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.

I'm making slow but steady progress on the rebuild. I try to get at least a couple hours in every day before and after work. I mostly daydream about how far I could get if I had week stretch of free time!

Here's the status on some parts after evaluation.

Case/Cam housings: Good, I'll be putting new standard bearings in
Crank: Good. Measured up just fine, journals look good.
Cams: At Dougherty's getting ground to 964, rockers and shafts getting refreshed too
Heads: At Ollie's, not sure what they need yet
Pistons: Ordered new 9.5:1 JE's from EBS. I decided to play it safe and not go with 9.8:1.
Cylinders: Replating with Nikasil through EBS
Rods: on their way to Ollie's for a rebush
Distributor: There's like 1mm of end play, so I'll be sending that out too.

Meanwhile, lots of cleaning going on. I used my Harbor Freight coupon and picked up the blast cabinet. Had my 13-year old nephew George assemble it according to the Alvarez Youtube videos. Good info, but pretty tedious to watch. It helps to set the player on 1.5 speed. I also sprung for the Tacoma kit right away. Domino effect means I need a new compressor now too. My 20 gallon 4hp lasts maybe 1 minute before it gets winded. Always wanted a blast cabinet, and I should have found one long ago. This thing is fantastic. It's a great motivator to get nice clean parts right off the bat.

My Harbor Freight engine stand was also giving me nightmares. My yoke is a really loose fit and all I could imagine were the welds failing in the middle of the night. It was good enough for my VW engine, but this is quite a bit heavier. So I fabricated a 3/8" thick metal bracket that bolts to my woodworking bench. The bench is made from solid oak, 5" thick solid slab top, and weighs around 500 pounds. I tested the whole arrangement by lifting myself off the ground (I'm about 250lbs.) and bouncing up and down on the yoke. Solid as a rock.

Now that I've got a place to mount the case I can get busy on the fun task of cleaning.



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If you are concerned about your CR you should check what CR the JE pistons actually give you.

In my case, the actual CR I obtained from the JE 9.5s was about 9.8 to 1. All other aspects of my SC motor are stock and in spec. My heads CC'd out at 89cc, with 90 being the stated number. The pistons measured as stated in the JE specs. I used one .25mm cylinder base gasket.

Huh. Interesting. So I assume you were okay with the higher compression then. Why didn't you use thicker base shims to lower the CR?

I was actually hoping to get more than 9.5 and I have read that 9.8 is dueable on pump gas with a 95mm bore. My deck height is about 1mm, so I think I am good to go.

4 hours in on cleaning the case. So far so good.


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The case is clean and ready for reassembly. I've got probably 20 hours in this. Seems about right according to the book. There is still some discoloration here and there, especially at the top of the case. I can understand the temptation to polish it all up, but the important thing is that its clean, right? I didn't want to use any abrasives on the case, just coarse rags, orange degreaser, brass brushes, carb and brake cleaner. My piston squirters were all free and spraying cleaner after the first soak.

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Unless the table is bolted to the floor you're not going to be stable to build out
Bruce

The only way I see that working is if this guy has that mounted to something like a 500 pound French Roubo woodworking bench made out of oak. Otherwise, I agree.

Wow
 

What compressor did you upgrade to? I have a 4 hp with 2 20 gallon tanks in series, and it isn't enough to blast.

We'll see. It's a massively heavy bench, but I've already planned to add an outrigger/leg if need be. Thanks for watching out for me.

I didn't yet. Still using the 4hp 20 gallon. I get maybe 1 minute of blasting. Lately its been blast for a minute, clean for 10, blast for 1, rinse and repeat. Just been waiting for a sweet deal on a compressor to pull the trigger.

Deck Height and quench
 

So I've made a bit of progress on this rebuild. Got all my parts back from Ollies, EBS and John Dougherty and I've got the short block together. Here's a couple pics.

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I've also CC'd my heads and piston domes. Here's where I'm running into a bit of a quandry.

The plan was to build Wayne's Upgraded 3.0 CIS engine. So I had my cams reground to 964 profile by Dougherty and I bought 9.5:1 JE pistons to mate up with my original cylinders plated with Nikasil by US Chrome through EBS. Heads and rods were rebuilt by Ollies. Bottom end got cleaned and new bearings, crank just got cleaned.

The cylinders were not remachined on their ends, just blasted, so their height is the same as before. Group 6.

Head-cylinder mating surface was cleaned up by Ollies, it doesn't look like they took much off, perhaps a thou or two just to clean up (just guessing, there wasn't a number on the invoice) They all measure .095" from surface A to B. I couldn't find a spec on this measurement. Any idea what this should be?

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I cc'd my heads and piston domes with the oversight of Lee Schlabaugh of Stalltek. Lee has been my mentor through this whole process and I would be lost without him. So I'm confident my numbers here are correct. Lee also ran some theoretical numbers for me but this was before we had a deck height measurement.

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So yesterday I finally had a chance to measure my deck height on #1. Here's what I came up with:

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Bore: 95mm
Stroke: 70.4mm
Deck height to flat: 0.80mm (measured off cylinder top at TDC down to flat at perimeter of piston)
Quench: 1.90mm (measured with clay at left/right edges of piston)
V1 Swept volume: 499cc
V2 Deck height volume: 5.76cc (using 0.80mm deck height)
V3 Cyl. head volume: 89.2cc
V4 Piston dome volume: 39.5cc

Deck height and quench measured with NO copper gasket or shim at base of cylinder. My Victor Reinz gasket set (I'm also using the Wrightwood racing set for the viton parts) did not come with copper base shims, but rather these black colored shims that seem to be made from aluminum? They are .30mm thick.

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Using Bruce Andersons formulas I came up with 9.99:1 CR. My goal is 9.5:1 CR, and those are the pistons I spec'd when I ordered from EBS. I don't know how verify if I got the right pistons or not. There is no dome volume listed on the spec sheet.

Here's where I'm a bit confused. Which deck height number to use? Because when I measure to the lip off the cylinder head I get .80mm, but when using the clay I get 1.9mm. Wayne calls the clay method "deck height" so which number should I be using?

Aside from that, it looks like my compression ratio is too high, and my quench is also too large. So I've got the worst situation. Can someone explain how, especially with no shim under the cylinder, that my quench is almost 2mm? If anything, it should be too tight, given that my heads have been machined (albeit perhaps slightly). I don't understand how the quench space can be reduced by half a millimeter (sounds like I should be around 1.5mm) without machining a bunch off the head. That's also going to increase my compression ratio, when I need to go the opposite direction. Then I would need to machine some off the top of the pistons to open up the combustion chamber.

I'm just not sure how I could be so far off on quench (especially without base shim/gasket) and still end up with a higher compression ratio? I would think if the compression ratio were that high, that my quench would also be either right on, or too close.

I'm a bit paranoid about running anything over 9.5:1 for fear of detonation. I want this to be a long lasting engine.

Nice writeup. Looks like you are covering all the bases.

I just went through this myself, a couple of things, I discovered.

Those base gaskets are probably copper, just with some coating.

I bet if if you re-measure your deck height with the gaskets you will be close with the deck height you want. My deck was identical to yours with out the gaskets.

My heads also measured out at 89cc giving me a CR of ~9.8 to 1 with one .25mm base gasket, which is what I wanted.

In your case going to a .5 base gasket will probably give you the 9.5 CR you want.

To answer your question, you are measureing the deck height correctly, at the edge of the piston. However the clearance at the side of the dome will be something like 2mm.
Keep up the good work.

Thanks Gordon. I read some of your posts about your build. I'm going to scratch off a little of the coating and see what lies beneath.

Are you not worried about detonation with the 9.8:1 CR coupled with the 2mm quench? I was under the impression that we want the combustion gasses to get squeezed out of the perimeter (the dome portion of the piston) and swirled around, and that a larger space here promotes detonation. Quench or squish should be between 1 and 1.5mm. But I'm no expert. Just mimicing what I've read in Wayne and Bruce's book.

What octane are you running? Single plug?

What nozzle are you using in your blast cabinet ? Havnt seen that one before. I needed some more air in my shop so I bought a large tank off craigslist then a 17cfm compressor pump from hf for $160. Good luck with your build!

Call Mike at the Tacoma Co. I bought the upgrade kit from him for the Harbor Freight cabinet.

I'm running single plug with Weber 40s.

I don't believe there is much difference in 1 or a 2mm clearance between the dome and head as far a squish and quench. I don't know if it is possible to get 1mm dome to head with these pistons without the edges hitting. From what I know the squish and quench is more of an issue with bathtub design heads? Porsche used the shape of the piston in their SC and Carrera motors to achieve a swirl for more complete combustion. Maybe others with more expertise will chime in.

The deck height, as measured on our motors, is more of a piston to head clearance for safety issue. Generally 1mm. Although some have run less(.8mm) with out problems.

As far as my CR and detonation goes, yes that can be a cause for concern since I am using 91 octane fuel. My thinking is that the original S motor ran 9.8 to 1 CR with carbs and an old school cam that has quite a bit of overlap. My motor follows that same philosophy. The key, for me is to be conservative with my ignition advance curve.

Here was my piston to head clearance being measured.
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The black lines are the "deck height".

Great info Gordon. I ducked out to my shop early this morning and had another go at measuring. This time I took twice as long and made sure all my ducks were in a row. I had some errors before.

I used the .012"/ 0.30mm copper gasket at the cylinder base. Scratched off a little of the black coating to verify it is indeed copper.

Starting with a little more clay I did two rounds and got two close numbers which averaged out to 1.74mm. That's more like it.

I also measured down to the groove again several times, both at TDC and while rocking the crank, letting the piston raise the caliper stem until it reached TDC. Both times, and both sides I got within a couple thou of 0.046"/ 1.16mm, so that's the number I stuck with.

So 1.16mm translates to 8.22cc deck height volume (at 95mm bore)

So here's what I ended up with.
Head Volume: 89.2
- Piston Dome Volume: 39.5
+ deck height volume 8.22
=Combustion Volume: 57.92
+ Swept Volume 499
=556.92
/ Combustion volume 57.92
= 9.6:1 Compression Ratio

My largest head volume is 89.8cc which makes 9.5:1 CR

Bruce/Wayne says they should all be within .1 of each other, so looks like I'm pretty much there.

Great. Looks like you are ready to get it together.