Bad valve cover thread
 

I have a new set of Dart Iron Eagles and it turns out that one thread for the valve cover bolts is bad. I tried to rethread with a tap but their is something in their that keeps breaking the teeth off the tap when trying to rethread. Its like a piece of sand or something when it was manufactured. So I gave up trying to retap. What are my options besides taking the head off and taking it back to the machine shop for a replacement?

Grip,

It almost sounds like maybe a tap was broken off in it at the factory ? Get a small drill bit, 1/8" should do and see if you can drill the hole a little deeper. Just be careful so that you dont break the drill off too. If so, it is probably ok and you could put a helicoil in it. There is not much room around the hole, but it can be done. If there is a tap or drill broken off in the hole, you will have to find a shop that has an EDM machine to "blast" the broken tap or drill out first :(

By the way, are you using a good quality tap ? There is a big difference in them. I have found the SnapOn ones the most reliable and strongest as far as not breaking.

Bill Koustenis
Advanced AUtomotive Machine
Waldorf Md

I used Craftsman. Should I try a Snap on?

Grip,

Its worth a try if you are breaking the Sears taps. Also, are you using any type of cutting fluid .... that will help tremendously. Go real slow, a turn or so at a time, take the tap out and flush the hole out with brake cleaner, then more tapping fluid and go a little further. Also, the holes are usually not that deep, so you may need a bottoming tap too.

And ... there could very well be something stuck in the threads causing the problem. Hard to tell without being there.

Bill