zerMATT951

If you ran the elbow in until the threads were tight, but it didn't bottom out on the shoulder of the elbow, then your thread's are probably just fine. Put a nice thick layer of teflon on the elbow and try again. The most important thing there is to make sure the teflon is staying in place as you thread it in. The teflon will fill in the tiny gaps that can cause leaks. This is critical when you are threading a steel fitting into the aluminum head... the to metals will expand at different rates as they warm up, so you need something in the threads as a buffer to retain the seal.

Paulyy

Use some loctite.

http://www.loctiteusers.com/category/thread-sealing/