Assumed Broken Head Stud

TCGGrafix · 12-18-2001, 08:12 AM

I started to notice a strange metallic rattle when I drove over bumps. It sounds like I had a large bolt in an empty coffee can. I looked around but couldn't find anything loose. Last weekend my wife and I took the Pcar for a weekend trip from Chicago to Indy and while turning onto an onramp and giving it some, I hear the dreaded clap like sound. It matched the exhaust sound. It would appear right around 3000 RPM under load but didn't seem to do it in 4th or 5th gear. Never the less I strongly suspect the notorious broken head stud(s) I am going to take off the exhaust valve covers and check for any loose studs in the next few days. I don't have a garage at my house to work in so I am going to have to send it in to a wrench. My question is does anyone recommend a good shop in the west suburbs of Chicago (Naperville area)? And what should I expect to pay for replacing all the studs? Car runs great otherwise with very little oil consumption and no leaks. Thanks for your advice!

osidak · 12-18-2001, 08:17 AM

I paid $2,600 to replace the 12 exhaust studs and have the heads fly cut.

I am in NC and the car was a 78 911sc

osidak

rstoll · 12-18-2001, 08:45 AM

Might try a bottle of techron and some premium fuel first.

TCGGrafix · 12-18-2001, 10:24 AM

Thanks for the replies. I allways use 93 octane in the car. I have heard of people using the Techron additive. Is it supposed to break up carbon deposits? Could it be possible that carbon deposits could be causing the noise/problem? Thanks agian for your help.

emcon5 · emcon5's Garage

Before you assume the worst, go bang on your cataleytic converter a few times with the engine off. It could be the core of the cat is coming apart.

I had a truck that had a similar noise, and the cat was the source.

If it is a broken stud, there are a few people on this board who are still running fine with 1 broken head stud.

Tom

Don Wohlfarth · 12-18-2001, 12:05 PM

Around 3K was the rpm I heard the same sound. Found 3 broken studs. Sounds something similar to a loud muffler. This is on a 82SC with 115K on the clock.
When it starts getting louder it's the head bouncing off the cyclinders.
If it's the studs you've got a couple choices, replace only the broken ones (bad choice #1), replace only the exhaust studs (uh, maybe), replace them all.
I used Raceware and replaced them all. Used this as an excuse to rebuild the motor so I can't give you a price.

5axis · 12-18-2001, 12:15 PM

Check out Kautz in Geneva 630- 232-8241, or for something a bit racy try Midwest eurosport in Bensenville 630-595-5577.

rstoll · 12-18-2001, 12:41 PM

The techron will break up the carbon deposits that may be causing detonation. Worked for me in my 83. Catalytic suggestion is good too.

CamB · CamB's Garage

I have a pretty bad leak between heat exchanger and muffler which causes the same sound - worth checking that too (in your case it will be heat exchangers to cat or cat to muffler).

Cam

Superman · 12-18-2001, 02:09 PM

These people are telling you to thoroughly check everything out before you go assuming a head stud problem and tearing amotor apart. I agree.

The metallic rattle could be a failing chain tensioner. They say this sounds like a chain being dragged across a metal garbage can. but usually it is present at idle. I think it's more likely that the guts of the CAT have come loose.

I think the dreaded clap may be a different noise and possibly a different source. So, you may be looking for two problems. Look look look, before you decide to rebuild your engine. FWIW, I have been knowingly driving on a broken head stud since last spring.

beepbeep · 12-18-2001, 07:10 PM

First of all....please understand the difference between "head stud" and "exhaust stud".

"head stud" bolts head to the case...if one breaks you can hear exhaust gases escaping. Mucho $...but not so serious as it sounds.

"exhaust stud" is 8mm stud used to bolt heat-exchanger flanges to the head. They brake all the time. When they do, you'll hear gases escaping trough gasket. Nothing serious...just have them pull down heat-exchangers, extract/drill the stud and helicoil/timecert stud holes.

If you are a real buff, pull out all studs, timecert all holes and put in new studs with new gaskets. Works great for me...

In your case , It's probably exhaust studs....

How to check? Raise the car and strat the engine. U half meter of rubber hose with one end in your ear and move other one around until you find leak-source.

Cheers!

RoninLB · 12-18-2001, 07:38 PM

I'm w/ Superman completly on this one...for bs -- my broken head stud was good for 20,000 with no popping/leak before rebuild.

TCGGrafix · 12-19-2001, 10:42 AM

This board is great with great people to match. Thanks for all of the suggestions! I will tinker around with the car in the next day or two. If I do discover any broken head stud(s) I have conflicting opinions regarding if any damage could be done to the heads or cylinders. I have heard it is fine to drive if only for short distances, drive it lightly, ok to drive it if it only has one broken stud per cylinder, ect. (Hope not to start another debate.) Even if I drive it and do damage can I damage it beyond repair? (Re-machining the heads and cylinders surface) Anyway, I still think I would want to repair it as I too have Obsessive Compulsive Porscheitis (OCP). I would think the performance would be affected and that would be difficult to know and live with. Still looking for anyone else that can give me an idea what replacing all the studs in the Chicago area would cost. (Also, if anyone could provide the cost for a total rebuild in the area that would be helpful as well.) I know I appear to be lazy by not calling around to get my own estimates, but I have called 3 different places. So far none of them have returned my calls or called back with an estimate as promised. This is not encouraging!

If anyone is interested in doing a tandem rebuild, in the Chicago area, courtesy of their garage, I will supply the manuals and all beer required to see us through completion

Thanks Again!

Superman · 12-19-2001, 12:07 PM

Someone take this guy up on his tandem rebuild idea, if he still feels like he needs a rebuild. Wayne feels that one broken head stud is not a big problem. I am anxious to fix mine, but have driven on it for many months now (I can't resist driving this car!). John Walker will probably be able to tell you of many, many instances where broken head stud problems have damaged engine parts.

It's cheaper to rebuild a motor of the parts are not damaged, but yes, parts can be repaired or used replacement parts can be found. There isn't anything on these cars that can't be repaired.

ovilla · 12-20-2001, 12:08 AM

Call Motorwerks in Barrignton, IL. It's a huge multi-fancy dealership that sells P-cars, BMW's, Benz's, and even Rolls Royce's. Anyway, had all of the exhaust studs on one side of a 914 replaced after one had broken off. Paid a little over $300 for that work. The mechanic that works on all 914's and olders 911's is a guy named Gene. This guy is really careful and pays attention to detail and you can even call him to ask questions.

TCGGrafix · 12-20-2001, 05:59 PM

Thanks for all the great replies guys! I got my answer today. Here is a link to my new post showing the gore. http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=54859 Well. I guess what I had suspected was correct. I never would have thought anything of it if I didn't have access this great BB with very helpful people and information. Thanks again!