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Spark plugs
Waco Cobra Club,
We are trying to figured out what type of spark plug to use in one of our Cobra's, this car has a 351W engine with Aluminum World heads that were installed on the car about six weeks ago, some of the plugs look as if they are firing good [white chalk look] but 3 plugs are black as if the plugs were not firing. We are trying to figure out if the val's need adjusted, are could it be the plugs, we're using AutoLite 25's at this time. At the time when the heads were changed we had energizer rocker arm installed but didn't change the push rod, we would like to go to a better push rod. Three questions, any recommendation are comments: What about the plugs, do we need to take a look at the Val's, an about the push rods???we are thinking about comp cam 4130. If anyone can help we would sure appreciate it. tfxace@aol.com papaj234@aol.com :confused: |
Change of heat range is addressing the "symptoms" not the cause, as MOST plugs are firing correctly. Only a few cylinders are affected, not all. I would have to assume the plug wires are same for all cylinders and in good shape. A weak spark to these cylinders would result in your description, hmmmm,,,not likely that, but don't over rule weak spark to affected cylinders (wires, short in cap etc.).
Incomplete combustion,,,,hmmmm....valves set to tight, loss of compression could cause that. Ruling out other factors like, piston rings etc. must be the top end (carb, intake, valves). Easy enough to move "rich" plugs to "clean" holes. Clean plugs should "foul" just like old plugs did, and "old" plugs should "clean up" in the good cylinder. This would verify that the "bad" plugs are NOT the problem (only a symptom). Possibly running rich ONLY to affected cylinders, doubt it. Sure sounds like a valve lash problem. Good luck, I'm drained! Ernie |
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