Some people will say a Spark plug worked for them and I have personally seen a few cars where the owners plugged the holes with a sparkplug but I have plugged 2 separate sets of heads on 302s with E7TE heads and they took 2 9/16 Coarse thread bolts about 3/4" long..In both of the cars/motors I have plugged, a 5/8 Tap would slide through the holes in the heads loosely...The Reason I think some people use a 5/8" spark plug to plug up the holes are because there is SO much Carbon buildup in those thermactor Ports, that the Threads just make threads in the Carbon and not the heads...
well, Im glad the 5/8 x 11 worked for your heads but for the 2 sets I Plugged a 5/8 was too small and just loosely Slid in the hole ..Maybe on yours it was a 5/8 x 11, but on the 2 I have plugged it was 9/16 coarse thread so dont tell me to try again..
9/16 worked for me too. 5/8 is too large and won't even start. Just to help out 5/8 is larger than 9/16. At least now we know there are 2 sizes and now they can be posted before anyone goes to the parts store.
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