Hello, I have a 66 F100 with the original 240, and about a week ago, I replaced the valve gasket cover, and after it was back together, the idle was a little off, but I didn't think much of it. Today, I realised I had no compression on cyl #3, so I took the valve cover off again, and the rocker arm stud had pulled out of the block about 1/4". My dad, a very experianced mechanic was with me, and had no idea how this could have happened.

It was lifting the rocker up too high, put with the help of a couple washers, its holding the rocker in the right place, and runs VERY nice now, but does anybody know how the stud could have pulled out? or even how to put it back it, my dad does not know, he said he has never had to deal with something like this before.

Thanks, Craig

 

I've sure been there & done that. About 20 years ago i bought my 1st Ford truck -68 F-100 240- with a very tired engine.

Put a short block in it & took the head to a machine shop for a valve job. Bolt it on & start to adjust the valves & one of the studs was spinning in the head. Urge to kill.

Yanked the head & back to the machine shop, guy tells me that Ford heats the heads & freeezes the studs, then the studs are pressed into the head. Tells me Ford got this brlliant idea from GM. That figures.

The guy taps threads in the stud hole & screws in a threaded stud. Much better.
Bolt the head back on & you guessed it another stud was spinning........

So if that stud continues to pull out, you'll need to install a threaded stud.

Good luck with it.

 

Since the studs are press-fit they can simply work loose over time. Ford makes replacement studs in 3 oversize steps, you just ream out the hole to the new spec and drive in the new stud. Going with screw-in studs is the real cure to this problem... but you're looking at $100 in machine work to get the head bored and tapped for the new studs. I'd just replace the one stud and keep an ear out for any others. Studs pulling loose isn't a very common issue unless you're using stiffer than stock springs with an aftermarket cam. Press fit studs are usually good to about 300lbs spring pressure, and at their peak open load the stockers are only ~170lbs.

Not a thing wrong with using hot/cold size differental to join metal parts... it's done in all sorts of industries. In fact, it allows you to make a much tighter, stronger connection than you ever could with a simple friction fit.

 

The stud should be repaired as it will most likely continue to pull itself out , and OH -- keep the RPM under 5000, another reason to pull studs, high rpm with all the weight of the long push rod and heavy lifter and weak valve springs ,might tend to float the valve until the spring compresses all the way and the only thing that will give is a loose stud or you will bend a pushrod.

stractor

 

Sorry bout being away for a few days, but very interesting info, I will talk to some machine shops and see what they charge, and also those replacement studs. Do you have a part number onhand? I try to keep her under 4000rpm, and only hit that once when me and my brother had a sound competition....my strait-piped against his c***y 350 with bottle.

I will check into this and then let you all know how it turns out, Thanks again.

 

Don't have any part numbers, but the studs come in oversizes of .006", .010", and .015". Should be able to get them at any ford dealership.

 

My 83 f150 with 4.9l has several rocker arm studs pulling out I bought a reman head from a guy at work that has the holes for the rocker arm studs threaded, thread size is 5/16 x 18, any recommendations on studs and rockers arms? The factory rocker arm stud size for the rocker arm nuts are 5/16 x 24

 

If you go with screw in studs, you'll be switching to having to adjust your rockers manually. They won't be the torque and go setup anymore. However, screw in studs are much stronger and won't pull out.
Personally, I would select the stud before having the holes threaded. You'll be very hard pressed to find aftermarket studs in the 5/16" range.

However, the stock rockers will fit on 3/8" studs. I had them on mine for a while until I switched to roller rockers.

Check out Summit Racing

https://www.summitracing.com/search/...rder=Ascending

You'll most likely need to get a 16 pack, since almost everyone orders for V8s. But, you'll probably still spend less than you would if you ordered them in singles. And you'll have 4 spares.
Then, have a shop modify your head for the screw in studs you pick, so that it matches the thread.

 

I did not hear of this option but you still need a machine shop to do the work I believe.
If you can get the stud back in and check the other have not pulled out some have them all drilled and pined.
The pin or the head boss would need to break for the studs to pull out again.

It may also be cheaper for the shop but you could still use all the parts you have now saving money.
Dave ----

 

More likely:
The stud will shear off where it was drilled because it created a stress riser there, at the max bending moment. Then you have a real headache.

 

Install screw-in studs.

 

And please go with the ARP studs. I once installed non ARP screw in studs and snapped at the end of the rocker studs. I almost sucked a valve because of it! When you buy the best, you can rest, without a mess.
Apply thread sealer to the threads in head.

 

Same here! I lucked out in that I was taking my rocker arms off to check something, and two of the studs were snapped in half. No idea how they were still working.
ARP all the way.