hello- i just bought some used dart heads. the guy had them on a 400 in a nova and they look new so they're mine now.when i got home i started going over them again and discovered 3 of the steam holes don't go all the way thru. i try and can't get them with a drill so itake them to a machinist and he tells me there are broken drill bit pieces in there!he says that they regularly get plugged and they aren't that important. how would you feel about running these? i would have at least 1 hole open on each cylinder.

 

I would go ahead and drill them. They don't have to be perfectly perpendicular to the head, so just drill them at an angle; feel inside there, and find where the water jacket is, and aim for it. It's not rocket science.

Here's a set of Dart heads that I drilled steam holes in. The ones that are circled are actually at about a 45° angle toward the exhaust port side of the casting. In these particular heads if you try to drill the ones on the intake side straight into the block, you'll never hit water at all, you'll be inside the head bolt boss. That's probably what happened to your heads.... Stimpy left his mark.

 

i can stick a wire thru the steem holes and see it in the water jacket. what i'm worried about is that on 3 cylinders i'll only have 1 steam hole. the machinist tells me they regularly get plugged with junk in the water any how. do you think they'll run hot?

 

I wouldn't put them on there being plugged. Fix it right and have the peace of mind. Don't trust the machinist.