I did the initial startup of my 70 351C. Fired and ran great within a few seconds of the turn of the key. Then things went down hill. I noticed leaking around the spark plugs. Upon inspection the heads have a flat land at the plug thread and the plugs installed are beveled without a compression seal. Obviously not compatible. Unfortunately 4 parts stores all call out the plug which is obviously wrong... Any help or numbers for the right plugs?
Sorry but I can't help you there. I have never seen a 351 Cleveland that didn't have tapered seat spark plugs. Maybe you can use something to measure the thread length and depth, then look in the parts book to find some plug with a similar heat range.
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David Shelton
Lone Star Gashole!
If you can get a physical description of the hole, like thread diameter, hex and reach (you already know it's a gasket seat), you can find it in this chart and cross it to whatever brand you like.
351C Spark Plugs
Linear Mode
