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#1 |
Registered User
Join Date: Feb 2006
Location: Roseville, CA
Posts: 5
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Odd spark plug wear
I am hoping some of you have seen this kind of pattern before and can explain to me where I should be looking for a cause. This is a 350 TBI motor that has gradually started to get intermittent misses, getting worse over time. I pulled the plugs and all 8 of them have a dark gray spot going down the insulator, some with deposits on the spot also. I have attached a couple photos to show what I am trying to describe. These plugs have almost exactly 10,000 miles on them. Thanks for any help.
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#2 |
Registered User
Join Date: Feb 2004
Location: Albany, NY
Posts: 522
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Re: Odd spark plug wear
increase the carburetor jet size slightly, take out some timing, or go to a colder plug.
from: http://www.dragstuff.com/techarticle...ark-plugs.html
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RN U OVR |
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#3 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: Odd spark plug wear
TBI motors dont commonly have carbs
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#4 |
ASE master tech/machinist
Join Date: May 2008
Location: Blue Mound Texas
Posts: 303
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Re: Odd spark plug wear
Go to a colder plug, CR43TS ac delco is the factory plug for TBI trucks, as stated above by senator back some timing out of it. On a TBI motor you have to unplug the "timing control module" which looks like a breaker, that is what controls the advance instead of a vac advance. Dead nuts zero timing is "ideal" per GM, but any place between 0 degrees, and 6 degrees after will work. Also make sure there is no exhaust leaks, with plugs like that a burnt valve is a possibilty. The deposits are cause by the wet fuel that lingers around the exh valve in the chamber. If you can burn that fuel, your problem will burn with it.
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