Need info/advice re pulled rocker stud and probably stuck valves

[CCCC]

1968 with very fresh 327 - but sat quite a bit with only occasional start/warm ups and no road travel due to extended illness. Recently started up fine to load onto trailer for transport - a day later coming off the trailer I noticed miss due to valve issue. Could hear "clacking" - pulled the cover - intake and exhaust on single cylinder not moving because rocker arm studs pulled from head. Now - getting ready to repair.

1. Am I correct to think that the valves stuck and led to the stud pull-out - or??

2. If not stuck valves, what causes the stud issue?

3. My homegrown plan is to run Kroil down all valve guides (to head off sticking elsewhere) and let soak, remove the 2 offending studs and try using a dead blow hammer to see if those two valves will go down easily after the Kroil soak. Is this wise?

4. Want to replace those 2 studs with screw-in type - found the tools/studs online. Have you done this with head still on the block? Probably can trap shavings while tapping, but what are chances of shavings going through the tapped hole (is it open on bottom on original SB 327?)?

5. Is a valve seize event like this an indicator that some others are likely to follow - although I intend to try a run of top end lube after this fix.

5. Hate to do it on such a fresh rebuild, but is it best to take the head - or both heads - off and go though all of them - maybe put screw-in studs throughout? Is such an event anywhere near usual for an older SB design with pressed-in studs.

Thanks for wading through my questions. I need to do this right, but don't want to go into stuff not needed. All info/advice will be much appreciated. I need to get going on this one.

[AussieinNC]

1. Am I correct to think that the valves stuck and led to the stud pull-out - or??

Need more info on spring pressures and cam lift...stuck valves can cause a stud to pull out...but more likely valve to piston impact....or really heavy springs installed.

2. If not stuck valves, what causes the stud issue?

Studs pull out for many reasons...they were probably half out when assembled and missed by builder...

3. My homegrown plan is to run Kroil down all valve guides (to head off sticking elsewhere) and let soak, remove the 2 offending studs and try using a dead blow hammer to see if those two valves will go down easily after the Kroil soak. Is this wise?
Pull the head is the only correct way to fix this issue...and if one head is doing this the other may be close to doing the same...the top of the stud boss needs to be machined flat as a base for the stud to secure against.

4. Want to replace those 2 studs with screw-in type - found the tools/studs online. Have you done this with head still on the block? Probably can trap shavings while tapping, but what are chances of shavings going through the tapped hole (is it open on bottom on original SB 327?)?
Replace all studs when heads are off the engine...check pushrods for straightness....

5. Is a valve seize event like this an indicator that some others are likely to follow - although I intend to try a run of top end lube after this fix.
More an indicator the guide to stem clearance was too tight...top end lube may or may not help...

5. Hate to do it on such a fresh rebuild, but is it best to take the head - or both heads - off and go though all of them - maybe put screw-in studs throughout? Is such an event anywhere near usual for an older SB design with pressed-in studs.

Repair both heads ....replace all studs with screw ins...

[mattfranklin]

x2 on make sure the heads are right.

If you're not super familiar with disassembling the heads, have a good shop do it.

Depending on how much of it you want to do yourself, work that out with the shop.
The last set I had done was done by a really meticulous old-school shop (sadly, the guy retired and sold out the shop during the pandemic). I said I wanted them to do the machine work and I would assemble them. He didn't trust me to get the stem seals in right, so he got those in and inserted the valves and left the springs, retainers, and keepers to me. ;-)

[Thealien]

I agree with fixing it right. With that being said I used to have an old Mustang and the rocker arm studs would occasionally pull out. I had the old T handle valve cover bolts and I got pretty good at taking the cover off tapping the hole and installing a screw in stud and getting it running on the side of the road. Not the correct way to do it but just letting you know it can be done. I was a young dumb 17 year old kid at the time.

[57taskforce]

I’m not sure where Casi Cielo is but I’ve got a good machinist friend here in Farmington. I could probably set you up with a great deal to get those heads fixed. He does all the machine work on my personal builds and the industrial stuff I build at work.

[Bigdav160]

The easiest fix would be to drive the stud back down and pin it.

Trying to convert to screw in studs without real machine tooling usually ends up with studs that are slightly misaligned.

If the cam is big and the rockers bind that can pull the studs (damhik)

[CCCC]

Originally Posted by Bigdav160

The easiest fix would be to drive the stud back down and pin it. - - - -

Because this rebuild has no more than 200 miles on it and the problem happened only on one cyl, I am tempted to think that maybe the rebuilder didn't get those studs correct. Consequently, I could try your "easiest" fix, and always can go deeper - the whole head route - if the problem persists.

Can you give/send me a description - or cite a video/article/etc. - that shows how to pin a stud in that manner.? Thanks a bunch for ny info.

I have been driving and fixing my own stuff since 1954 - including a number of Chev/GM engine rebuilds - and, believe it or not, this is the FIRST time I have encountered a popped stud. I was happy to get this truck because the engine had been re-done by a reputable guy.

57taskforce - I may reach out to you on that guy in Farmington.

[LockDoc]

-
I have pinned studs before with good success. I just drove the stud back in, drilled a hole through the boss (I think I did 1/8") and into the stud and drove an 1/8" pin in it. I used music wire for the pin. May not be the correct way to do it but it works if you need to get a vehicle running on a weekend.

LockDoc

[Myself]

Are the pushrods still moving? I'm worried about your camshaft lobes if it's flat tappet.

[CCCC]

Originally Posted by LockDoc

-
I have pinned studs before with good success. I just drove the stud back in, drilled a hole through the boss (I think I did 1/8") and into the stud and drove an 1/8" pin in it. I used music wire for the pin. May not be the correct way to do it but it works if you need to get a vehicle running on a weekend.
LockDoc

Thanks LockDoc. I had gone out and looked at the situation before seeing your post and had figured that would be the way to do a pin - was thinking about how to get the correct angle setup.

To answer earlier inquiries - valves, springs, cam and other components are stock spec. Yes, push rods are operating, rockers look good, etc. - just two adjacent studs up enough to defeat valve action.

Really sharp looking, clean old Sub in excellent shape, very solid mechanically, unexpected and previously unexperienced problem, and an old shade tree guy just wanting to jump in and fix it himself as always.

Need to move on this and simply abhor the thought of dismantling the top side of such a fresh mill. The folks that sell these kits say they work well, but am hearing solid advice here that the intended method (hand-threading for new studs while leaning over the engine) is probably not the best way.

Maybe I will just try the less invasive pin method and see if that holds. Thanks very much for all replies and advice.

[mattfranklin]

There are also tools like this to help you get the tap straight if you decide to go that route:
https://www.summitracing.com/parts/sum-900136

[RustyBucket]

Have you determined if the valves are free in the guides? If the valves are closed and sealing You can air pressure the cylinder off of your compressor to hold them closed. Then disassemble the keepers, retainers and valve springs, just make sure the piston is far enough up the bore so the valves don't fall into the cylinder when you release the air pressure. You'd be able to determine if the valves are bent or stuck in the guides. Were the valve springs replaced during the rebuild? Many years ago I put some stronger springs on a '64 GTO & pushed rocker arm studs out. Carefully re-seated them... with a hammer... drilled holes off center just catching the stud slightly. I drove small roll pins into the holes. I had a fitting that screwed into the plug hole connected to my compressor. Did all 16 rocker studs. Worked good, wish I had the GTO back.
re-reading some of this thread, as I recall I drilled smaller holes than LockDoc.

[CCCC]

Thanks RustyBucket - very helpful thoughts and info. The valve springs were new on rebuild and are supposed to be stock item - not the heavier tension type you used on your GTO. I may be able to verify that when I get those out.

I have the fitting for the spark plug opening - have spun the crank and the piston is about 3/4 up, and soon will pressurize the chamber (I think the valves are seated OK) so I can remove hardware and check valve freedom.

LockDoc's post inspired me to try the stud pinning fix and, in my mind, I think I can envision the way you pinned yours. I need to search around a bit to see what I can find for a proper dia./length roll pin. 1/8 looks a bit big to me, but what do I know?

If any of you know of pics or a video on pinning studs, I would love to see some. A very knowledgeable and capable son in law will be visiting me later this week and maybe we can get this done - at least part-way.

And, thanks mattfranklin - the tool you cite is with one of the kits I referred to earlier. I may wind up threading - we shall see.

Thanks to all.

[mattfranklin]

The one thing about pinning the studs is that once you go that route, that is a weak spot. If you ever want to upgrade those heads with stiffer springs, screw in studs, guide plates and all that, then that's something to think about. But if these heads will never be taken beyond stock, then all is good. Just want to make sure you have all of the information before you make your decisions.

[CCCC]

Thanks mattfranklin - I did realize that and appreciate your note. The 327 in this Sub is not going to be further modified in any way for as long as I and our kids have it - which will likely be a very long time. In general and for normal purposes, I think the 4bbl 327 is the best of the SB Chevs and I just want this one correct and running great.

Those who have contributed to this thread have been very good - quite helpful to a guy that just tripped over a first-time problem.

Thanks.

[CCCC]

Ok - looked closely at the whole thing and felt that I cannot very easily drill/pin the studs to the head without removing the head. Maybe someone more adept and expert than me could do that.

I knocked the risen studs to bottom and was able to turn the nuts off and remove the rockers. Looked at all studs and some seem like they may not be down completely. Looks like a poor job on those by the re-builder.

So, the heads would need to come off anyway, even if I wanted to pin them. I don't. Will find a good head work machine shop and have screw-in studs installed. A shame - barely driven 327.

Thanks for all the suggestions.

By the way - I removed the two push rods along with those rockers because I need to run the truck long enough to move it to another stall. But, now, it will not run at idle speed - dies below about 1k rpm. So, question: Will a dead intake and exhaust on one cylinder reduce vacuum - or do something else - to the degree that this SB will not idle? If that's not the problem, something in the idle aspect of the Holley suddenly has gone kaput.

[1968k20]

I worked many years in the machine shop trade. If the heads were “baked” in an oven, this can cause the studs to pull out. I would start over with different heads if it were me.

[mattfranklin]

I had a similar idling issue when I forgot to connect a vacuum line. It was a large one for the PCV hiding under one of the bowls (rear) of my Holley 4bbl.

Originally Posted by CCCC

By the way - I removed the two push rods along with those rockers because I need to run the truck long enough to move it to another stall. But, now, it will not run at idle speed - dies below about 1k rpm. So, question: Will a dead intake and exhaust on one cylinder reduce vacuum - or do something else - to the degree that this SB will not idle? If that's not the problem, something in the idle aspect of the Holley suddenly has gone kaput.

[RustyBucket]

[QUOTE=CCCC;8876235

By the way - I removed the two push rods along with those rockers because I need to run the truck long enough to move it to another stall. But, now, it will not run at idle speed - dies below about 1k rpm. So, question: Will a dead intake and exhaust on one cylinder reduce vacuum - or do something else - to the degree that this SB will not idle? If that's not the problem, something in the idle aspect of the Holley suddenly has gone kaput.[/QUOTE]

I wonder if it'd run/idle smoother if you took the spark plug out of the dead cylinder. Might sound awful but maybe run better to move the truck. Don't see what it would hurt to try.

[AussieinNC]

I dont want to be the bringer of bad news, but I feel its a really dangerous process to remove pushrods and rockers and then start an engine....

The cam followers rely on some valve spring pressure to maintain contact with the cam lobes....without the spring pressure there is a good chance the lifters are floating up and down and being beaten up by the cam lobes....

Worst case scenario would be if a lifter came fully out of its bore, this would open up the lube circuits to a massive internal oil leak....

With the studs pulled up, there is most likely bad wear on the corresponding cam lobes....suspect made much worse now by letting the lifters float free....

[CCCC]

Originally Posted by AussieinNC

I dont want to be the bringer of bad news, but I feel its a really dangerous process to remove pushrods and rockers and then start an engine....

The cam followers rely on some valve spring pressure to maintain contact with the cam lobes....without the spring pressure there is a good chance the lifters are floating up and down and being beaten up by the cam lobes....

Worst case scenario would be if a lifter came fully out of its bore, this would open up the lube circuits to a massive internal oil leak....

With the studs pulled up, there is most likely bad wear on the corresponding cam lobes....suspect made much worse now by letting the lifters float free....

I appreciate this post - don't know the possible outcome because I never have run an OHV engine with any push rods removed. Even though the run would only be about a minute or so, I need to look into this thought.

All told, the engine has only run for three minutes or less once the studs popped up - was removing it from a trailer and simply ran it into the garage and shut it down once I felt the miss and heard the rattling rockers. I can reinstall the push rods and rockers to run it into another stall - not much to do there - but this non-idle has kicked me in the can in the midst of the valve stud issue.

Thanks mattfrankliin - I have checked every vac leak possibility - and will do so again, PCV line was installed/tight - vac to PB booster is from manifold and it is secure.

Thanks 1968K20 - never have had heads "baked" and do not know if these were - why is that done and what is the effect? Even so, would you not go to threaded studs with these heads? I'm old - but a learner.

[Myself]

Now it won't idle?.....I swear I've been down this road. Please pull your oil filter and cut it open. Look for metal in the paper pleats. Report back.

[CCCC]

Originally Posted by Myself

Now it won't idle?.....I swear I've been down this road. Please pull your oil filter and cut it open. Look for metal in the paper pleats. Report back.

This sounds ominous - and certainly will check for loose pieces if the idle problem can't be solved with carb work and zero vacuum leaks. What is the potential problem you are addressing - or, what happened in your case?

No one has spoken to the possible effect upon normal idle in the case of two non-working valves (one can dead). Any experience there?

[Myself]

I had a pretty fresh 355 sbc. Started with a popping/misfire. Led me to find pulled rocker stud......then 2 loose studs maybe 50 miles later.....then trying to troubleshoot noticed it didn't want to idle and when I shut it off I noticed the fan would stop IMMEDIATELY, like it had brakes!! Found metal in the oil filter and pulled it for teardown.....wiped out 8 cam lobes....ruined all the cam, main, and rod bearings. Rebuilt it all over again.

Inexpensive and relatively quick to cut open the oil filter. Rule it out for piece of mind.

[mattfranklin]

The dead cylinder would make the engine less able to try to spin against the friction. Friction of all 8 cylinders would be similar, but you have only 7 firing to overcome it. Analogous to how it would idle more poorly if you had just pulled a plug wire. (If you want to dig more into the theory you could look up terms like PV diagram, imep, bmep, fmep, thermal efficiency, and mechanical efficiency. I thought it was pretty cool stuff, but it's not everyone's cup of tea.)


The issue that "Myself" (it feels funny to say that word without actually referring to myself) was talking about is a huge increase in friction caused by component failures and metal wear particles getting into everything as well as a power decrease from those failures. My guess is that you don't have that issue, but as a quicker check, take a look at the oil and look for sparkly things. It's never a bad idea to check the filter, but I don't think I've ever cut one apart. I had an engine fail once, but I didn't need to look inside the filter -- all the burned bearing pieces and broken rods sitting in the oil pan told me that. ;-)

Originally Posted by CCCC

This sounds ominous - and certainly will check for loose pieces if the idle problem can't be solved with carb work and zero vacuum leaks. What is the potential problem you are addressing - or, what happened in your case?

No one has spoken to the possible effect upon normal idle in the case of two non-working valves (one can dead). Any experience there?