How many broken studs are acceptable?

andster · 09-09-2008, 06:08 AM

This weekend I finally found time to adjust my valves. I took off the lower left valve cover and to my surprise found two broken head studs (cylinders 1 and 2). I realize this isn't good and my next thought was is a rebuild warranted immediately? I also wondered how long these have been rolling around in there and thought about putting it back together so that I can drive for a while longer until I can find time to take on the task of a rebuild. Thats the big question; if Im easy on it will the engine be ok to drive for a while or is it a matter of time until the head comes off and my real problems have just begun??

Any advice is appreciated. One other factor is with 4 kids my time in the garage is limited for a few years.

cgarr · cgarr's Garage

I would not run with any broken once I found them, it does not help the sealing surfaces on the heads to run this way, but there are a lot out there running this way. I guess while your driving it now start putting together a plan for repairs.

andster · 09-10-2008, 10:09 AM

Thanks Craig. Im wondering what could go wrong with running it like this.....

Andy

timc · 04:43 PM

Quote:

Originally Posted by andster

Thanks Craig. Im wondering what could go wrong with running it like this.....

Andy

For a while, nothing. (But then who know how long it's been like that, so you could already be past that time.)Then you'll start getting compression leaking, then it will eventually burn/melt the area where it is leaking ruining the Cyl and or Head. How long can you run like this? I don't think anyone can say. If you really wanted to push it, you could drive it until you started hearing the leak, then quit driving it. But you may not hear it in time to save the Cyl/Head. It's a big gamble on your part.

andster · 09-11-2008, 06:33 AM

Thanks Tim. After hearing from a couple of you guys I have resigned myself to a rebuild. I was hoping to get the car on the road after about 8 months out of service. However its best to do it now before it costs me dearly and strands me somewhere.

Andy

timc · 09-11-2008, 07:08 AM

Quote:

Originally Posted by andster

Thanks Tim. After hearing from a couple of you guys I have resigned myself to a rebuild. I was hoping to get the car on the road after about 8 months out of service. However its best to do it now before it costs me dearly and strands me somewhere.

Andy

Well that problem won't strand you, but it can darn well cost you if you let it go!!!!

Brad Beck · 09-24-2008, 11:11 AM

This is NOT an endorsement to continue driving with broken studs but…to ease your mind a little; I’ll shear this story with you.

I recently purchased an 84 with 195K miles showing that was not running, only paid 5k and the car is very straight so I thought what the heck. Found a bad crank positioning sensor, replaced and car ran ok not great but ok, so I decided to drive it for a couple weeks to see what it felt like. When I pulled the engine down I found every cylinder had one stud broken and two cylinders’ had two broken. I think it’s a good bet some had been broken for a good amount of time, and again it ran reasonably well. Five of the heads showed no damage and the one that had damage was still able to be machined.

Again…not an endorsement to drive but…I find it incredible, an engine with no head gaskets could survive running in that condition and have minable damage.

Good luck with your rebuild!

Brad

andster · 09-25-2008, 07:19 AM

Interesting story Brad, and Im hearing more of them. Im sure there are quite a few engines out there running like this and we drive them unaware of the issue. I had a friend suggest a top end rebuild and Im looking into this. A lot will depend on what I find as I get into it more.

Alan L · Alan L's Garage

Generally these seem to get found during PPI. As others have posted, they often run like this undetected for some time.
My SC finally broke two some years ago, so I figured that was enough reason to overhaul the high mileage engine. But one on each cylinder is not fatal. If the engine is still clean around the heads, you probably still have some time/mileage on your side - knowing the clock is ticking.
If it looks grungy and is leaking badly - sooner rather than later would be good.
My 2 c worth.
Alan

Henry Schmidt · Henry Schmidt's Garage

I would suggest that the number is not as important as the location. Two on the same cylinder and you're done. If the outer studs on either end are broken, I would suggest a limited amount of driving with a very soft pedal. If you have one on an interior stud you might be able to drive it for several thousands of miles. How hard you push on the loud pedal is the determining factor. Don't lug it and don't beat on it and who knows?
good luck.

andster · 09-26-2008, 05:51 AM

Thanks for the input guys. I figure with a high mileage engine it will be worth while rebuilding and replacing hoses, fixing leaks, installing the Carrera tensioners, clutch, etc. However, I am considering rebuilding just the top end. Are there typically many more miles to be had out of the case, or is it unwise to perform a complete overhaul at this point? If you have recommendations I am interested.

Alan L · Alan L's Garage

I was faced with a similar situation. My car had about 150,000 miles on it - when I finally had two broken studs. I was waiting for a better reason than just the mileage to pull the engine.
Once out I pulled the top end off to fix the studs. I decided to do whatever was required at that point. The cylinders had no wear - deglaze. The piston ring lands still measured up OK. New rings. The valves had about a 4 thou taper - but the faces were still perfect. Replaced guides and valves. One valve stem was cracked and waiting to fall into the engine.
I then decided to do the bearings - so split the case. The crank really was in good nick. I just replaced all the bearings. Splitting the case doubled the work. You can measure the big end journals with just the top end off - you can pull the rods without splitting the case. I have just (y/day) put the engine back in having done that. The one job I did not do 3 years ago was re bush the wrist pin end of the rods. They were 'OK'. Mistake. Just finished installing after stripping down to rods again.
While case was split also put new chains in - silly not to. Also Carerra tensioners.
The engine feels much better since I did the job. All up, cost me about $US4000 - incl the outwork on the heads - fitting new guides/facing heads. I pulled the old ones, but had the new ones fitted by a shop.
Alan

Alan L · Alan L's Garage

Sorry - one valve guide was cracked - not stem.
Alan

andster · 09-29-2008, 06:47 AM

It sounds like taking the case apart was more work than expected. I just checked out Waynes book on rebuilding the engine and he recommends taking the casing apart when you are at that point (80% there...). My car has had a few surprises so I plan on taking it all apart at this point.

Andy