I am doing a 4.0 head conversion and my 1983 258 (4.2L) engine uses 7/16 inch bolts. The 4.0 head uses 1/2 inch bolts. Does anyone know where I can purchase 7/16 head bolts with sleeves to fit in 4.0 head conversion? Or do you know if the engine block can be machined to 1/2 inch holes while the engine is still in the Jeep?

The 7/16 head bolts you have will work just fine. You don't need to do any drilling on the block either. You have several options. I used a head made for 1/2" head bolts with 7/16 bolts for years and never had a problem. I didn't realise the discrepancy until I did my 4.0 head swap. What I did then was buy a set of spacers from Mustang Warehouse because they had the best price I could find at the time. If I were doing it again, I would get just 4 spacers from Summit Racing and saved some money. That is all you need. Two would be enbough to position the head, once it's torqued down it's not going anywhere. You could even use some tape on a couple of bolts instead. Like I said, I used nothing before and had no problems, maybe I'm just lucky though. <img src="/forums/images/graemlins/cheers.gif" alt="" />