The Stovebolt Site Forums The Shop Area Engine Shop 292 Rocker Stud Replacement

I have a rocker arm stud pulling up. I believe you can buy threaded studs to replace the OEM pressed ones. Has anyone done this repair? Is it a DIY project or must I remove the head and take it to a machinist? Brian

There are two types of screw-in studs, the ones with a nut built in, and ones that just have a 7/16" thread on the cylinder head end, and a 3/8" thread for the rocker arm nut. If you use the type with the integral nut, the stud boss needs to be milled down about 1/4" or so before it's threaded. Either way, you're going to make a lot of shavings, so it's best to pull the head and have a machine shop do ther work. It's also very likely you'll tap the thread crooked unless the head is in a seat/guide machine, or at least a drill press while the threading is being done.

An alternative to threaded studs is to drive the press-fit stud back down to its normal height, and drill a 1/8" hole through the stud boss a little off-center, just barely putting a nick in thre side of the stud. Then drive a 1/8"X1" spring pin (roll pin) through the hole, locking the stud into place. If you're careful, and pack a rag around the stud boss, the drilling can be done without removing the head. Do a THOROUGH cleanup afterwards to keep cuttings from getting into the crankcase.

It's better to do any machining, drilling or tapping with the head off, though! You might get away with drilling and pinning one stud with a minimum of risk, though.
Jerry

Thank you Jerry. I believe I will go to the trouble of pulling the head and having a pro do it.

Follow-up question: do these press-ins pull out as a matter of age and normal wear, or should I be suspicious of other valve train problems causing this? At this time there is only one coming out. While the head is off is it worth getting all of them replaced with threaded studs?

In my experience, some studs do pull out just due to old age, and a slightly loose press fit from the factory. One thing that will start the process, on occasion, is a loose valve adjustment that allows the lifter to hammer on the valve stem. Something about the shock of taking up the looseness starts the stud moving.

Yes, by all means, get the machine shop to install thread-in studs on all the valves while they're in there. The most time-consuming part of the setup is getting the head aligned where all the stud bosses are pointing straight up. Once that's done, the drill/tap procedure goes pretty fast. You can find hundreds of sets of screw-in studs on Ebay. Just get a 3/8" set for a smallblock V-8, and you'll end up with 4 spares. The studs for the 6-cylinder are virtually identical to the V-8 type, and you won't have to pay the inflated prices just because it says "6-cylinder" on the package. Unless you're planning to go racing, get the type without the built-in nut, and all your machinist will have to do is pull the old studs and run a 7/16X14 tap into the holes. No milling! Use a drop of red LocTite on the studs as they're installed, and they'll stay there forever!
Jerry