Originally Posted by truckd
Just a question : why ? doesn't anyone use the grade 8 Allen bolts for the heads instead of ruining a socket or spending HRS. looking for a bolt with a small head, Allen bolt sockets are made for the bolts as well.
There various reasons for using studs and nuts rather than just bolts to secure cylinders and heads;
1. Studs can help align the cylinder and/or head with the engine cases or block (this can eliminate the need for cyl. and head alignment pins and/or dowels).
2. Studs are not as likely to be twisted when the nuts are torqued down in comparison with bolts. The result is that studs offer increased torque accuracy as well as the ability to maintain their torque settings.
3. Assembly is often easier with studs (many automotive engine builders use several long studs that are lightly threaded into the block to help with cylinder head installation (these studs are removed and replaced with head bolts after the cylinder is seated to the block.
Note: imo, none of this means that you can't effectively use high grade Allen bolts in place of the cylinder/head studs on these engines.