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persistent spark plug fouling

Old 12-16-2018, 11:16 AM
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Japery
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Default persistent spark plug fouling

Im having problems with my spark plugs.Ill start with what my engine is first. I have a Blueprint 355 engine with Edelbrock manifold and 650 carb. I have a DUI distributor with MSD wires. Everything is new. Im using Champion 792 with .045" gap(which is what they suggest using). Car runs kind of rough and has poor throttle response. I then tried to start again but wont because the plugs are wet and fouled.I tried tuning the carb so it wouldnt run so rich but i still get a rich condition. Any help would be greatly appreciated. PS. I tried to search this forum but could find anything.
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Old 12-16-2018, 11:49 AM
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MelWff
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two things come to mind, float level too high and why are you running such a cold plug? A 792 is a C59YC. The heat range of 59 is recommended by Champion for engines with a 13.0:1 to 14.5.0:1 compression, see page 5 and 6 below.

https://www.gsparkplug.com/media/wys...ence_Chart.pdf

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Old 12-16-2018, 11:51 AM
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I believe thatís a cold heat range racing plug. Probably need a hotter plug to burn off the deposits for everyday driving.

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Old 12-16-2018, 12:03 PM
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Blueprint engines recommends these plugs and used them at the dyno, Also my compression is 10 to 1
  • Cam Type: Flat Tappet
    .480 Intake .486 Exhaust
    229 Intake / 230 Exhaust duration
    @ .050

Last edited by Japery; 12-16-2018 at 12:09 PM.
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Old 12-16-2018, 12:06 PM
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Iv tried other plugs that where in the hotter ranges at no avail. I bought a 7lb mech fuel pump,do you think i should use a fuel pressure reg? should I try diff. needle sizes in cab? Is carb to big?

Last edited by Japery; 12-16-2018 at 12:24 PM.
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Old 12-16-2018, 12:25 PM
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Which pump? STock needle/seat size is fine.
Use a stock heat range spark plug, try that first bet it solves your problem. 650 is the perfect size for what you got.
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Old 12-16-2018, 12:44 PM
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Originally Posted by Japery View Post
Im having problems with my spark plugs.Ill start with what my engine is first. I have a Blueprint 355 engine with Edelbrock manifold and 650 carb. I have a DUI distributor with MSD wires. Everything is new. Im using Champion 792 with .045" gap(which is what they suggest using). Car runs kind of rough and has poor throttle response. I then tried to start again but wont because the plugs are wet and fouled.I tried tuning the carb so it wouldnt run so rich but i still get a rich condition. Any help would be greatly appreciated. PS. I tried to search this forum but could find anything.
Timing curve is off. My 2 cents.
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Old 12-16-2018, 12:44 PM
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Take the air cleaner off and look down the carb with engine running. Do you see fuel dripping/pouring down?
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Old 12-16-2018, 12:55 PM
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Originally Posted by Japery View Post
Iv tried other plugs that where in the hotter ranges at no avail. I bought a 7lb mech fuel pump,do you think i should use a fuel pressure reg? should I try diff. needle sizes in cab? Is carb to big?
Did you ask Blueprint what they think?
Did you measure the fuel pressure, Edelbrock carb has a maximum of 6.5 psi?
Did you set the timing to what Blueprint recommends, 34 at 3,500 rpm?
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Old 12-16-2018, 12:57 PM
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I bought the 7lb summit racing fuel pump for a 350 CSB
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Old 12-16-2018, 01:00 PM
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The car is at the mechanics and he cant really pinpoint what the issue is either. Ill check that on monday. Thank you
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Old 12-16-2018, 01:07 PM
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Which 650 do you have? Post #8 gave me an idea common to Holleys.
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Old 12-16-2018, 01:09 PM
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I think my first step should be to install a pressure gauge and see whats going on before the carb. Thoughts?
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Old 12-16-2018, 01:49 PM
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edelbrock AVS2 series
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Old 12-16-2018, 01:54 PM
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Ok, never mind. I really doubt this is a sparkplug heat range issue right now. You are flooding. And no certain sparkplug is going to help you.
Why are you flooding? IDK Raw fuel is entering unmetered some how, somewhere, some place. Just a few drip-drip-drips from the boosters or shooters will screw up everything.

Good Luck
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Old 12-16-2018, 02:04 PM
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Originally Posted by Japery View Post
I bought the 7lb summit racing fuel pump for a 350 CSB
5 lbs is fine. 6lbs is tops.
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Old 12-16-2018, 02:56 PM
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I agree...sounds like a carb issue. Need to fix that first. No way you should be fouling plugs.

That said...does it smoke? Can you post pics of plugs? Is there oil getting on them or just fuel fouled?

JIM
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Old 12-16-2018, 09:42 PM
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these are the hotter plugs. Autolite AR3910
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Old 12-16-2018, 09:53 PM
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I dont see any oil. some seem dry and others are wet with fuel. black smoke out of side pipes but not to bad
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Old 12-16-2018, 10:16 PM
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I agree, I tend to thing it's the carb leaking or just too rich.

I had an issue last summer with dire in the carb - kept the float from seating the valve and it dripped fuel into the carb...
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