3.2 Top End Overhaul – A Success Story

[dkirk]

At 112,000 miles, my ’88 911 coupe had started to blow some blue smoke on startup, consume more oil than I thought normal, and made more valvetrain noise than other 911’s. Due to the known valve guide and stem wear issues that the 3.2 series engine is noted for, I knew it was time for a top-end overhaul. The clutch was also getting more difficult to disengage with unusually high petal force. Armed with the knowledge that the Bentley manual and Wayne Dempsey’s book imparted, plus the car lift in my friend’s well-equipped shop, I tackled the job this spring.

Powertrain removal was very straightforward. A wooden support stand, previously fabricated by a friend, was invaluable for supporting the powertrain as the car was lifted from it. A thorough pressure washing was then performed to degrease the externals as much as possible. As evidenced by the fasteners, cable ties, and other tell-tale indicators, this was the first time the engine had been removed from the car since it left the factory. After separating the engine and gearbox, the original equipment, rubber-centered clutch disc confirmed this. On disassembling the throwout bearing fork from the support shaft, it was evident that the needle roller bearings were dry of grease and wearing into the shaft, causing the high clutch petal force.

With the engine and gearbox now separated, engine disassembly then began. No surprises were encountered, other than breaking an exhaust stud when trying to remove one of those socket head nuts. Penetrating oil was a big help here.

The engine was disassembled down to the crankcase, which was not split. All rods felt “right” with their respective crankpin bearing clearances and the engine was remarkably clean inside, so I elected to perform just the top end rebuild as planned. All 24 cylinder studs were removed and replaced with steel ones – a good practice after 23 years and many thermal cycles. Cylinder air baffles were blasted and repainted and the engine crankcase was thoroughly cleaned externally using spray degreaser and a wire brush.



I was somewhat disheartened to find that my engine was equipped with Kolben-Schmidt, Alusil cylinders…I was hoping for Mahle. The cylinder bores all appeared uniform and in excellent condition, with cross-hatch still evident. Piston skirts were just as nice. Measuring a top compression ring end gap, I was happily surprised to find that the clearance was right in the middle of the tolerance band! This is remarkable – an air-cooled engine with this many miles exhibiting virtually no ring wear. No need to replace rings on this overhaul.

With heads removed and on my workbench, it was obvious that oil was getting into the combustion chambers as evidenced from the soft, wet appearing carbon.



I had decided to send heads out for reconditioning and I selected Anchor Atlantic Enterprises LLC to do the work, based on their excellent reputation. Before boxing up, I used a hand grinder to match and blend the inlet ports to the thermal isolator blocks plus smooth out a few casting imperfections.

I had purchased some 964 camshafts from a reputable eBay seller and had to modify the right-side camshaft to fit the 930 housing. This involves cutting off the power steering drive extension as shown:



While the heads were being refurbished, all external surfaces of the cam chain housings and cam tower housings were fastidiously cleaned with a wire brush and degreaser. All gasketed surfaces were carefully scraped with a razor blade and wire brushed to restore unblemished surfaces. The pan sheet metal was bead blasted and repainted semi-gloss black. This all took an inordinate amount of time, but was worth it.

When the heads arrived from Anchor Atlantic, they were carefully unwrapped and examined. Heads had been ultrasonically cleaned, bead blasted, all new bronze guides, all new valves, new stem seals, 3 angle valve seat recut, spring forces checked, sealing surfaces machined, and inserts installed in all exhaust stud holes. It was like getting brand new heads! Best $1300.00 I’ve ever spent! I highly recommend them - Anchor Atlantic Enterprises LLC - Home.





Now reassembly could begin in earnest. With cylinders and heads fitted, cam housings were appropriately coated with LocTite sealant, assembled to the heads and torqued to spec. Then head stud nuts were lubricated and torqued to initial value, then the 90 degree turn as specified in the Bentley manual. This approach yields more consistent preload on each stud.





Cam chain housings were now refitted and torqued to spec.



The 964 camshafts were lightly oiled and inserted into the cam housings. Both rotated freely indicating no distortion of the housings took place during the torque sequence. Cam sprockets, chains and tensioners were assembled. No parts replacements required in this area as all components appeared in like-new condition. Per the book, the rocker arms and shafts for cylinders 1 and 4 were then installed and shaft lock bolts torqued to spec. This difficult job was made easier by using a ¼ in drive torque wrench with some Allen bits shortened such that ample tool clearance was just attainable. Cam timing was then set to IO of 1.24 mm @ TDC with lash set at .1 mm. Then the remainder of rockers and shafts were carefully installed and valve lash carefully set on the remaining cylinders (so I thought).

[dkirk]

The beautiful Roush & Spigel billet aluminum oil return tubes were reused (previously installed). I eliminated the external snap ring in favor of some Aeroquip thumb screw hose clamps as these don’t damage the machined surface of the tubes.



All paper gaskets were coated with Dow Corning Silicone Grease during installation. This is not for the purpose of reusing gaskets in the future, but to prevent sticking gaskets and scraping of surfaces which takes so much time to get clean. I’ve used this technique on other, small air-cooled engines with much success. And it works perfectly on Porsche valve cover gaskets.



Now components on the upper half could be bolted into place. I had previously matched the intake manifold runners to the thermal isolators using the hand grinder. The throttle body was also matched to the manifold…the factory had done an admirable job but there were a few areas that needed a finishing touch. Some general smoothing and blending of interior surfaces was also done on each manifold half. After a thorough cleaning, manifolds were then bolted to the heads using LocTite 263 (blue) on the manifold stud nuts, hopefully to prevent the notorious “backing off” torque relaxation that occurs, causing air leaks. With the distributor properly timed (I thought) and fan installed, it’s starting to look like a 911 engine again.



Now it was time to roll her over and get the exhaust components installed. Exhaust system was installed using all stainless hex nuts and washers wherever possible. Plenty of NeverSeize grease was used on the threads to prevent potential galling. A stainless test pipe replaces the catalytic converter. And my new Dansk sport muffler bolts in place perfectly. Note that I forgot the steel oil line – this will come back to bite me later.



Now to the lovely G-50 gearbox…the old throwout bearing fork support components were replaced by a new Roush & Spigel assembly, available through Pelican. In this kit, needle bearings are replaced by oilite bronze bushings (which should have been fitted originally). A new shaft is also supplied. The new components are shown assembled below:



Naturally, a new Fictel & Sachs pressure plate, spring-center clutch disc, throwout bearing, and pilot shaft bearing were installed at this time. My savings account was exponentially decreasing at an alarming rate.



Now the engine and gearbox could be mated and the whole power unit transferred to the engine support stand. As the stand is on urethane casters, it easily rolls in place under the car for powertrain implant.



It was about a 3-hour job to get the engine fully reinstalled and everything hooked back up. Forgetting the hard oil line now bit me – had to loosen and remove the LH exhaust manifold to get the line installed, wasting about 45 minutes.



With everything hooked back up and oil in the tank, the first start was attempted. All did not go well – after 6 cranking attempts without even one combustion event occurring, something was obviously wrong. The good side of this was that oil pressure was attained and engine was nicely prelubed. After checking all the obvious, it was time to quit for the night. Next morning I pulled the LH lower valve cover and distributor cap and found that the crankshaft was 360 degrees out of position relative to the distributor – a common mistake for amateurs. With this embarrassing mistake fixed, the engine fired right up on the next attempt. Most noticeable was a loud clicking sound emanating from the left bank – I immediately suspected a tensioner was not right and the engine would have to be pulled again. After the panic subsided, listening with a stethoscope pinpointed the problem to be #3 cylinder. Off with the valve covers and found that lash on both inlet and exhaust was around .020 instead of .004 inch. I must have had the cams in the wrong position when setting this…strike 2 on embarrassing mistakes. I’m not as good of a “wrench” as I thought I was.

With all this adjusted properly, the engine started and sounded very proper. Occasional blue puffs of blue smoke gradually subsided as the excess build-up oil burned off. I drove it home 6 weeks after the project began. During the 30 mile drive home, I kept feeling like the engine was going to cut-out and die at any moment…but it never did. Matter of fact, it ran and sounded better than it ever had. Throttle response was noticeably improved. After the oil was up to temp, a couple of WOT acceleration bursts confirmed that this thing really runs well!

I now have around 600 miles on my top-end-overhauled engine and it runs like a fine German Coo-Coo clock (Swiss watch doesn’t apply here). Engine is smooth, sounds great, and after 3700 rpm, pulls like a freight train. The 964 cams have given it a more sporting personality which I like, and they seem to compliment the Steve Wong chip previously installed. I’m also proud to report that there is not one spot of oil on the garage floor!



This was the first 911 engine I’ve ever worked on. It is the engine that is the main attraction for me in owning a 911. A bit dated by today’s standards, it is nevertheless a first-class example of high-performance, air-cooled engine art. I’ve never worked on a more intricate, complex, yet beautiful engine – truly a masterfully designed piece of machinery. The project was almost as enjoyable to me as driving the car! And now that I know what my engine looks like inside, I can think about all those nice parts rotating and reciprocating in synchronized precision as I listen to its wonderful voice as it effortlessly spools up through the gears.

Thanks to everyone on this forum who answered my questions in times of mental anguish and panic…greatly appreciated! Your experience was of great assistance and a confidence-builder for my amateur Porsche engine ranking.

[hcoles]

good going, much faster than I was, I also ran into the unexpected bank account drain rate, but I did all the while you are in theres, and then pulled motor two more times in the next few years to do more, e.g. fuel lines, redo clutch fork bushing with a custom design

[carrera88]

Awesome Dave,
Where can I find that air cleaner? Not K & N.

[dkirk]

carrera88,

Air filter and adaptor is available through Pelican. Brand is AireTEK and the part number is PEL-INTK911. Cost is $195.00. It is a nice piece - seems to be less restrictive than stock and produces a sweet induction note when the throttle is opened.

[Eagledriver]

Excellent report, congratulations. One suggestion, when you do your next couple of valve adjustments check the headstud torque. My steel studs got loose on a couple of heads. They torqed right up and after a couple of years they no longer loosen.

-Andy

[glewis80SC]

Great write up thanks for sharing.

[AlfonsoR]

Really good write up and thanks for the silicone grease tip. How long did you ponder the dual-spark question..hehehe. I need to do a rebuild on my engine and will follow a very similar path. Hope it goes as well as yours.

Guards is #1

[hcoles]

great job, a tribute to the DIY'ers, it can be done and done with high quality by a DIY but I suspect this is not the first wrench you have turned.

[dkirk]

Thanks guys, for your kind words. Andy - great suggestion on checking head stud nut torques...will do.

Engine now has about 1500 miles on it and is running better than ever. Still not one drop of oil on the garage floor after sitting. New gaskets and o-rings really pay off. Oil consumption in this time has been less than 1/2 quart.

My good friend has a 911 coupe and our cars are only 19 VIN numbers apart. His car has a tad over 50,000 original miles and is in excellent condition. Our engines are similarly equipped - but he has a B&B exhaust system where I now have the 964 cams. My car now has the performance edge, especially noticeable in 2nd gear. But my bragging rights may be short lived - he was so upset that he bought a set of Web Cams and we installed them last weekend. We haven't raced yet, but I'm thinking he may now be top dog again...we'll see.

[whiz05403]

Hello, thanks for the great write-up. I am planning on doing the same thing including the clutch. Do you mind giving a ballpark figure on how much this will cost me. I hope to do all the work myself like you did excluding the machine work. Also, what special tools did you purchase? Thanks.

[hcoles]

Originally Posted by whiz05403

Hello, thanks for the great write-up. I am planning on doing the same thing including the clutch. Do you mind giving a ballpark figure on how much this will cost me. I hope to do all the work myself like you did excluding the machine work. Also, what special tools did you purchase? Thanks.

There are probably part lists somewhere here and you might be able to borrow the special tools needed, not too many required. If you do all the "while you are in there" the parts add up. E.g. all the clutch parts and such things as engine tin seal. It is better not to know how much it will cost. If the p's and c's are good that helps significantly. We'll assume the bottom end is good. A lot of people here feel that if you get that far, might as well open the bottom and do the standard checking and replacing as found. I didn't do that but only had 75k miles, I probably should have anyway but I was nervous enough as it was.

[dkirk]

Whiz05403,

Here is the parts breakdown:

Clutch kit 911CP-2003BN $1,079.50 1 $1,079.50
Guide Tube 950-116-813-06-M260 $72.75 1 $72.75
Clutch align tool PEL-TOL-CA3 $8.85 1 $8.85
Shaft/bushing kit 10-1518-090-M157 $158.25 1 $158.25
Flywheel pilot bearing 931-102-111-00-M34 $6.50 1 $6.50
Cylinder head exhaust studs 999-062-239-02-M58 $4.00 12 $48.00
Cylinder Head Studs 10-0115-101-M105 $11.75 24 $282.00
Dansk sport muffler 10-1010-157-M350 $487.25 1 $487.25
Piston ring set 930-103-986-00-M42 $24.75 2 $49.50
Chain ramp 911-105-222-06-M114 $6.75 1 $6.75
Oil cooler thermostat 930-107-765-00-M322 $157.50 1 $157.50
Intake insulator 930-110-459-00 $6.50 6 $39.00
Shift coupler boot 950-424-294-06-OEM $16.00 1 $16.00
Gasket set H-100-907-04KTN $290.50 1 $290.50
Stainless ex syst. Nuts & Washers Misc Hardware $14.56 1 $14.56
Misc Hardware Misc Hardware $18.29 1 $18.29
Flywheel ring gear 950-116-143-01-M260 $140.50 1 $140.50

Anchor Atlantic Cyl Hd Recond $1,318.72 1 $1,318.72

Total $4,194.42

This was a copy-paste from an Excel spreadsheet so I hope the colums line up. Total cost was right at $4200.00 for all the parts which were purchased through Pelican. Not shown are the special tools which consisted of the camshaft sprocket holding tool, dial indicator holder, and engine stand adaptor. Figure an extra $200 for these.

Reason I didn't split the case was due to the following logic:
1 - Oil pressure was right to spec values
2 - Engine oil remained clean between changes with no metal detected
3 - Upon teardown, interior of engine was very clean
4 - Rod bearing clearances were all consistent (tested by "feel" but qualified by experience)
5 - An additional $1000.00 would have been added to the bill for replacing bearings and rod bolts. My budget for the project didn't allow it. It's a street engine and not driven hard.

Believe me, it's worth the money to have an engine that really performs well and runs reliably. And the satisfaction of doing it yourself is priceless.

[Montanaro]

Thanks for sharing your rebuild and pictures - great job.

I noticed the return tubes - do you or anyone know where you can get these and the approximate cost? Any one have experience positive/negative with them?

Thanks,
David

[whiz05403]

dKirk,

Thank you very much for the cost breakdown. Looks like I need to allocate more money from my paycheck to my "secret" account!!

I hope I can pull it off as well as you did.

Mike

[dkirk]

Mike,

Happy to help. The "secret" account is a must for something like this.

I can't top you on any of those airplanes that you're qualified in. However, I do have 20 minutes stick time in the Spirit of St. Louis replica, built and owned by the EAA. Unstable in all axis, but a true blast to fly.

Best of luck on your 911 engine.

Dave

[whiz05403]

Originally Posted by dkirk

Mike,

Happy to help. The "secret" account is a must for something like this.

I can't top you on any of those airplanes that you're qualified in. However, I do have 20 minutes stick time in the Spirit of St. Louis replica, built and owned by the EAA. Unstable in all axis, but a true blast to fly.

Best of luck on your 911 engine.

Dave

Wow, pretty sweet and lucky to get to fly that type of bird!

I still enjoy the A320 but probably miss the F-16 and T-38 the most.

I met a guy who has a Cessna 182 on floats, he and his wife spend every weekend "lake hopping". I was envious almost instantly!!

[wolfrennen]

Great write-up! Thanks for sharing the parts costs with us too!

Originally Posted by dkirk

Whiz05403,

Here is the parts breakdown:

Clutch kit 911CP-2003BN $1,079.50 1 $1,079.50
Guide Tube 950-116-813-06-M260 $72.75 1 $72.75
Clutch align tool PEL-TOL-CA3 $8.85 1 $8.85
Shaft/bushing kit 10-1518-090-M157 $158.25 1 $158.25
Flywheel pilot bearing 931-102-111-00-M34 $6.50 1 $6.50
Cylinder head exhaust studs 999-062-239-02-M58 $4.00 12 $48.00
Cylinder Head Studs 10-0115-101-M105 $11.75 24 $282.00
Dansk sport muffler 10-1010-157-M350 $487.25 1 $487.25
Piston ring set 930-103-986-00-M42 $24.75 2 $49.50
Chain ramp 911-105-222-06-M114 $6.75 1 $6.75
Oil cooler thermostat 930-107-765-00-M322 $157.50 1 $157.50
Intake insulator 930-110-459-00 $6.50 6 $39.00
Shift coupler boot 950-424-294-06-OEM $16.00 1 $16.00
Gasket set H-100-907-04KTN $290.50 1 $290.50
Stainless ex syst. Nuts & Washers Misc Hardware $14.56 1 $14.56
Misc Hardware Misc Hardware $18.29 1 $18.29
Flywheel ring gear 950-116-143-01-M260 $140.50 1 $140.50

Anchor Atlantic Cyl Hd Recond $1,318.72 1 $1,318.72

Total $4,194.42

This was a copy-paste from an Excel spreadsheet so I hope the colums line up. Total cost was right at $4200.00 for all the parts which were purchased through Pelican. Not shown are the special tools which consisted of the camshaft sprocket holding tool, dial indicator holder, and engine stand adaptor. Figure an extra $200 for these.

Reason I didn't split the case was due to the following logic:
1 - Oil pressure was right to spec values
2 - Engine oil remained clean between changes with no metal detected
3 - Upon teardown, interior of engine was very clean
4 - Rod bearing clearances were all consistent (tested by "feel" but qualified by experience)
5 - An additional $1000.00 would have been added to the bill for replacing bearings and rod bolts. My budget for the project didn't allow it. It's a street engine and not driven hard.

Believe me, it's worth the money to have an engine that really performs well and runs reliably. And the satisfaction of doing it yourself is priceless.

[Jeff Alton]

Nicely done, you should be proud!!!

GO enjoy it!

Cheers