Should I chase the head-bolt threads when re-installing a head? And if so, what tool do I use? I have found taps. I have heard from good authority that chasing threads is different than using a tap. Please advise. Thank you.

 

Always.

ARP Thread Cleaning Chasers - Free Shipping on All Orders @ JEGS

 

The main difference between a chasing tap and a thread tap is the taper at the end of the tap and the need when threading to keep the tap aligned to the hole. A chasing tap is flat at the end.

BTW, as a mechanic I've done several head replacements over time on cast iron and aluminum block engines and have never chased head bold holes unless they don't thread the bolt smoothly or show to be crudded up. IMHO, blow the holes out with compressed air and thread a bolt into the hole, if it threads smoothly to the bottom it should be fine without chasing the hole when properly installed. I've never had a problem with any head gasket that I've done.

 

Best practice is to always clean and chase holes before installing any bolt. Obviously no one does that for EVERY bolt, but for your mains, rods, heads, and cam caps, I definitely would. It's extremely easy, too. Spray some brake cleaner in the hole, spray some compressed air in the hole to dry it out, chase it, done.

 

Thank you both. I've blown compressed air several times and the threads still look cruddy to me.

 

Thanks NotARacist! Just talked myself into buying an ARP thread chaser from your URL above. Thanks again!

 

Got the ARP thread chaser. Chased all ten head-bolt threads. Two were tricky. Several were sticky but none extracted much in the way of debris. I should have the head on tonight or tomorrow. Thank you all.