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Old 05-18-2023, 07:48 AM   #1
chrismoore701
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Fouling plugs

I am fouling plugs on cylinder 1 & 2. I am running NGK R5671A-7 plugs. Should I change these?

350 Gen 1 bored 40 0ver, 400 crank, 750 double pumper.

New build mostly idle time, around the block a couple times, but not driving daily yet
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Old 05-18-2023, 10:43 AM   #2
kwmech
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Re: Fouling plugs

The 750 double pumper may be putting too much fuel into the engine
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Old 05-18-2023, 12:21 PM   #3
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Re: Fouling plugs

Its not even started to break in. Verify timing and run it. Check the plugs again after a couple hundred miles.

Double check for a vacuum leak on the back cylinders. A brake booster can leak while still providing boost.
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Old 05-19-2023, 09:47 AM   #4
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Post Fouling Spark Plugs

It depends on how they're fouling ~ oil or fuel ? .

What's the gap ? .

Points or breakerless ignition .
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Old 05-22-2023, 12:32 AM   #5
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Re: Fouling plugs

VWNate1
Quote:
It depends on how they're fouling ~ oil or fuel ? .

What's the gap ? .

Should be HEI 43-45 gap. As said by VWNate1.
And I would use a vacuum Gauge to adjust the carb check the timing. Did you have the head seat seals changed make sure the plugs are not oiling fouled. Go back to basic re-ID: the plugs again to find out the problem.
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Old 05-22-2023, 07:30 AM   #6
chrismoore701
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Re: Fouling plugs

It is carbon fouled
HEI Distributer
I think the gaps are about 0.55
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Old 05-22-2023, 08:08 PM   #7
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Post Fuel Fouling Plugs

Okay ;

Now you're getting some where .

Time to check the timing and then look at the fuel system as carbon usually means running too rich and there are myriad simple reasons for this .
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Old 05-23-2023, 07:21 AM   #8
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Re: Fouling plugs

I have heard my carb is too big

Double pumpers are used for manual race cars, not drivers
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Old 05-23-2023, 08:01 AM   #9
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Re: Fouling plugs

New build, mostly idle time you said.
We’re assuming you did the required cam break in. Normally 2000 rpm for 20 minutes.
A double pumpers not too big. If the floats are set too high or the power valve is not the right one you can get a rich carb.
Lack of enough timing can cause fouling too.
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Old 05-24-2023, 07:24 AM   #10
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Re: Fouling plugs

I did the proper break in I have an 8.5 power valve & 73 main jet and a 77 secondary jet
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Old 05-24-2023, 08:11 AM   #11
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Re: Fouling plugs

What’s your idle rpm?
What’s your initial timing?
What’s the vacuum reading at idle?
What do the plugs look like on 7 and 8?
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Old 05-24-2023, 01:24 PM   #12
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Post Fuel Fouling Spark Plugs

Plenty of double pumper carbys are factory stock .

Yours -may- be too big, keep following the basic questions here, in my long career most times it will turn out to be a simple thing once you find it .
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Old 05-24-2023, 07:42 PM   #13
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Re: Fouling plugs

Hard to get a good plug read 'just idling'. Drive it 20 or so miles to a good place to eat, get lunch, come back and when it cools off, see what the plugs say. Plus it will be a good start on the break in process.
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Old 05-25-2023, 07:21 AM   #14
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Re: Fouling plugs

Quote:
Originally Posted by Dead Parrot View Post
Hard to get a good plug read 'just idling'. Drive it 20 or so miles to a good place to eat, get lunch, come back and when it cools off, see what the plugs say. Plus it will be a good start on the break in process.
That is the new plan

thanks
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