Which tap size to chase the threads in the valve cover bolt holes?

Which tap size to chase the threads in the valve cover bolt holes?

I've got a 92 4.0 liter, and several of the valve cover bolt holes are fouled in shreds of hardened RTV. As a result the bolts are binding before they seat.

1/4"-20.

If all you can get locally are taps, take a bolt in that size, and cut two or three longsize grooves in it, so you can use it as a thread chaser. Why? Because using a tap, if you're not careful, will result in ruining the hole.

Using the "slotted" bolt lessens, if not eliminates, that risk. Make sure you back it out to clean out the slots/flutes, either way. If you can, it's best to find a "thread chaser" - which is designed to clean out the threads and reform them if they're a little "off" - but the bolt is second best and works well.

5-90

5-90- Thanks for your expertise.

In my professional work I deal with military specs and produce instructional graphics, and often find important specs missing from the "official" literature.

Like the incomplete military documents I have to rifle through, this kind of spec isn't in the Jeep FSM.

Wasn't looking forward to counting bolt threads per inch.

You're the man!

Thanks for the bolt trick Jon (5-90). I had a problem with 2 bolts on my D44 cover. Was going to get a tap, but I'm glad I didn't. While the 2 bolts don't turn in by finger, they will go all the way in with anti seize. Thanks again Amigo.

92DripCherokee said:

5-90- Thanks for your expertise.

In my professional work I deal with military specs and produce instructional graphics, and often find important specs missing from the "official" literature.

Like the incomplete military documents I have to rifle through, this kind of spec isn't in the Jeep FSM.

Wasn't looking forward to counting bolt threads per inch.

You're the man!

Click to expand...

Which will probably be the focus of a future book - tips & tricks for mechanics and hobbyists...

I know what you mean on MILspecs and instructional graphics!

For screw sizes, check the Tech section of my site (www.kelleyswip.com/tech.html,) and do please feel free to pass along anything you may have to contribute that I don't have up there!