Header tubes are generally welded to the flanges on the motor side, then surface ground so the welds are what actually seal to the heads with the header gaskets. The few tack welds on the outside are most likely to hold the flange in the proper location while the tubes are positioned on a jig for proper angles.
That's what i was told by whoever makes Blackjack.
I bought a set back in the day of AK5000. They were tacked outside, but insides were a major fail. So many spots missed they leaked bad.
AK5000 were a stab at a coating, hot metal spray on them.
Only way to fix them was to weld all the flanges inside and machine flat. It would ruin the coating.
Sadly they did not care.
I have followed this thread glad to see you got the headers and thet look so nice. I have been screwed by.major companies so evey order no matter who you buy from.is a gamble now
