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Old 07-16-2012, 10:07 AM
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350 sbc fouled spark plugs

Hi my 350 sbc seems to keep fouling the 2 front spark plugs on the driver's side of the engine. I replaced all plugs about 600 miles ago, and the other day on the highway it starts to pop and backfire out exhuast. Got home and removed al plugs to check, the 2 mentioned were covered in a black tar looking substance, which i managed to clean off with a wire pad, for the time being. The other plugs all ok. The engine has a brand new edelbrock 600 performer carb and edelbrock rpm air gap intake. Other then that engine is bone stock. Being that its only these 2 plugs fouled i dont think its a fuel problem, maybe oil getting into these 2 cylinders? I've heard that it could be worn valve guide or seal, intake gasket, or piston rings (doubtful about rings though as it is only 2 cyl that are bad). Is there anyway i can go about checking before i go ahead and replaced intake gaskets?? Should i pull valve covers first??

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Old 07-16-2012, 10:10 AM
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I had this same problem at one time. What your finding on the plugs is oil.
You said you added the intake and carb, was it recent? If so I suspect the intake gaskets did not seal. Sometimes you can pull the carb and if you find oil in the plenum then it's got a leak. Also in many cases guys will buy a new intake and they always seem to want to use fel pro gaskets. Certain fel pro gaskets are not for use with aluminum intakes and will not seal up. I always use the cheap paper hanging off the shelf Mr. Gasket jobs.
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Old 07-16-2012, 10:19 AM
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Originally Posted by grandslam1991 View Post
Hi my 350 sbc seems to keep fouling the 2 front spark plugs on the driver's side of the engine. I replaced all plugs about 600 miles ago, and the other day on the highway it starts to pop and backfire out exhuast. Got home and removed al plugs to check, the 2 mentioned were covered in a black tar looking substance, which i managed to clean off with a wire pad, for the time being. The other plugs all ok. The engine has a brand new edelbrock 600 performer carb and edelbrock rpm air gap intake. Other then that engine is bone stock. Being that its only these 2 plugs fouled i dont think its a fuel problem, maybe oil getting into these 2 cylinders? I've heard that it could be worn valve guide or seal, intake gasket, or piston rings (doubtful about rings though as it is only 2 cyl that are bad). Is there anyway i can go about checking before i go ahead and replaced intake gaskets?? Should i pull valve covers first??
If this is a a 1970's early 1980's model you can add wiped cam lobes to you list.

Bogie
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Old 07-16-2012, 11:29 AM
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Yes the intake installed about 2000 miles ago, and i believe i bought fel pro gaskets and had my mechanic the intake. Maybe ill replaced those gaskets and see if it helps.
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Old 07-16-2012, 01:36 PM
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Originally Posted by grandslam1991 View Post
Yes the intake installed about 2000 miles ago, and i believe i bought fel pro gaskets and had my mechanic the intake. Maybe ill replaced those gaskets and see if it helps.
While I do suspect the intake gaskets, I start with pulling the rocker cover and check the valve motion first as this is easier than getting the intake off and allows ruling the cam lobes in or out as a problem with a minimum of effort before pulling the intake.

Bogie
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Old 07-16-2012, 01:55 PM
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Ill definitely pull the valve cover to check the cam first, hate to do work that doesnt need to be done, thanks bogie.
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Old 07-16-2012, 03:40 PM
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Originally Posted by grandslam1991 View Post
Ill definitely pull the valve cover to check the cam first, hate to do work that doesnt need to be done, thanks bogie.
Have you retightened the intake bolts? It often takes three or four times retightening before they take a set and hold torque.

Not saying to over tighten them, just start from the inside and work towards the ends, swapping sides as you go. If the gaskets haven't degraded totally, they still might seal. Might.

If you end up replacing the intake gaskets, be sure to retighten after a couple heat cycles. Repeat until the bolts are staying tight.
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