If you chase the threads use a "bottoming tap" to finish, it will make sure the threads are clean clear to the end of the cut, typically you have to use a standard tap first then he bottoming tap to finish.. Good luck..

 

It is a wall with threads in it, I don't think you need a bottoming tap for this. Obviously don't run the tap into the other side of the coolant passage.

Make sure you get a 3/8 straight thread tap, they are not standard tapered threads.

Personally, get it swapped to running AN fittings and goop em up

 

I’m leaning towards AN fittings because the heads are on and the motor is in the car. Would it be okay if I switched to the AN fittings with just less thread?

 

As so there is less to screw in and would tighten easier

 

Sorry to bring up an old thread. But I’ve had school and work. I really don’t want to take the heads back off, also I would rather not tap the hole with it bolted to the motor haha. So what if I just cut off a couple threads then deburred and sanded the bolt to mimic the factory ones just shorter.

 

Say what?

The bolts you are using now are longer than the OEM factory ones?

 

No they are factory bolts. But if they were less thread it would screw in tight. In theory haha