Rocker stud got loose, again

please bare with me as I am trying to learn a little.

is it the "F" thread that is loosing up from the head?
Is it possible the length "C" is too long and getting binding from bottoming out before torquing out on shoulder face?
Is there a relief so the last thread does not hold off the shoulder face?
Is the practice to use a torque wrench to provide final pull down?

It's the thread marked "F". No it doesn't bottoming. Yes it's torqued with a tourqe wrench. It seems that the rocker nut and polly lock was still tourqed, the rocker can't turn around on it's own stud...
...Very strange

quote:

Originally posted by SF:...can't turn around on it's own stud...
...Very strange

thats why it seems to me you torqued out before the shoulder face touched and the "torque" should have been to force side the shoulder face and put stretch on the "F" section

Is it possible to run the studs in by finger and use prussian blue to see if there is contact and the % quality on the shoulder face?

working with bolted surfaces that required metal/metal contact, I have seen where a cone of metal was pulled around the threaded hole causing an improper torquing.

Mayby I got that wrong. The bolt "F" does not hit the head in the threaded hole, it is not to long. the stud is bolted down to the push rod guide plate.

Hello,
Try loctite 271, this will keep the stud from loosening. it must be clean and dry on both parts, carb cleaner and compressed air to blow out the head hole, use a rag around the nozzle so you don't get blow back,!

I assume your torquing it to some spec called out by ???????.
and the stud is shouldering on the C/B shoulder of the stud at the hex.

You will probably have to do all 16, I did this on my build.
Good luck,
Mark

the "stacking" of surface areas that could possibly not be 100% metal to metal increased with the plate.
I wonder if putting an acorn nut on the end and tapping with a hammer while torquing would help ensure the surfaces go metal to metal and the thread section "F" is stretched with torquing.

I would think a loose stud indicates something is stretching. Like the threads in the boss that the stud is screwed into.

You may need to pin them in place but that will only work if they are unthreading themselves.

If the studs are pulling out, you need to use steel thread inserts to repair the casting.

The heads are equipped with insert threads, helicoil.
I have to go through them all. Maybe I go for shaft mounted rockers and skip the guideplates, one problem less, I hope...

quote:

Originally posted by SF:
The heads are equipped with insert threads, helicoil.
I have to go through them all. Maybe I go for shaft mounted rockers and skip the guideplates, one problem less, I hope...

Yes, that would be an alternative and maybe a necessary one considering the issues you are having in the valve train?

It certainly would reduce as much as possible the emotional stress you are suffering now.

It is a pretty expensive solution though.

Anders,

I noticed on one of your posts elsewhere this was a Fontana block.

For an alloy block and solid cam, one other thought would be your lash setting. Are you setting lash hot or cold and how much? If you are setting it hot and fairly tight, the growth in aluminum block/head pushrod engine can result very low lash at cold. That would certainly pose the potential to create such a problem. For a couple hundred degrees F temperature difference the change can be as much as .015”. Alloy engines can loosen up quite a bit as they warm up but with that kind of growth potential it’s easy to understand why they can tend to be set up in a manner that would make them very tight cold. Always advisable to be gentle with such engines on start up until they are brought to full temperature. Many similar race engines have preheating systems to help with such issues.



Best,
K

Kelly,
The lash is set to .022" cold on both.

Yes alloy heads & alloy block you subtract approx. .012" (depending upon the actual physical size of the engine) from the Hot lash spec, the alloy parts grow more than the hard steel parts

http://www.crankshaftcoalition...usting_solid_lifters

at .022" Cold you could be near .035" Hot, the studs may be getting pounded loose?

Yes, the clearance set cold should be whatever the cam spec is minus .015" with alloy block and heads.

That's how much the engine grows.

Mine is alloy heads on iron block. Cam spec is .022 clearance hot. Cold is .006 tighter or .016 cold.

I would check with the cam manufacturers tech line to get an exact number and go with that. Don't go with just what I say.

Mine is a CompCams solid lifter. The .006" in my case is Compcams number. That's their recommendation.

quote:

Originally posted by SF:
The heads are equipped with insert threads, helicoil.
I have to go through them all. Maybe I go for shaft mounted rockers and skip the guideplates, one problem less, I hope...

I have Crane roller rockers with Crane studs and guide plates that were installed in 1999. I cleaned the stud holes well and used Loctite as recommended by Crane and they have worked fine.

Mike

You don't really say what came loose- lash or the threads into the head. So, two suggestions: with roller rockers, the polylock nut MUST be tightened against the flat part of the pivot shaft. If you tighten against the rounded surface, the nut will indent the round shaft and will quickly increase lash. I've seen this happen in 50 road miles.
Second- by using a stud girdle on the rocker studs, not only will valve lash stay as-set, but the stud will be physically restrained. I've seen cracked rocker studs in a running engine and the driver didn't know it until the engine was torn down for some other reason. Jo-Mar makes a nice girdle assembly which fits the 351-C and also fits inside inside the usual aluminum rocker covers. They work with both hydraulic and solid lifters.

It's the rocker stud that unsrewed itself.

I will check the lash and inform you later on
Thank's so far!
Anders

Here's a pic of my Jo-Mar Stud Girdle mentioned by Bosswrench. I've never had a stud loosen up.

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