Stock Bolt

Can I use a slightly smaller head bolt head size than stock?

Puttin on new gaskets on a 1951 flathead engine. I have a set of headbolts (grade 8, 5/8 head). Should be ok to use a slgihtly smaller head than the stock grade 5 11/16 head right? Other than the size of the head, the bolt is the same dimension. Cast iron heads.

no you cant use a smaller bolt, there will be slop side to side up and down, just spend the money and get a set of bolts that are right

Ruger 77 22 .22 Long Rifle Bolt Action