AFR Heads need longer screw in studs? One just broke.

[barronj]

Bought a set of AFR's from a member a while back, NIB, great purchase.

Just yesterday, I was tuning the carb & went out for a test drive when it starts backfiring through the carb, starts popping like crazy. Limp it back home, and pull the valve cover to discover a broken stud on the #4 exhaust.

It's a 351 block (never decked), trick flow pushrods (7.65), and the roller tip sweeps right through the middle of the valve stem, so I don't think it broke b/c my geometries are way off*.

A friend said he thought he remembered having to swap in longer screw in studs b/c the lock nut wasn't able to go down far enough on the threads for his peace of mind...

Did I just experience a weak stud, or is this something others have experienced?

[greenbullitt]

coil bind? improper adjustment? im pretty sure you know how to adjust valves though

[turbostang]

Assuming the geometry is in fact correct, and no other problems - I'd lean more towards overtightening the poly-lock. They take VERY little force to stay in place. Now, this is assuming that the breakage is in the threaded portion and in the area that the poly-lock sits.

If it's broken anywhere other than the threaded area, you have other MAJOR problems.

[mustgofaster]

There are a few guys on nloc.net that had the same problem. They wound up changing the studs.

[mustangguy289]

I had one break on me driving around town ... they were about 8 months old but not many miles. I replaced them all with ARP studs and have not had any problems since.