Thread: 351W rocker studs

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I know zip about fords so bear with me...

Friend has a 68 mustang w/351windsor (not original) and unknown heads. Anyhow, a rocker stud broke on the #8 cylinder (second rocker from the rear) and I am wondering if they (studs) are pressed in or threaded. I am guessing they are pressed because there is no "nut" just a straight shaft.

They are non-adjustable, "rail" type (correct term?) cast rockers. So, should we pull the head and bring it to a shop or can the stud be changed in the car?

Let me know if more info is required.

Originally Posted by 65cayne

I know zip about fords so bear with me...

Friend has a 68 mustang w/351windsor (not original) and unknown heads. Anyhow, a rocker stud broke on the #8 cylinder (second rocker from the rear) and I am wondering if they (studs) are pressed in or threaded. I am guessing they are pressed because there is no "nut" just a straight shaft.

They are non-adjustable, "rail" type (correct term?) cast rockers. So, should we pull the head and bring it to a shop or can the stud be changed in the car?

Let me know if more info is required.

They are pressed in place - and now is the time to change them ALL out to screw in type. It's a fairly simple job - you pull the old press in style - you can use a stack of washers and 3/8" NF nuts and work them out. You then tap the holes with 7/16"-14 taps, starting with a taper tap then to a plug tap then a bottoming tap. Since it's cast iron, you will need some cutting oil on the taps. Then install a set of studs - Summit lists dozens( Trick Flow Specialties TFS-51400613). You'll need a 7/16-14 into the head and a 3/8-24 for the rocker itself. It's also a good time for a valve job

Thanks for the quick reply.

does that then necessitate the purchase of new rockers and new pushrods?

I dont think he is going to want to rebuild the heads because the motor is fairly new and it ran great up until the failure. He is also squeezed for cash and I (his main helper) am squeezed for time although you make that sound pretty easy. Any idea what it might run to have a machine shop replace the one stud versus replacing them all with adjustable type studs?

Depends on how much stud is still sticking up out of the head. If there's enough to get hold of, or to weld a nut on to, you can probably do the job without pulling the head. If not, well, them's the breaks, bite the bullet and tear her down.

Originally Posted by R Pope

Depends on how much stud is still sticking up out of the head. If there's enough to get hold of, or to weld a nut on to, you can probably do the job without pulling the head. If not, well, them's the breaks, bite the bullet and tear her down.

It broke just under the nut, so there are a few threads there still...

Originally Posted by 65cayne

Thanks for the quick reply.

does that then necessitate the purchase of new rockers and new pushrods?

I dont think he is going to want to rebuild the heads because the motor is fairly new and it ran great up until the failure. He is also squeezed for cash and I (his main helper) am squeezed for time although you make that sound pretty easy. Any idea what it might run to have a machine shop replace the one stud versus replacing them all with adjustable type studs?

You can use the same rockers and push rods.

By the time you pull the head to take to a machine shop, you have a fair amount of time and money spent. The machine shop will have to either drill or (hopefully) EDM the failed stud out. That takes care of one fatigued stud - but there is the potential of 15 more following. Studs are not one of those items that ever get replaced until someone wants to either build a performance engine or one breaks. If he has an aftermarket performance cam, it is even more important to change these studs. Once the heads are off, the job is easy - with removing the broken piece being the hardest part. Pull the rockers off the existing studs, keeping them in the same order as removed for later reassembly, the valves can stay in-place. Take the heads to a machine shop, and have them tap the holes for the screw ins - the hole is the correct size for 7/16-14. Bring the heads home, screw in the studs with some LockTite, and put the engine back together. Two days - your time, 1 day a machine shop time is a reasonable, unhurried schedule to work towards - faster by abouy 50% if you're in a real rush. Parts costs - ~$125(studs and a GOOD Fel-Pro valve grind gasket set), machine shop - who knows??

Dave, Pope,

thanks for the information. I think I will recommend 16 new adjustable studs to him. We'll pull it apart, I'll show him how to remove the studs and leave him to the task. Then, I'll leave it to him if he wants to buy the taps or have a machinist do it.

You say we can re-use the rockers...do I re-use the hardware? There was (as I recall) the rocker, pivot ball, and a spacer (like a thick washer)...all of that goes back on with new jam nuts? Do you think new studs will upset the rocker geometry or will that be minimal?

Never have done a conversion like this before so I am learning here as well...

Originally Posted by 65cayne

Dave, Pope,

thanks for the information. I think I will recommend 16 new adjustable studs to him. We'll pull it apart, I'll show him how to remove the studs and leave him to the task. Then, I'll leave it to him if he wants to buy the taps or have a machinist do it.

You say we can re-use the rockers...do I re-use the hardware? There was (as I recall) the rocker, pivot ball, and a spacer (like a thick washer)...all of that goes back on with new jam nuts? Do you think new studs will upset the rocker geometry or will that be minimal?

Never have done a conversion like this before so I am learning here as well...

As long as you use the 3/8" top with the 7/16" bottom, everything is reuseable 'as is' with of course, the new nuts. You haven't changed a thing but the fact that you screw in the stud rather then press it in to place. The geometry remains exactly the same - that is unless you go to roller rockers. Then you might have to change the pushrods. The only thing you might have to be careful of is if you get a set of studs that have some more thread then the OEM's, then you have to adjust them rather then run the nuts down until the bottom. Let's cross that bridge if you come to it later. If there are other performance goodies built into the engine, now is the time to invest in roller rockers

Just a bit of eye candy on a later 5.0 SBF engine:

The best way to extract the broken stud is to but a 7/16 nut over the broken stud,weld the nut to the to the top of the stud let it cool then weld a bolt to the the nut head down . use a steal plate drill Three holes into the plate that that will Aline with the two adjacent studs to the broken one .I install a1' piece of pipe over both the adjacent studs with a washer and a nut on each stud. Bolt the two end nuts down solid Then install a nut on the nut that has to be pulled and tighten it until the stud pulls .this can be doe on the car . I did this on the side of the road with a acetylene torch to pull the stud on my pickup.

I guess I forgot to follow up on this one. I dont have a welder either but thanks for the suggestion.
The owner opted to just have the one stud replaced at a machine shop. We reinstalled the head, adjusted the rockers, and moved on. We are currently working some wiring issues.

Finally got the engine and wiring back together. Tried to fire it, no power to the coil. Everything looked okay (I thought) prior to putting the juice to it. So I look at the diagram and run a jumper from the +coil to the "I" terminal on the fender mounted solenoid. The engine fires right up.

Head lights on, engine warms up and starts smoking from the PS exhaust manifold. Burning off residual oil I assume but we will shut it down to make sure...turn off key, remove key, engine still purring away. BTW the valve train sounds great, engine sounds great, etc...I yank of the coil wire and kill the motor while we assess what just happened.

Fire it up again and pull it in the garage for the night (getting late anyway) and this time the engine dies when the key is off. What's different? We did not have the headlights on....start engine, turn on headlights, key will not work. Turn off head lights, then turn off key, engine dies. It will start without the headlights on (lights not feeding coil).

So, still a glitch in the wiring somewheres. The harness on both sides of the firewall has been badly "cobbed" up so no telling what the problem is. That's all for now.

Originally Posted by 65cayne

Finally got the engine and wiring back together. Tried to fire it, no power to the coil. Everything looked okay (I thought) prior to putting the juice to it. So I look at the diagram and run a jumper from the +coil to the "I" terminal on the fender mounted solenoid. The engine fires right up.

Head lights on, engine warms up and starts smoking from the PS exhaust manifold. Burning off residual oil I assume but we will shut it down to make sure...turn off key, remove key, engine still purring away. BTW the valve train sounds great, engine sounds great, etc...I yank of the coil wire and kill the motor while we assess what just happened.

Fire it up again and pull it in the garage for the night (getting late anyway) and this time the engine dies when the key is off. What's different? We did not have the headlights on....start engine, turn on headlights, key will not work. Turn off head lights, then turn off key, engine dies. It will start without the headlights on (lights not feeding coil).

So, still a glitch in the wiring somewheres. The harness on both sides of the firewall has been badly "cobbed" up so no telling what the problem is. That's all for now.

It sounds like your engine is grounding through the headlights . When you turn them on you loose the ground because there is power comming through the wire . Make sure you have a good ground and see if it cures the problem.