I'm ready to install heads on my car, but need to chase the head bolt hole threads first. I have a 7/16-14 tap, but don't want to leave metal shavings in the water passages, that probably wouldn't do the water pump much good. I'll vaccum the holes out after I chase them, but is there a better way to do this? I already have the tap, and prefer not to wait on a thread chaser if I can do the job right with a tap. The threads are fine, I just want to remove the sealant in the holes.

Thanks!

 

A chaser is really best, because it does not attempt to cut any new threads. A tap may cause some metal shavings, but a chaser is just going to clean any residue off the threads. As far as keeping any gunk from getting into the passages, that might be a little tough. You could always do a flush after you get through.

 

place shop vac next to the tap when using it

 

OK...any idea where I might find a chaser without ordering it online? I don't remember ever seeing them in any hardware stores or at Sears. I'd prefer not to wait on it, I'd like to do it tomorrow if possible.

I'm not too worried about leaving a little thread sealant in the holes, its the metal shavings that a tap would leave that bothers me.

 

You should not use a tap to chase threads. The tap will actually cut metal out of the old thread pattern, while the chaser burnishes the threads (actually pushes the metal back into its original shape). The same goes for using a die nut thread chaser instead of an ordinary die for external threads. Recutting the threads with a tap or die will slightly reduce the metal to metal contact area of the thread engagement and weaken the tensile strength of the fit.

You should be able to buy individual thread chasers from any tool supply store, Snap-on, MAC tools, etc. I bought a complete set (Metric, SAE NC, SAE NF) from Sears for around $50. It was a good investment, as I use it quite often, not only for head bolts.