Head stud diameter

[35 coupe]

Wondering if any one ever miked the outside diameter of old original head stud ( block end thread) compared to a new stud, and should there be a difference. Is there a difference between cut threads and rolled threads, diameter difference. Thanks

 

[BillM]

The diameter of threads is the "class"; common bolts are Class 2. Studs are usually Class 3 which is a tighter fit; or sometimes a Class 5 which is an interference fit. The end of the stud that screws into the block is referred to as the tap end. See the links below to find the diameter specs for the different classes. Cut or rolled still need to fit the diameters for whatever class they fit into.

Ref: http://www.texthreadinc.com/studs.html
Ref: http://www.engineersedge.com/screw_threads_chart.htm

 

[36tbird]

Don't know the reason for your question but maybe you are thinking like me that keeping the studs or bolts true in the head holes, it might help in preventing electrolysis and ease head removal. My thinking about this lead me to using step washers on the heads to do this. You can get them from this place, www.stefs.com/bandb/products/productpages/washerstep.htm. You need a special drill to install them but it is an easy procedure. I'm using them on my 8BA, newly rebuilt. Have not had occasion to pull the heads to test my theory.

 

[Ol' Ron]

BillM Thanks, great information. I like your distributor cap modifications. This should help . Have you had any luck modifying the advance curve in these distributors?

 

[BillM]

Ron thanks for the comment; I haven't done any mods to the advance in the distributor. Have thought about it but don't have any access to a distributor machine. Keep thinking about how to make something to take its place but haven't done anything about it yet. Maybe someday.