Rebuilding my '83 3.0
 

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After discovering a broken head stud a couple weeks ago, I spent Thanksgiving doing two things. Roasting a turkey on the Weber, and dropping my engine. Later this week I'm planning to open up the top end and see what I'm facing.

In the meantime, I've been reading up on possibly perfomance upgrades. If anyone wants to chime in on a similar experience with their SC, I'd listen eagerly.

Here's my experience with driving 911's and aircooled's so far (I don't/didn't own any of these cars except the bug and my 911.)

1971 911S. First 911 I ever drove. At first I wasn't so thrilled, maybe because I didn't feel so at ease with the owner of such a valuable car riding along. Drove it a second time a year later (alone!) and it pretty much hooked me on the spot.

1984 low mileage Euro Carrera stock. Couldn't really open her up with the salesman riding shotgun in Atlanta traffic. That drive sort of was a letdown.

1984 low mileage US Carrera, stock. Drove what I think a new car would drive like. So smooth. Great car for touring.

1980 SC Weissach with SSI's, sport muffler, PMO carbs. This was a blast to drive. Great sound, great throttle, great power. A little loud. (Awful interior!)

1970 T Targa, original owner car with 60k miles. This was fun, and if I could afford a longhood, I'd be satisfied with a T if that's what I ended up with.

1979 SC stock. Definitely peppier and lighter feeling, more revvy and responsive than my '83 SC. Perhaps because of the larger ports and maybe just running better?

1969 VW beetle 1776cc with dual Weber 40's, lightened flywheel, 110 cam, A-1 exhaust. This thing pulls like crazy, but is incredibly loud. Too loud! I build this engine from scratch last year with my brother and 12 year old nephew.

Finally, my car. '83SC with 117k on the clock. I've enjoyed putting 7000 miles on her this year. But in retrospect, comparing to the other cars I've driven, I think mine needed a little help. It had okay compression, but three cylinders were leaky at 33% and 13%. Plus, the busted head stud probably didn't help.

So here's what I'm thinking. I want to bias this rebuild towards longevity, reliability, smooth power, a little increase of power without violating the other principles, and without breaking the bank (I know, I know...)

I've read the forum, Anderson's Performance book, Wayne's books, and as much as I can find on the subject. So here's where I'm at, unless I find my P+C's are actually in good shape (I know at least one needs reringing.) These are the performance upgrades, I'm assuming I need a valve job, guides, etc. That's just rebuild stuff, not mods.

- Have my Alusils replated with Nikasil.
- JE CIS pistons to take CR to Euro 9.8:1
- Regrind cam to 964
- Backdated exhaust--SSI's with OEM Dansk 2in 1 out muffler
- Keep the CIS

Here's my goal. A fresh, nearly stock 3.0 with a little more punch, without adding noise. As much as like a sport muffler, I know I will tire of it. I plan to use this car to do some longer road trips, and I don't want any more noise than it makes now. If I want a loud, raspy ride, I'll hop in the beetle and wind it out. I also don't want carburetors for three reasons: added noise, expense, fiddly tuning (that last one might be my imagination.) I know once I get the CIS dialed in, it should be very reliable for a good long time. Do I want an angry, ripping-exhaust 911 to tear around back roads? You bet, but I don't have space or money for another one, so choices must be made.

I know the CIS doesn't lend itself to performance tuning all that well. But it would be foolish not to do a little tuning during the rebuild while I have the opportunity. That said, I'd probably be just fine with a fresh, totally stock 3.0.

So are there any downsides to my plan? Or things I could also do that would make sense while I'm in there?

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9.8:1 is pushing it unless you can reliably get 93 octane. 9.5:1 might be a little safer with little downside in power.

Overall it looks like a very good plan for a robust CIS engine.

Rebuilt heads are a good thing. I'd expect new guides and valves. Likely the valve stems are worn too, so don't be surprised if the shop recommends new valves.

are getting the cylinders relined and the JE's a better value, less expensive than a new set of mahle CIS euro P&Cs?

Sounds good. Very similar to my rebuild. Currently ongoing. With a few minor differences. The JE pistons come in 9.5:1 which is what I got. A slight increase over stock but not as high as euros.


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Maybe 9.8 was a typo. Got this info from EBS. I bet it's supposed to be 9.5.

So far, yes, by about 1k.

Why not 3,2 with 98mm P&C, if you need the cylinders redone?

Too bad you don't have the large port motor.

Because you can't do that with the 3.0 cylinders. You need to buy a set of 3.2 cylinders and have them bored out. Cost just went way up. I looked into this option for my 3.0 and decided it wasn't worth the extra cost.

There are bored 3,0 cylinders available. At least there was a while back when I checked.

Apparently they can be prone to cracking, in some applications.

I found that it wasn't that much more expensive to go 3,2 IF you needed cylinders anyway. I have Mahles so I lucked out on my rebuild. But then again, a 3,2 does sound cool.

To the OP. Count the fins on the bottom of the cylinders, that will give you an idea of what to expect.

Yeah, I don't want to bump up to 3.2 because of the extra cost. My philosophy here is to add performance where it makes practical and financial sense. My heat exchangers are shot, might as go SSI and save a few bucks over OE, performance gain is a bonus. That sort of thing.

I was told that I could run 9.8:1 on 91 octane. What are the possible downsides? Do I need to recurve my distributor if I go with this CR and 964 cams?

I think this is basically Wayne's Upgraded 3.0 CIS from the rebuild book.

9.8 to one should be doable on 91 octane. Hope so, since that is what my almost done motor will have.

The 83 distributors rely on vacuum for much of their advance, and retard, which is primarily for smog reasons.
I'm not sure what needs to be done to your distributor for your application.
The 78 and 79 distributors only have vacuum for advance and have more centrifugal advance built in. I have heard that those are the way to go with the vacuum disabled. However the 83 CIS has controls that the 78 CIS doesn't.

Supposedly there are old threads outlining what to do to make CIS perform better.

In my research I've found that people with stock cis had issues running the euro compression. One guy I spoke to said he probably would not do it again if he had the chance. He keeps extra pistons on the shelf due to detonation. Also if you are going with JE,s they come in 9.5:1.

On the distributor I was told by one rebuilder he doesn't recommend a recurve for cis engines.


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Hmmm. Definitely things to consider. I think the biggest fear I have with making modifications is that I'll be dissapointed with the performance. Swapping out pistons in a year doesn't trip my trigger. I've only driven the car 7000 miles, so a healthy 3.0 running sweetly will probably feel pretty great.

Stock rebuild with SSI's and a 2/1 muffler will work wonders.
Throw an efi system on it later to really wake it up.
Works for me. :)

Hi- I think Matt may be talking about me. If you can muddle through the fuzzy pictures, I saved these from another thread. This is my exact experience with the euro pistons. Some people have 930/10 engines running just fine with them so YMMV.
I honestly do not think it's detonation. I believe without any kind of scientific evidence that there is something wrong with the manufacture of these pistons.
I do have extras I'd be happy to sell :) My car has JE 9.5's now.



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Interesting article. A little scary too. Do you know what issue this came from?

I removed the last three cylinders and pistons yesterday. No surprises and they all came out pretty easily.

I did learn that one has to support the chain while rotating the engine, and its sort of a three-hand task with the case on its side. I turned everything extremely gently though.

I feel like I pretty much have to open the case though. There is simply no way I have any confidence that some carbon from the tops of the pistons have not fallen into the case, not to mention some of the other little bits of debris that I didn't clean off the case before opening (bonehead move, I know.) How does one do a top end without risk of contamination in there?

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Other than the worry of resealing the case there is really no good reason not to do it at this point.


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I work from home, so I'm able to snatch moments here and there to work on the engine. Today I got the case apart. Nothing really fought me, although some of the acorn nuts were a bit stubborn and creaky. Everything came apart just fine. Here's some pics. I have to say, I'm in the groove at this point, and enjoying the process. I know that once I'm done (barring any serious mistakes) I'll have an engine that I can drive without worry and that I know went together the right way. And that right there seems like a mighty good feeling for the long haul. I sent my cams and rockers off for regrinding today, I'm going with the 964 grind.

So here's the pics. I have not really evaluated any of this yet. Just as a reminder, engine has 117k miles and to my knowledge has never been apart.

One of my ramps broke when I removed the bolts. You can see the broken pieces in the bottom of the case.

Some random pics of the left side of the case bearings. I have not pulled the crank out yet. I see some copper coming through on some of the bearings.

One thing that I didn't expect. The inside of the case looks incredibly clean. When I rebuilt my aircooled Type 1 engine last year I spent half a day cleaning sludge from the inside of the case, especially at the bottom. And that was after I had it "professionally" cleaned. The bottom of this case looks brand spanking new. Is that normal?


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It would seem so, that the engine cases are pretty clean. Mine at 133k looked similar. Bearings looked the same too. I had a little more golden sheen on the cases, above the "oil line".

I think regular oil changes helps, but maybe it's due to the dry sump. The oil that leaks back after sitting a while is coming from the tank which will be cooler.

I would imagine the nature of the Porsche design is to get the heat out of the engine quickly, thus limiting the amount of coking and sludge.