geostasis

Hello. I have a 1988 Carrera (@ 95K miles) which has at least one very chattery valve. When it's just starting up cold, it's very pronounced at low idles, and it moderates pretty well when the engine warms up. The car uses oil at around 1 qt/1000 miles, and is on the whole in excellent shape.

I had the car in to the mechanic recently and he let me know that it was getting close to time on getting the top end done, and that I should plan on budgeting $6-$8K for the work from start to finish. Between my surprise (I figured $3500 - $5K), and needing to rush off to an appointment, I didn't have the chance to dive into what made up this figure beyond valve guides and doing the clutch (original g50 clutch, probably well due for work/replacement of components).

I expect to go back to my mechanic and get a detailed list and estimate of what he would plan on doing, but I'd like to first build up a basis of understanding so I can have an intelligent conversation.

Has someone else gone through the top end exercise recently? If so, any gotchas or hard won lessons would be very appreciated. Thanks all in advance!

David911

I had my top end done and it cost around $9K+. It all depends on what you are having done. In addition to the normal stuff, I had ARP rod bolts, EBS valve spring kit, polishing the intakes, and 964 cams. I also had the clutch fork update, and a couple of new oil lines. I considered all of this "while you're in there" type work, and you could adjust your expense to fit your budget.

One thing I was surprised by, and not happy about, was the parts cost was significantly higher than you could get from say, pelican parts. The mechanic had his sources, and was not going to use someone else. I think this is part of the deal if you don't do the work yourself.

Something I was not surprised about, but I did not like, was that the job took about 6 weeks. I had planned for this - I had the work done in the off season, but it was still a long time. If you mechanic is a smaller shop, the job could also be subject to various "emergencies", i.e. other projects, that could extend the time further.

I am very happy with the work done, the car really pulls better than it did before.


David

HarryD

I would have your wrench explain why you need to do a valve job now and what are the consequences of waiting. He should provide you with some test data (compression/leakdown) and visual observations to support the need for the rebuild.

My '73 had badly worn valve guides when I bought it at 108,000 miles. It used 1 qt oil/300 miles. My compression was ok but leakdowns were a bit low. You saw a bit of smoke on startup and copious smoke on decelleration. No smoke on acceleration. He suggested I wait and buy oil.

Due my growing concern of valve failure (I autocross and try to get to redline whenever I can) I finally decided to rebuild at 117,000 miles. Even then, my wrench suggested I could still wait.

I was going to do the rebuild myself as I was unemployed and had lots of time and access to a good place to work. Upon ordering the parts and getting ready to drop the engine, I got a job offer and my rebuild plans were dashed. I discussed my supplying him the parts I had already purchased. He was agreeable but told me that the work would not have a warranty then. I have no quarrel with his position (do you bring eggs to the restaurant for the cook to prepare?) and figured the additional cost of the parts was worth the price of a warranty.

It is a tough call. He gave me a base price and when we were done, we were $1,800 over his $3,500 estimate due to my need to buy 12 valves, replace my clutch (including resurfacing flywheel) and install carrera tensioners. This returned my stock 2.4 L to stock condition. He had my car for about a month.

You may want to get and read Wayne Dempsey's "How to Rebuild Your 911 Engine" book as well since it will help you understand what your wrench is talking about. I found it quite enlightening and I think it helped me ask intelligent questions.

Richard Pankhurst

I am in the process of doing a top end rebuild on my '89. I bent 4 exhaust valves and upset the valve guides on the track. The car was down on power and idled a little rough but otherwise ran fine. We found the problem after a leakdown test (90% leakdown on the offending cylinders) and a compression test (40 PSI loss on the offending cylinders) I would not have removed the heads on my engine if the leakdown & compression test had not been really convincing.

The head work and some other work has taked one month and I expect to get the car back this Saturday. I expect to spend +- $5K for the whole job. I had to replace cams as well due to some unusual wear on 3 lobes on the left cam.

With good oil consumption like yours I would recommend that you first dyno the car, then do a leakdown and compression test. If those tests show no major issues then run the car until it either breaks or those tests show significant deterioration. Remember a decent condition 3.2 engine costs $5 - 7K. The only reason I rebuilt mine is that I am going club racing.

Think carefully before jumping into this one...

Swiss911

I had the top end done on my '87 Carrera last year when oil consumption was reaching 1 liter per 350 miles. The car still ran well but it was obvious the oil control rings were not up to par. I spent about $7,500 to replace valves, guides, springs. I also replaced the cam with a 964 model and installed new European spec nickasil pistons/cylinders with a higher compression (they had 18,000 miles on them and came off of a car that had been crashed -- cost $1,500). So all in, x piston/cylinders my rebuild cost $6,000.

I spend another $2,500 on a new clutch, some exhaust modification, new fuel lines, reprogramming the ECU and a bar that fits between the two shock pillars in the front to add stiffness.

The car runs noticeably better although not sure how much improvement is from which mod. Power band is wider, torque is higher (+20nm), and hp is up to 245 compared to 231 for stock Euro configuration. My mechanic is promoting a mass air flow system and I'll take a look at that later this year.
All in I'm very pleased with the rebuild.

pig4bill

A reminder that geostasis is in the SF bay area. Typical labor rates for BMW, Porsche, etc shops is $100-$125 an hour, with some charging even more. In that light, maybe $6-8k is not so bad.

john walkers workshop

i did a top end on a '89 last week. it took me 3 days. all new valves and guides, rings, rod bearings, and clutch parts. the bill was $5400 incl. tax. don't know why it should cost $8K.

Jim @ EuroWerks

In most owners manuals (porsche ) 1 qt of oil per 1000 mi is considered normal. Did anyone try adjusting the vavles? High oil consumption is 1qt per 500 miles.If you are to this point, when you do the top end go ahead and replace the rings, rod brgs, and case bolt o'rings.When the o'rings are done make sure and do one bolt at a time toquing each before loosening the next.