Six heat exchangers leaking under gasket. Options

[914itis]

I installed the heat exchangers with all new gasket and they were leaking . I removed them to adjust and the gaskets are not usable. I had to order new gaskets.
Are there any tricks to the trade ?

The headers that I removed had no leaks .

These are six HE's. Not the four.

[rgalla9146]

Hey Paul
Are the 6 flanges thicker or thinner than those on the headers ?
Be sure that the threads on your exhaust studs have been cleaned with a die.
A good parts store will have repair dies that are the size of a 13 mm nut.
The barrel nuts can tighten on the threads before tightening the flange to the heads.
Also, as the barrel nut goes further onto the stud, the allen key can be pushed out of its recess before the nut has tightened the flange to the head.
You can remedy this by putting a split lock washer under the barrel nut.
You can determine which cylinder is leaking by removing the spark plug wires one at a time while the engine is idling.
Use insulated spark plug pliers.