I am installing a used head on a used block where both were ordered from eBay. I cleaned out the threads with compressed air, brakeclean, and a diy thread chaser I made with an angle grinder and old head bolt. However, even after all that cleaning the threads, all of the head bolts do not thread in by hand smoothly. This isn't a problem with the new head bolts because old ones do the same. For some reason the bolts went in easy without the head in place. I put my old broken head on my old broken block, and head bolts went in by hand and were smooth as butter.
Is this ok, or will tightening to full torque rip the threads out of the block? How can I fix this?


The bolts had resistance and did not go in all the way when tightening by hand with this


If I held a ratchet like this (note that it is not that much leverage) I could feel some resistance, but the bolts went in smoothly.

 

A bolt as in the first image explains why won't go in smoothly. Something damaged it. A shifted head gasket can pose some friction but not as much as that bolt would.

 

That bolt is the thread chaser I made by cutting groves in it with an angle grinder. All the bolts are fine. I also oiled the head bolts before I put them in and wiped them so there was not too much oil.

 

I'm going with Externet, your DIY thread chaser looks suspect to me. Will it thread "smooth as butter" into the old head that the other bolt go in smoothly? If not, that answers your question. That would say that you have deformed the threads in the new block. I didn't say ruined, BTW. Probably recoverable if that's the deal.

 

I ended up putting the head bolts in and they torqued up pretty smoothly. I don’t think the thread chaser would be a problem because it went in the old block fine and had less resistance than the new head bolts that I tested before putting the thread chaser in. The thread chaser also got some dirt out of the holes.