While I'm in there advice needed

Bullet Bob · 09-07-2007, 11:05 PM

I purchased this car a year ago and other than minor maintenance it has ran fine.

I recently pulled my engine and tranny to replace the clutch because the rubber center gave way ('88 Carrera, 190k miles) and I figured I would pull the heads to fix a small oil leak between head 2 and the cam housing. Once I got everything apart I noticed that one of the head studs (cyl 6) was broken. Everything appears to be fine but I am not sure how to proceed or how far I should go with this.

Would it be unwise to just replace the one broken stud, or should I do all of them? I believe they are stock but I could be wrong. Also, this case doesn't have any timecerts etc... Does it need them? I would really prefer not to go there just yet.

Since I have the heads off should I go ahead and tear them down, inspect, and rebuild them as necessary? This car didn't have much of the service history documentation to go with it but it was well taken care of from what I could tell. I'm sure the top end has been done but I don't know when.

I have bought a lot of parts (headers, exhaust, etc...) already and rebuilding the top end would get expensive. It is a lot of work to get things apart to this level though so I am tempted. What is the bare minimum I should consider doing? Any thoughts would be appreciated.

Thanks,
Bob

HarryD · 09-07-2007, 11:57 PM

Hi Bob,

You already have it apart and you will need to repalce the broken stud. In my mind, it would be prudent to replace the others (I am not sure but you may need to do only the exhaust side studs - do a search) as well since you already are in there. I would also send the heads to a machine shop to get them inspected/renewed as needed as I would suspect your valve guides are worn.

You have an aluminum case and you "should" not have the issues that us guys with magnesium cases have with the studs pulling and damaging the threads. If the threads are ok, I would not think you need timecerts.

Some of our more expert rebuilders can most likely give you more definitive answers.

JoeyD911 · JoeyD911's Garage

Do you plan on keeping the car for another 190K? A broken #6 head stud has me considering a total rebuild at only 60K! The labor charges or time you'll spend yourself isn't all that much more if you're already down to pulling the juggs and studs from what I can tell. Hope it all works out ok for you.

efhughes3 · efhughes3's Garage

There is no way you can take a 190K engine apart for studs and not rebuild.
You, at absolutely bare minimum, will need to do the top end. But, to not open the case to inspect, refurb and replace bearings, rod bolts, etc is not a wise decision...

hcoles · 09-08-2007, 06:22 AM

FWIW - re. heads/etc. find the best possible place to check/redo the heads/rockers/rocker shafts/etc. While you are in there might as well regrind to 964. I would contact camgrinder (John) and get a complete package done. He will reface the rockers for the new cam surface. IMHO this will give you the insurance aginst the two common issues... "valve train noise" and rocker shaft leaks. I replaced the head studs with all steel and got rid of the dilvar. I also put in new valve springs. John and suggest on that. Also IMHO check that valve seats are cut by a Serdi type cutting machine. I think this gives the best results. There are a number of decisions to make but as mentioned above since you are this far, might as well rebuild the motor and then drive happy for the next 150k miles or so.

Bullet Bob · 09-08-2007, 07:05 AM

I would like to keep the car for a while and I would also like to get it driving in the near future. This is my daily driver and I put 20k per year on it. Currently I am driving my POS Dodge truck as a substitute and it is not fun.

What are the typical lead times on having the heads done?

Bullet Bob · 09-08-2007, 07:14 AM

Also, the engine mounted oil cooler is pretty dirty. Can these be sent out to be cleaned or do I just live with the dirt? I am hesitant to just throw it in my parts washer because I fear that the crud and dirt will get trapped inside.

I am having all of the metal powder coated and cleaned etc... I would like this to look good when I am finished.

hcoles · 09-08-2007, 07:40 AM

IMHO - this is sort of the wrong question... regarding times, it all depends. I think John Walkers workshop is in your area, you can get a quote from him. You may read in many places on this site that patience is the key or one key to success... when you ask for lead times at this point, I feel like you are starting on the wrong foot already... It is a trade off, you want it done fast and correct, you pay a professional to do it, you want to DIY and save money (maybe) then the time to completion will likely be different... there is no way to make a magic situation out of this, there are a lot of parts to make decisions on and quite a bit of learning to be done. Of course you have to order parts/buy tools/etc. I think unless you are an experience mechanical/technical type, have patience and will take the time to do all the reading, the risk of a mistake is considerable. Others are free to jump in and tell me I'm all wet... it's just my feeling on the subject.

hcoles · 09-08-2007, 07:44 AM

you can't just throw a hex in a parts cleaner unless it is sealed and you are just cleaning the outside, if you think you can throw it in a parts cleaner and the inside will get cleaned then I think you don't know enough to do this project.... there are so many threads on each question you have.... probably you need to take some time and do reading. The first thing is to buy the Wayne book and read every word a number of times. This is an education start.

JoeyD911 · JoeyD911's Garage

If you are dead set against the rebuild, this is what I would do. Put the clutch in, forget the cyl small leak and head stud. Give it a good cleaning/polishing and just paint the things you're thinking of PCing. The stud may have been broken for the last 20K, whose to say it won't go another 30. You'll be damn near a quarter million miles by then, Go in and do the whole job then or ditch the car. Just my humble opinion.

kepperly · kepperly's Garage

Several things need to be addressed at the point you are at.
cyl., ring and piston wear
intermediate shaft gears and bearings, these seem to wear out before the mains and rods.
cam gears, chains and tensioner, new cam oil lines, CHECK YOUR FUEL LINES
THEY ARE NEXT TO IMPOSSIBLE TO REPLACE ONCE CAR IS BACK TOGETHER. Don't spend the bucks for stock Porsche lines look for articles on making your own.
Again at the point you are at, minimum new guides, seals, valve job. The on engine oil cooler can be cleaned externally with a parts washer and compressed air. Seal the inlets before starting to clean then when done just reinstall with confidence ( you have been keeping your oil clean right) USE
New green o-seals on cooler. On your car its common that only the bottom row of head studs were delvar and the top ones steel. Just replace the bottom ones with the stock steel available from pelican. If you are just going to do the top end DO NOT even crack the rod bolts or you should replace them all. Get the right sealers, fasteners and gaskets and pay attention to the torque values.

Keith Epperly
87 slant nose turbo look carrera cabriolet

Bullet Bob · 09-08-2007, 08:03 AM

I really didn't tear this engine apart to rebuild. It was supposed to be a clutch job. In asking about lead times I am just trying to get a sense of the time costs for planning purposes. If it will be 6 weeks that is too long. I will fix the stud (already removed) put it back together and do a planned rebuild when it is really needed. If it is only a few weeks then maybe I will go ahead with it now.

I have all of the relevant books (Wayne's, Haynes, Bruce Anderson) but they all have their limitations. There isn't any substitute for having done it before. When mentioning that the cooler is dirty it is all external and I realize that it shouldn't be thrown in a parts cleaner. How do most people approach cleaning one of these? It is pretty much for cosmetic purposes and if it is more trouble than it is worth I can live with the dirt.

I have a mechanical background but as you know there are a lot of details... Thanks for the help!

Bob

efhughes3 · efhughes3's Garage

Take your oil cleaner in for cleaning and testing. Maximum $200.

Bobboloo · Bobboloo's Garage

Bare minimum replace all the bottom studs.

What is your oil consumption? This will tell you whether you need to rebuild the heads or not.

kepperly · kepperly's Garage

I believe I am one of the most anal people around when it comes to motors,
but when it comes to an oil cooler on the block of a 911 there is alot of money wasted by cleaning methods. Lets assume like most of us the coolers seals leaked and caused dirt build up and reduced cooling. If your motor did not suffer from a failed part that spread debre though the motor then what purpose is served by having it internally cleaned. The sealing surfaces around the o-rings and the cooling fins and shroud should sufice any external washing. Seal the inlets and outlets and wash in solvent or in your parts tank.
Then blow off excess solvent and wash with hot soapy water to prevent " NEW" dust from adhering to the left over solvent. Use some curil t on the new o-ring and reinstall with lock nut to the exact torque. Saved me $200.00 and anything in the motor gets washed out and into the filter which is change at 500 miles anyway. When you put it back together add GM- EOS !too.

Keith Epperly
87 slant nose turbo look carrera cabriolet

Bullet Bob · 09-08-2007, 08:25 PM

My oil consumption was around 1qt per 3k miles, if that.

Bobboloo · Bobboloo's Garage

That's good.

If I was in your shoes and the oil pressure also looked good I would just replace the studs and put it back together but that's just me. Many others have their opinion and I am by no means an expert but I just feel that fixing the stud is needed to prevent risking damage to the heads and if the vital signs are good otherwise then just button it back up and drive it.

Save a rebuild for when it's necessary or at least for when you want to modify the motor.

Bobboloo · Bobboloo's Garage

That's good.

If I was in your shoes and the oil pressure also looked good I would just replace the studs and put it back together but that's just me. Many others have their opinion and I am by no means an expert but I just feel that fixing the stud is needed to prevent risking damage to the heads and if the vital signs are good otherwise then just button it back up and drive it.

Save a rebuild for when it's necessary or at least for when you want to modify the motor.

HarryD · 09-08-2007, 09:33 PM

Quote:

Originally Posted by Bullet Bob

My oil consumption was around 1qt per 3k miles, if that.

At that low oil consuption, I would think that you do not have worn guides etc. (Your first post did not provide that info.)

I agree with Bobboloo and would limit my scope to replacing the broken stud and if budget permits, replace the other exhaust ones, button it up and press forward.

efhughes3 · efhughes3's Garage

Quote:

Originally Posted by kepperly

The sealing surfaces around the o-rings and the cooling fins and shroud should sufice any external washing. Seal the inlets and outlets and wash in solvent or in your parts tank.

That's what I thought too. But, i wanted to get all of the built up gunk cleaned well out of the cooling fins, so I took it in to an aviation shop. They pressure tested and found a pinhole leak. Guess where much of the crud in the fins was coming from?

How long do people think oil coolers last without some sort of failure? Spend the $200 and do it right. Mine only cost $170. It looks brand new.