

Thanks fellas!
Maybe its something to do with the power valve. Just a thought.
I'd swap the carb and see what happens

I never had much luck with Hollys on any street application

Carter/Edelbrock style NEVER let me down, pretty much "set it and forget it"
The place to start is the primary main jet. This will influence all other AF's of the idle and transition.

Is it getting to much fuel from the secondary side??
It has 76 mains in it now.

I’ll give some 74’s a go.

Could be, on a secondary side.
It has 4 corner idle, and the T slots are square in the back.
Maybe its something to do with the power valve. Just a thought.
Had a PV just last week that was seeping through the diaphram. Still worked but was wet with fuel in the vaccum side of carb. Was real stinky at idle.
It runs well everywhere. It just stinks, and the plugs look wet to me. The color doesn’t look bad, but they are wet.

I’ll check the power valve.

Thanks for the ideas, fellas
how does it start 10 minutes after shutdown? is it loaded up?
It fires right up.
Like I said, it runs well. Just smells rich and the plugs all look like the pics
This is the carb build sheet.
It’s a Braswell carb, but has subsequently been gone through by a third party.
This build sheet is from the 3rd party, not David.


The obvious question: if you turn the mixture screws IN, does the engine stall?

- if it does, then the mixture screws, IFR & IAB, whatever size they are, are NOT the problem. Nor is there extra fuel getting into the engine [ from leakage ] if the screws will stall the engine.

- if the engine does not stall, then it could be too much transfer slot exposed, nozzle drip, leaking PV diaphragm, etc.

IABs &/or IFRs are not changed for the idle, like many people mistakenly think. There is always enough fuel for idle with the stock IFR. IFR also feeds the T slot, which controls off idle & low speed cruise. IFR is sometimes enlarged for THIS, not idle. IAB controls where the idle cct falls off.
Then I would say that because the car smells rich at idle, your smell is due to the large overlap of the cam. Nature of the beast when using a carb.