NGK B6L is the usual number, Dale. Don't know that it directly cross-references to the H10. NGK is backwards on heat - B5L will be hotter.... I've found NGKs somewhat more challenging to find...Autolites work well for me.
The fouling is very likely to turn out to be an issue separate from the plugs entirely. Oil, fuel are always suspects, misfire or retarded curve can also do the job.
Talked with Red's Headers about spark plug recommendation when I ordered the new Edelbrock Block letter heads last week and Jim recommended the NGK FR4GP. It's a platinum plug. Has anybody any experience with it?
Just building an engine with those heads - will update the HAMB once we fire it (don't know which plugs we'll use as of yet). Just to everybody knows, the new block letter heads have a re-tooled plug area - they use a long reach plug, not a H-10 style. So - plugs that fit these new heads are NOT the same plugs you can use on your traditional heads or older/original Edelbrocks.
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