I have a 350 chev in my 58 Apache and it bent a push rod on the week end so I took the rocker of pulled the push rod out and noticed a groove in the stud that the rocker pivits on it look like the rocker has wearn the groove . I think the stud could be bent and that is why the rocker has wearn a groove in the stud ? Next question it is a stranded head (cast iron ) do the studs screw out or are they pressed in ?
most castings are press in studs, there are a few hi performance castings with threaded studs, but commonly they are pressed if they are 3/8 not 7/16 ect, hope this helps!
I had a Mustang 289 that had the same problem many years ago...the pushrod goes through the head in a machined slot and that is what keeps the pushrod and rocker arm straight...sometimes that slot gets worn or maybe the pushrod was worn allowing the rocker to tip over...you can pull out that stud and replace it...its as simple as stacking washers underneath the nut and turning it until the studs come out. I dont think there was a fancy way to put the new one in...maybe someone makes a tool or something...but I think if the slot in the head that locates the pushrod is worn..you will have the same problem again. Look at the tip of the valve too...if that stud is worn that much the valve tip is probably screwed up...good luck...
First, what bent the pushrod? The rocker stud damage could have been as a result of the pushrod loading the rocker sideways. Anyway, once we determine why it bent[over reving, hit piston due to too little clearance], most studs are pressed in. As the post above says, put a nut on it with washers or a spacer under, and pull it out. I always replace with a screw in stud. Fairly easy to do, tap it, and use thread sealer on stud.Put a new rocker and pivot ball on also. While the motors opened up, pull the rest of the pushrods to check.Push rods dont bend by themselves.
I had the problem with the worn pushrod slot on a 350. The only solution to the worn hole was to pull the head and replace the press in studs with screw in as well as a guide plate to keep the pushrods straight.
Pushrod could have been bent as a result of the groove in the stud finally wearing to the point to where the rockerarm got cocked to one side far enough to get things in a real bind. Replacing the pressed in stud, rockerarm, and pushrod may be all thats necessary. Good time to check the rest of the studs while your at it. Another stud can be pressed (hammered) in without taking the head off. Machining for screw in studs or pinning pressed in studs will require removing the head but just replacing the pressed in one can get you by and in some cases will last as long as the original especially if some thread locker is used.
The valve was probably loose and that allowed enough monkey motion for the push rod to get in a bind, either that or any of the aforementioned scenarios. I have seen this before. And once the stud was even bent (the slot in the side had weakened it). I heated it and straighted it and told the guy to sell the truck. But he didn't and we were back in there! I actually removed the head and sent it to the machine shop.Replacing the press-in stud is a scary proposition to me, because of the chance of cracking the boss. But the dirt track guys have the answer. There is a "cheater" threaded stud you can use. One reason I mention this is the screw in studs that GM used requires machining the boss down since the stud has a hex for tightening and it would obviously be in the way of the rocker arm. The cheater studs don't have this (they look just like a pressed stud once installed) and can be done with the motor in the car, as long as you are careful about the shavings from the tap. Hope this helps.
Put the new press in stud in the freezer for a couple of days then quickly & gently tap it in, might work might not but worth a try This has worked for me putting sleeves in tractor engines
As above; PLUS, where the rocker wore the groove in the stud, it may break at that point when you try to pull it out using the stacked washer/nut method. I've heard of guys cutting the stud off level with the boss if that happens, and driving the part left in the head into the water jacket. Studs do come in oversizes, but you probably don't need that as it did'nt pull out, as they often do. There is also a tool used to drive in a stud so as not to damage the threads, you may be able to rent/borrow one of those; in a pinch, use a brass hammer and several nuts (regular nuts) interlocked together. Be sure the valve tip is in good shape before doing anything, things do tend to wear together. You may be able to use a self aligning rocker, to help keep things centered, if that's the case. Butch/56sedandelivery.
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