How NOT to build a 964 engine.
 

Rennlist is a marvellous place to share our Porsche experiences with fellow enthusiasts, discover some of the hidden details of our cars and even, should the need arrive, learn how best to fix them. Aside from the amazing home vehicle rebuilds and restorations, I'm guessing that the engine build is likely to be the most popular and largest job that enthusiasts & amateurs would consider undertaking. There are many excellent "I built my own engine" threads with rightfully proud owners showing off their work and enjoying the results of their efforts for years to come.

The purpose of this thread is not a celebration, it is to highlight what happens when people do not respect Porsche engineering values and what happens as a result. I'm kicking us all off with some photos from a current 964 engine build, I hope that other members and specialists will follow on with more.....

When sourcing a suitable 964C2 for a project our number one priority is always to find an completely unmolested and accident free donor. These photos from a current job show just that car, purchased by us from a recognised dealer and inspected by an independent specialist before purchase. We were told that it had had a full repaint and recent engine build. Whilst what you will see below is shocking, in our case we are "lucky" because the car is destined for a complete, down to the last nut-and-bolt rebuild, so what we found was of little concern. On reflection, it's a relief that we bought the car and not some unsuspecting punter....


Engine builder Mark started with the top end, immediately finding some "interesting" and liberal use of non-factory sealant:

Clues to the quality of the build were to be found everywhere, including:
Pintle cap not attached to a fuel injector
Alternator wiring hole broken in fan shroud
Knock sensor wire sleeves bonded into fan shroud due to missing grommets (!)
Fan shroud corner broken off
Alternator cowl broken

Clearly someone has taken a lot of care over the previous strip down.

Taking apart the cases revealed a whole lot of fun. Liberal use of yet another sealant was apparent, both on the case joint and on all of the through bolt seals. Evidence that the sealant was already breaking off and causing issues was clear with the build up of waste on the oil pump.

The final job was removing the connecting rods to inspect the big end bearings, a stiff #3 rod gave a hint to what we might find there, but since the car arrived under its own steam we certainly did not expect to find a worn out bearing, loose in the rod. This bearing has been damaged due to foreign bodies in the oil system arriving through the pump, so clearly there is oil system contamination that will have to be addressed.

Thank you Colin.. and Mark...
 

I have always enjoyed your posts. I was always curious about all the "magical" mixes of sealants different builders use..... Looking at the above photos it is evident the old adage that if a little is sufficient, then too much is just right.

Interesting Colin. Thanks for posting.

I'm am amateur DIY type in the process of my first split case reseal. I can't speak for others with similar skill levels but I have spent weeks reading through threads on sealants etc and watching the P fix it DVD over and over again. I work on the engine in 2 hour increments and research each step. I'm using the correct tools. The job will take me months. No one would employ me to do this work as my productivity is low. However, I doubt I would ever be capable of the abomination above.

The reason I'm doing my own reseal is that an OPC full rebuild left me with a nose bearing area oil leak that over time ended up losing 4 litres in 2,000km. It took me three years to work out where the leak was coming from and how it could be fixed. The RTV they put round the leak without me knowing managed to slow it down for a few years. The time to find the source of the leak appears to be their defence. They claim the RTV is standard insurance against leaks in this area.

I haven't found any other extraneous sealant so far but I have noted that they transposed cylinders 1 & 2. Maybe not a hanging offence but not evidence of a careful build. I suppose the point of posting is to point out that I doubt the work in your pics is an amateur enthusiast. More likely a backstreet garage taking on work they clearly didn't understand.

Ai Caramba!!! Why on earth do people take on jobs when they're not prepared to do it well? Seems you guys have caught it just in time before the engine turning into an expensive piece of shrapnel.

And might I add....great having you back on here Colin.

I will never understand why any engine builder would use anything other than Loctite 574 (orange) which Ninemeister have used for over 20 years for every engine build without a hitch. 574 is very easy to apply as a thin bead then spread to an even thickness with a sponge or roller. Furthermore it is an anaerobic drying sealant which only dries where there is no presence of air, so any excess will remain unset and will be washed away by the engine oil when the engine is run. Simply put, I think it is the perfect product for this job.

Here's a photo of a 9m Race engine going together, showing the Loctite 574 sealant on the face (one face only, other side of the case is dry) as well as the o-ring on the #8 (nose) bearing on the crank. This o-ring must be fitted into a clean case with a light coat of grease to allow the rubber to "flow" around the bearing and sit perfectly into the machined hole. For the record, sealant should never be used around any o-ring because it will stop the seal from doing its job.

Whilst we are here, the reason why your only nose bearing is leaking is probably because the oil drain slot in the bearing is full of sealant. The slot vents oil from behind the o-ring back into the case, so if the slot is compromised the oil pushes past the o-ring and out of the front of the case, which is probably why the OPC has band-aided the leak with a liberal use of external sealant.

Another detail photo of the slot in the #8 bearing.

Great stuff Colin, always enjoy learning something new from your posts, thanks for taking the time

Thanks Colin. Do you use any sealant around the nose bearing when fitting it or is it fitted dry?

No sealant should be used on the bearing at all. Use clear grease on the red rubber o-ring and don't worry about the outside of the bearing being slightly greasy upon assembly. The #8 bearing has a larger scallop/notch in the other side where the oil is supplied to the nose of the crank from the case. The oil will naturally work its way around the bearing, simply relying on the close clearance to provide a high pressure drop back into the case, hence any sealant in this gap will compromise the performance of the seal and the bearing.

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