Broken Cylinder Stud

jbaeng · 08-20-2005, 09:53 AM

OK,

I was putting the valve covers back on after adjusting the valves yesterday, and out of the blue comes a broken stud with a nut that had a hex drive within it. I had no clue what it was or where it came from (but near the exhaust side of #3 cylinder). After a few minutes it dawned on me it must have been the dreaded broken cylinder stud!

My car has 178,000 miles (an '81 SC) and has been running pretty good. I put a post last week about a very loose distributor and just picked up a used one (thanks Partsheaven) and put it in. It certainly got rid of the hesitation I've been noticing lately when I drove it before I did the valves.

Now the stud issue. My questions are what to expect. I understand the end result will be an engine drop and rebuild, but should I still drive it until more brake? This is very bad timing since I was planning to take it up to Portland next week to start a new job. Also, does anyone know the time it will take for more to break? (I can imagine that after one breaks, others will folow soon since their stress goes up) The last time the valve covers were off was at 160,000 miles when I bought the car and not studs fell out at that time so I assume the broken stud happened some time since then.

tsuter · 08-20-2005, 10:03 AM

Only one broken??? No big deal. Good for 30K more miles of daily driver...but maybe you keep it off the track.

jbaeng · 08-20-2005, 10:41 AM

hmmmmmmmmmmm,

awesome, keep the advice coming!

sammyg2 · 08-20-2005, 11:07 AM

If the broken stud was in the middle of the cylinder bank I would tend to agree, but it it is on one of the cylinders on the end, you will probably do damage by continuing to drive it. the reason is that the cam tower tends to add support to the heads in the middle but not as much as on the ends.
Buy Wayne's book and read it, then you will have a better idea of what you are in for but keep in mind it presents a perspective that leans towards worst case scenario.

On my 1980 engine I had one broken head stud on #4 when I bought it (I knew about it and got a much better deal because of it).
I drove it for a year and a half before taking the engine apart, no damage whatsoever. None. that was with just over 100,000 miles on it.
I was fortunate to have nikasil cylinders which also showed no measurable wear. I replaced the lower studs with 993 steel studs, replaced the rings, replaced all the gaskets, and went thrrough the heads a little. They also were in suprizingly good shape. I also did a few "while I'm in there" things.

All back togehter, it runs great with no leaks or problems. My total cost was around $1000 and alot of that was custom tools and engine stand, which i sold to recoup some of my costs. Of course i did everything myself so no labor costs, except a couple cases of beer

I got off easy and cheap, others have not been so lucky.

Eagledriver · 08-20-2005, 07:26 PM

I'd drive it for awhile. It will nag at you until you get it fixed so you probably won't drive it that way for more than 6 months to a year. You won't be doing any damage as long as there is no gasses leaking from the junction of the cylinder and head. Look at the bottom of the engine and look for oil leaking and soot between the cylinder and head. Until you see evidence of a leak you won't be damaging anything. Once you see evidence of a leak you will slowly erode the metal at the junction. If you erode enough you'll ruin the cylinder or head or both.

-Andy

jtratza · 08-20-2005, 07:42 PM

Just had mine rebuilt after driving about 30k miles with a broken head stud. Stud was on the inside unlike yours though. No damage to cylinders or piston. Only signs of wear were the bottom end bearings but that was not related to the head stud. Glad I finally fixed it though. Now its back to the track without the nagging feeling that something is going to go pop.

Jeff Alton · 08-20-2005, 07:47 PM

I just rebuilt a 3.0 for a customer who put LESS than 2000 miles on his motor with a broken stud. Had to take 12 thou off the heads just to clean up the mating surface. Odds are you will be okay, but be aware you do risk doing more damage....

Jeff

ChrisBennet · ChrisBennet's Garage

Great info Jeff.
-Chris

jbaeng · 08-21-2005, 03:41 PM

Thanks all for the great feedback!!

I was going to take the P car up to Portland with me, but I think I'll let it sit for a bit and bring it up there once everything is moved up there in a few months.

One more question though...

After getting everything all back together, it started right up and runs with no hesitation (unlike prior to the distributor replacement), but when I took it out for a quick drive, it is very down on power. I checked the plug wire on the thought (hope) one was not seated on a plug but to no avail, they were good. I'm confident (but not 100% certain) the valves are adjusted properly, so I'm looking for advice on what else to check. I took off do do the valves, the standard hoses and junk (AC Compressor) to access everything, so I'm not sure what could have beed disturbed. Everyone, put on your thinking caps. One thing I did notice was a mystery wire I found unconnected. I traced it and checked the wiring diagrams but could not identify what they go to. I took some pictures and here it is:

The wires are brown and what I make out as dark white, and the connectors are very small, like they go on small male connector pins. Where should these wire connect to????

I traced the white wire back to behind the relay-fuse area on the left side of the engine compartment to a plug/connector and here is a picture to show it and help identify where the wires above connect to:

I hope this gives everyone the info they need to help me figure this out... Good luck!!

jbaeng · 08-21-2005, 03:43 PM

jbaeng · 08-21-2005, 03:44 PM

wires above and connector traced to below

Jeff Alton · 08-21-2005, 04:13 PM

The two in the first pic look like they might go to the sensor that is on the front of the chain box cover, hard to tell from here though.

Jeff

MotoSook · 08-21-2005, 07:46 PM

Jeff may be right, and it is hard tot ell in that first picture. They may also be the heater blower feed, or they may be the thermo (vacuum) switch feed. Are those connected? Eliminate the possibilities.

jbaeng · 08-22-2005, 01:02 PM

I can't find enything missing connectors. All the ones I remember disconecting to pull the engine appear to be the wider spade type pins and these connectors seam to accept a very narrow or a round pin connector. Does anyone know what sensor/component would have these types of plugs?

Jeff Alton · 08-22-2005, 01:12 PM

Are they two different sizes?

Jeff

sammyg2 · 08-22-2005, 01:57 PM

On my car that connector goes to the heater blower/fan. Doesn't have anything to do with how the car runs.
Does the engine idle as smooth as before? If not you prolly have an ignition or fuel mixture problem. Check for vacuum leaks, then check again

If it does idle just as well as before, you prolly have a timing problem. Did you double-check the timing with a timing light? Do the advance plates in the dizzy move freely?

I assume you don't have any noise from the valves. The only other thing I an think of that would cause it to be down on power after the work you deid would be if the valves were waaaay out of adjustment.
If they were waaay too lose you would hear it, if they were too tight you would prolly have some popping out the intake/exhaust.