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3.0 204hp Euro Engine Rebuild

 

When I purchased the car, I did it knowing the engine was in need of a rebuild. After the engine strip down, examination of the crank shaft revealed a deepscore where the #6 big end bearing had disentigrated, which turned out to be the reason for the rebuild. The bearing had worn paper thin and was "grabbing" the crank. Machining the crank was attemped but the damage was too great. With 911 crankshafts, once the hardened outer surface is penitrated, the metal becomes very soft. This necessitated the sourced a second hand crank shaft. Examination of the other dismanted parts revealed that 2 pistons had cracked shirts (see pic below), and another one was under weight. To do the job properly meant replacing all pistons and barrells. Crack testing also revealed one of the conrods needed replacement.

If your 911 motor has suffered a similar fate, particularly with a main bearing, I would love to hear the details - email me your story.

dismantled 3 litre engine

First tasks after purchasing the car was to join the Rennlist 911 email list, pick up a copy of Bruce Andersons "911 Performance Handbook" and Bentleys "Porsche 911SC Workshop manual". These resources gave me a lot of information and aided my rapid P car learning curve. In trying to resolve my Piston sourcing problem (3 of them to be precise), I uncovered varying opinions on whether it was wise to purchase second hand replacements or to lash out and purchase a new piston / barrel set. I spoke to as many people as I could and researched all the books I could find. The weight of opinion seemed to suggest that if I intend keeping the car, the job should be done properly with a new piston / barrel set being installed. Fortunately I had budgeted for a new set when purchasing the car.

My "educational" continued as I scaled the internet and text books for detailed information on rebuilding a 911 engine. Whilst I had rebuilt a number conventional 4, 6 & 8 cylinder engines over the years, the air cooled flat six was going to be a real challenge. Except for a few pictures, unfortunately I found very little of useful material on the internet. Unfortunately th Wayne Dempsey book had not been printed at that time.

In dismantling the engine I was carefull in sorting and labelling the parts, using zip lock bags and plastic containers.

It wasn't until a week later that I discovered that the second hand crankshaft had come from a 78-80 model 3 litre motor, which was slightly different to my '81 crank in that it used a different flywheel spindle bearing setup. Not a major problem except I needed to find a machine shop that would take on drilling three screw holes in the end of the crank. With the help of my local Porsche Mechanic this was completed with only minor drama. I also had my Mechanic swap over the distributor and half shaft gears, which would have been a pain to do without the proper tools.

Shopping list so far includes:

  • crank shaft (used)
  • conrod (used)
  • Mahle piston / barrel / ring set (new)
  • full gasket / seal set
  • #8 nose bearing
  • main bearings
  • big end bearings
  • wrist pin set
  • counter shaft bearings
  • timing chains and guides
  • oil pressure switch
  • bolts (rod & flywheel)
  • valves and guides
  • pop-off valve kit

Look at that #6 big end - beyond repair

Two cracked Piston skirts

Shiny new Mahle piston / barrel set

6 revived heads

In preparation for the assembly of the crankcase, I had great difficulty in sourcing a tube of Loctite 574. Loctite Australia informed be they didn't sell Loctite 574, but they suggested using Loctite 515 which was a very similar product. However a number of Porsche people advised me not to use it. The local Porsche dealer could provide a Porsche badged version for $75 which sounded ridiculous to me. My local Porsche repairer was able to source a bottle of Wurth Case Sealant at a reasonable price. Apparently Wurth produce the Loctite product under license. I also purchased a tube of Loctite #3 as a non hardening sealant for use with o-rings, and a spay can of Engine Assembly Lube which made it easy to squirt lube into difficult places to get to.

Next stop was to visit the local machine shop for a number of reasons: 1) to have the con rods balanced, 2) have the rod pins pressed in and machined to suit the new piston pins. Unfortunately the second hand rod I purchased was quite a bit lighter than the original set, which required having the other five rods shaved to match the weight grouping.

Layshaft and oil pump installed

Crankshaft and rods ready to go

Crank and rods installed in case

Whilst all this activity was going on, I sand blasted all of the tin ware and applied numberous coats of heat treated black paint. I also rubbed down the cooling fan and shroud and beautified these with a combination of gold and red paint.

Sealing the case halves

Case halves bolted together

The barrels going on

Putting the wrist pins on - use plenty of rags to block the holes - you don't want to drop anything inside the case

One timing chain case on

Cam towers on

Assembly of the crankshaft and rods went without a hitch. I found that bolting the flywheel to the crank and standing the crank up on its end using the flywheel as a base made the assembly very easy. The next task of assembling the crankcase was also uneventful although I found it challenge to get the through bolts and case nuts on and tensioned quickly before the sealent went "off". Performing this task alone, I found it easier to suspend the upper case half from my engine host and then lower it with the 3 upper con rods being held upwards with plastic coated wire. The extra "arm" made it a lot easier.

The pistons and barrels went on next. There are a number of ways the pistons and barrels can go on, but I chose to assemble the pistons, rings and barrels on the work bench, with the piston pushed down the barrel with the pin holes exposed at the bottom. It was a relatively simple task the then align the pistons in the correct direction and insert the rod pin and clips. Ensure that you stuff plenty of rag down all of the open holes in the case, as anything that drops down there will be a real pain to get out.

The next snag came when installing the cooling tinware around the barrels, as I couldn't remember which way around they went (the cut out section up or down). None of the reference books where much help, a quick email to rennlist solved the issue. The inner tins are installed with the cut out section facing the head side of the barrel.

Cam timing set

Use Mercedes "torque convertor sump plugs" to block the air pump holes near the exhaust outlets

Near complete long engine

Modified el cheapo engine stand

 

 

I dispensed with the factory air pump and injection system, and plugged the injector holes in the heads with a Mercedes Benz "Torque Converter Sump Plug". This is an Allen keyed plug that fits perfectly.

Next went on the cam towers, cam shafts, chains and tensioners. Not having the special tools for torqueing the cams shaft nuts, I took the motor for a quick trailor ride to my Porsche Mechanic to check my timing and tension the nuts.

The rest of the build was uneventful, however assembling the motor in my spare time, the rebuild seemed to drag on for ever. "Slow but thorough" sounds appropriate.

Installing the wiring to the back of the alternator

Shroud and tinware goes on

Front on shot with new fan colours

Complete engine

Complete engine on stand

Fitting transaxle with the help of an engine crane

Ready to re-install

Rear of car 35" off the ground

Under she goes - using the engine stand base as a trolley

 

 

 

 

For another view of engine remove and install, see here http://www.paulsgarageblog.com/how-to-remove-the-engine-and-transmission-from-a-porsche-911sc/

Many of the photos taken during my re-build and featured on this page have now been published in Adrian Steather's book, "Porsche 911sc, The Essential Companion".

The book can be purchased at Veloce_Publishing, Amazon or any good Motoring book shop.

I hope your are enjoying this site and have found what you are looking for.

I am a Porsche enthusist with no Commercial connections, sharing what I have learnt.

This website comes at a cost to host and maintain, and you will appreciate not enduring pop-ups and advertisments. Any donation you can make will assist in the ongoing upkeep, and will be sincerely appreciated.


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Disclaimer : This site was designed and produced solely by the author, and is not associated with Porsche in any manner, except for a mutual appreciation and love of the cars. All pictures and references to the Porsche name, and the car names and shapes are for restoration reference only, and do not imply any association with PCNA. Information and technical articles within this website are for reference only. Consult authorized factory manuals when performing repair procedures. By entering this site, you agree to hold the author free from any liability arising out of the use of any information contained within.