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That sender sticking out of the case towards the distributor is the oil pressure sender.  It turns the idiot light on and off in the tach gauge.

Many of us run a "T" out of the case at that point, then attach both temp and pressure senders there.  Yours works just as well at the dipstick.  

Six of one, Half dozen of the other....

For a more detailed explanation of the gauge info, thou shalt consult "The Holy Book of Annunciators".

@ALB posted:

His words Danny- "And no internal vanes to route the air evenly over the four cylinders". It doesn't matter who made the shroud or what fan it's using; if there's no directional work inside the thing won't come close to even temps from cylinder to cylinder.  I stand by what I said.  Just look at all the work you did to make it work satisfactorily.

Actually, it DOES matter who made it. There are different shrouds, some are not shaped in a "cooling air flow" fashion. Bergmanns absolutely SUCK in this regard. Look at photos on the web, you'll see what I'm talking about. Al, it seems that you completely missed my point about a sealed plenum. Think about it for a minute.

It wasn't that much work. There is a factory part available for the P shroud, but only if it's modified a little. And it will only fit a real Porsche alternator and ring.

I stand by what I've said and done. The axial fan works on pressure, the regular VW fan works on flow.

The sled tins made a LARGE difference. TEN degrees cooler in all conditions. Why? I think because the air is forced to follow along the cylinder bottoms, thereby removing MORE heat than if the bottom of the cylinders is open.

The shroud Martin has looks really close to mine. The "wings" that he has that go under the stainless fan clamp are absent on mine, but the rest of the shape is the same.

Martin, I also used silicone to seal some areas that the foam weatherstrip wouldn't fit. AGain, pay special attention to the top and sides of the case, and your fan ring to shroud joint.

Here's the Porsche part I modified. There must be a reason the factory put it in there when they went to the 2.7 liter. The vanes go on the left, to turn the air opposite to it's natural direction on the 3-4 side:ALternator vane


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Inspecting the dipstick, I spotted a very tiny '150C' cast into the plastic casing at the top and, testing it with a gas torch it read 0 ohms until it reached temp (presumably 150C/ 300F, although I've no real way of knowing) then generated a reading, so obviously a warning light switch rather than a gauge sensor.

Looking at the 911 fan air guide/ Yoda Ears fabrication (thanks @DannyP), in theory it could be a reasonable task to create out of sheet metal - create a cone with tabs to allow mounting to alternator, then bolt or rivet vanes to the cone. The problem is knowing how sturdy to build it - I'm betting there's quite a force of air being blown down at high revs. As Danny says - with the 911 fan it's all about air pressure. Having seen this, I googled and found a useful blog of a guy refurbishing his 911 broken air guide - this image taken from his site to show just how it mounts on the alternator (picture credit:


Here's the back of my alternator/fan to show where it would have to be attached.


So, that's one to ponder for the moment. I have an old friend who does some fabrication so I may have to give him a call and see if he can help.

Another task to ponder is the oil breather system. Currently there is a large stainless steel breather box mounted in engine bay (nearest the bumper). Oil breather pipe layout

As well as the two vents at the top of the box, it has hoses going to:

  1. Left side rocker cover
  2. Right side rocker cover
  3. Crankcase - there's a fitting in the fan base that replaces the old oil filler casting.
  4. Oil filler tube - it taps into a bodged fitting screwed into the side of the plastic filler funnel which sits atop the oil filler pipe.

My plan is simply to clean everything up and replace the hoses with new hoses. So, is this a good idea or not? I'm also considering hoses with slightly smaller ID - they're a loose fit on the 11mm (7/16") diameter fittings, causing more oil leaks! There's hardly one part of the underside of the engine that is not covered in oil from one leak or another..

Tied in with the above task is the oil filler tube - it's far too short, causes oil leaks and is not easy or convenient to use for it's designed purpose - to pour oil into the engine.

oil filler tube

20210128_09565720210128_09573720210128_095812As you can see it's already been welded/modified to fit. It could do with being 3" taller. Is this a modified Type 4 filler? Any suggestions on how I can improve this situation please?

As always seems to be the way in car maintenance, my thread is a prime example of "While I'm in there" scope creep. :-)


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I agree with Ed.  If anything, either try the right hose size for your fittings, whatever they are, or spring for fittings the next size larger with hoses to match.  

Smaller hoses might lead to restriction in the breathers and subsequent spewing of oil out of any space it finds.  I went through this a while back and ended up with a CB Performance upright breather, similar to the original Porsche breather but made up as a  spiffy-looking, ribbed aluminum box as part of the oil filler with 5/8" hoses from the breather to the carb air cleaners.

The oil filler tube looks like something for a Bus.  The new AS41 cases have that flange in the sump, too.  Since it has an extender on it already, you have the option of cutting that one off and welding a longer one onto the existing fill pipe or just adding an extension inside of the top section.

And then, of course, you'll find another few things that you think need attention along the way.  You should meet @Michael Pickett over in Hawaii.  He went through this on his car for what seemed like a long time (but was about a year).  He finally got it to where he wanted it and we haven't heard from him in a while so he must be out burning up the asphalt on Maui.

Now you know about the"Madness".  It consumes you........

Good luck fabricating that alternator cone. You can find them used instead of making one. It's not a simple shape.

I'd simply extend that filler tube and get new hoses. Make sure they are oil-safe. If you were going to increase the size of any of the hoses/fittings, the driver's side valve cover would be one and the pipe in the alternator base would be the other. The crank throws a LOT of oil toward the 3-4 cylinder side, not so much to 1-2.

On my 911 fan setup I plugged that pipe in the alternator base. I made a 3/4" I.D. pipe to my breather that goes in the distributor hole(I know not an option for you).

I agree with everything everybody's saying regarding pretty much just cleaning up the breather system you've got and running it. I also agree with @DannyP regarding buying a 911 cone and adapting it, rather than fabricating it-- but I didn't miss this:

oh, and one other thing - there was no woodruff key locating the fan to the alternator spindle. So I fabricated one up last night. Luckily it hadn't caused a problem in the past, but at least this should prevent a problem in the future.

It's hard to know on the internet who's god fabrication skills and who doesn't, but I get the feeling that Tigermoth knows his way around a shop.

Good on ya', mate.

Ok, @Stan Galat, I think I massively oversold myself with 'I fabricated..', more like 'I made' - there's not a lot to making a woodruff key, just a solid piece of metal in a particular shape. All I needed was a larger piece of metal, a hacksaw and a file! I only wish I knew my way around a MIG/TIG welder. I will have to call my brother (who's only 12 miles away) or friend to see if they can add on a few inches to the oil filler pipe.

Guys, thanks for the tip about breather hose size. I must admit I didn't think of a hose enlarging and sagging over time. The fittings are all 5/8" OD so I'll get a hose with 5/8" ID.

And as for the cone, thanks for reminding me to consider the easiest option, Danny. Obvious case of not seeing the wood for the trees.. A quick search on UK eBay and there's one in good secondhand condition for £100 ($137) including delivery. Sorted! And a LOT less hassle. Fingers crossed it will fit once I get it next week.


"...there's not a lot to making a woodruff key, just a solid piece of metal in a particular shape..."

Still, some of us would have just jammed in a screw driver and broken off the handle.

Some others would have worked out the forces applied, calculated a 50 per cent safety factor, and ordered in a slab of a suitable alloy from the Frumpster-Magee catalog.

Some members would have researched which woodruff key was specified in Germany by the original German engineers for the exact German model upon which your car is based, and would have then tracked down an old-stock part from that year of production, even though shipping times from the Alsace region are currently running from six to eight weeks.

There are those who would have used a similar VW part but, figuring that was about 40 per cent stronger than required and thus 40 per cent too heavy, would have then spent several weeks making suitable modifications to reduce the weight by 39.7 per cent.

And then, there are those of us (a very small number) who would have built a steam-powered woodruff key fabrication machine, just for the sheer joy of having accomplished such a task.

I commend you on having focused on the task at hand and having found a simple, workable solution close to home so that you could ask what is probably the most important question in these projects:

What's next?


@Sacto Mitch posted:


"...there's not a lot to making a woodruff key, just a solid piece of metal in a particular shape..."

Still, some of us would have just jammed in a screw driver and broken off the handle.

...There are those who would have used a similar VW part but, figuring that was about 40 per cent stronger than required and thus 40 per cent too heavy, would have then spent several weeks making suitable modifications to reduce the weight by 39.7 per cent.


That's cutting it a little close.  A really smart man would only rework it to 25 or maybe 30% lighter; then there's a little room for miscalculation/error

@ALB wrote “A really smart man would only rework it to 25 or maybe 30% lighter; then there's a little room for miscalculation/error”

True.   Maybe it would be better to Laser-drill a bunch of “micro-holes” in it instead, thereby attempting to maintain structural integrity?    😆


When I had a bunch of mechanical designers working on my projects I was forever impressed with how much those guys knew about basic metallurgy, almost as a cultural thing.  Things I never even thought of, but they just knew.

I was first impressed by the electronics guys achieving what seemed like “magic” out of electronic circuitry, especially on the scale of a large-scale computer server, but those Mechanical guys just quietly went about their work and knew far more about working with different metals (and against a product cost target) than I’ll ever know.  Those guys were Rock Stars!

My first degree was from Univ. of Kansas, and I worked in a motorcycle shop and raced short track and scrambles.  One of the really good riders from the shop became obsessed with weight on the short track and started drilling holes in just about everything, and then started removing spokes from the wheels...yes, for weight!  Here's a surprise, Frank (now long gone) lost a front wheel in turn three and did a high side flip.  He lived but was busted up.  The guys who did nothing for weight focused on h.p. and technique.  Some of your guys seem to be engineer types.  Where does the goofy line cross the sensibility/physics line on the graph?

@Sacto Mitch posted:


In Baltimore, it's not the lawyers I'm worried about.

They say Argentina is nice this time of year.


It's beyond "nice." This is summertime and the weather is great! Northern Argentina is anywhere from the 60'sF to 90F.  The most southern tip will be chilly (40's to 50's) but you probably wouldn't be going there unless you were on your way to Antarctica. Learn a little Spanish and go on down there for the best steaks you can find...anywhere. Argentina is definitely not a destination for vegetarians!

Many thanks Danny, those pics are really useful. Hopefully the cone should arrive Thursday, along with numerous other parts and breather hoses.

I re-read my first posts on this thread this morning and boy, have I learnt a lot in just over 3 months! Thanks to all of you on here who have been patient and helpful with advice and knowledge. I hope you're still enjoying me documenting my work. As most of you know, there's simply no substitute for taking everything apart and putting it back together again.

So, a quick update from the weekend. Most of it was spent getting rid of the paint on the fan shroud. Almost 2 days work has resulted in the matt white gelcoat you see here. For info, the shroud is a very close fit and cannot be removed without the alternator mount in place. With deep shielding it does direct the air well down past all cylinders (cylinders 2 and 4 shown here)


and the gaps around the inlet manifolds and plugs are very tight.


You can also see the engine bay opening for this Chesil version - kind of a D shape.


The vertical covers at the back of the engine bay need to be replaced - the left one you can see has a gap where it wraps around the shroud and no. 4 cylinder. I'm currently making a card template to fit the gaps. I'll be allowing a lot of overlap and making the 'tinware' out of ally with rubber leaf seals to seal the edges. I can get the aluminium in either 0.8 or 1.5mm. Probably going to go with the 0.8 because it's easier to work (unless any of you tell me differently) and clad the underside with glued/pop riveted heat shield.

Although I quite like the idea of a white fan shroud, I would still have to paint it because it's not 'optimal' quality as it stands, and if I'm going to paint it, I think gloss black will be neater, not show the marks and look better against all the cleaned maniofolds/carbs etc. So black it is. I'll fill a few scratches and gouges in the fibreglass before painting and hopefully I can get this done this week before the cone deflector arrives (although I now have 3 rooms to paint indoors as well, since the Long Haired General has gone back to nursing to jab patients with Covid vaccines).

The incentive to get the car finished, at least to a point where it's on four wheels again, is huge - my wrist has now (almost) recovered from surgery enough to ride my motorbikes. The bikes are trapped at the rear of the garage behind the Speedster - so nothing is moving until the Speedster moves!


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So, a mixed day today.

Good news - the rotary fuel pump arrived (SO much quieter than the Facet solenoid pump), so I completed the refurb of the entire front end fuel system with the large Mahle fuel filter and the rotary pump, new braided fuel hose back to the engine bay, new fuel sender pipe with internal filter, and a cleaned (rust free) fuel tank inner.

This kills multiple birds with one stone - the glass fuel filter, the noisy pump, the deteriorated fuel lines and dirty fuel tank. The yellow stopcock still allows for easy fuel filter replacement.


Now the bad news - I received the secondhand Porsche fan nose/vane in the post, only to find it doesn't fit any of the mounting points of the alternator. <sigh> Looking at things more closely, it appears my alternator is much deeper than Danny's, meaning it pokes out the back of the casting by roughly an inch.


Oh well, I can use it as a rough guide to get a local welding/fabrication firm to build one when they also fix the exhaust and extend the oil filler tube. Luckily, living close to Portsmouth harbour and plenty of leisure and commercial shipping services, there are plenty of local welding/fabrication firms I can call on to help.


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$240 at AutoHaus for the 75 amp model, but the note on this reman indicates tricky fitment.

"Due to possible dealer TSB updates made to original alternator, we highly recommend verifying the Bosch, Porsche or Valeo part number on your existing unit when ordering. If the alternator mounting and air guide have already been modified to accept the updated AL400 design, please let us know. If updates have not been made, the modifications should be done by trained personnel with correct update parts. 1 per car."

I've got a GREAT fab shop I use for everything (business and car stuff).

The shop has a quintessentially "Peoria" story. The owner (in his mid-80s now) served an apprenticeship as a sheetmetal worker, and started a fabrication shop 50+ years ago, catering to Caterpillar and John Deere. At one point he had a couple hundred employees and about 2 acres under roof (10+ big lasers, and attendant everything else). He sold the company at the peak, but retained ownership of the real estate.

Gary (the guy) has a different late model V-Series Cadillac for every weekday. He's got a couple of drag cars and a nice (but unassuming) house.

The new owners ran the company into the ground, and Gary bought everything he wanted back on auction. He moved the machine and fabrication tools into one of the smaller buildings (maybe 300x100) and hired his "number 1". He's got a full powdercoat line in addition to the fabrication shop.

He futzes around in there, just for something to do. People from all over the Midwest bring him cars to do metal fab work, and he does it (if the muse strikes). They do a lot of one-off and small batch laser work for specialty shops. There's no sign on the door. You need to know somebody to know they're in operation.

GMH Fabrication's work is almost perfect and laughably cheap. I think they are billing at south of $50/hr, but I don't know-- I just pay whatever Gary's wife bills me, and am happy to have it.

That vane would run me at least twice the cost of a new alternator at GMH, and that's assuming it would work.

Thanks guys. I think I've finally spotted my real problem - a lack of threaded holes in the fan case to hold any such vane.. The straight on picture in my post of the 28th Jan above almost shows it but this oblique view shows it better:20210128_095948

So no wonder the vane wouldn't fit - I was hoping it would mount against the 4 bolt hole of the alternator (2 currently filled with bolts holding a protective plastic case at the top of the alternator). If I remove the current alternator, it looks like there are no holes on which to mount the vane. And I don't want to start drilling holes in the 4 deflectors on the fan case.

Another difference between the two fan surrounds is the outer edge of my fan surround is smooth, not ribbed like Danny's (ooh, Matron).

I've got so much else to do on the car to get it running I'm tempted to let this sit for now - the car ran 6,000 miles prior to my ownership without any specific air direction to No3 cylinder. Then again, that's why it ran a bit hot compared to the others, as evidenced by slight scorch marks on the fibreglass shroud around the no3 exhaust port. It's not ideal but..

At least I can try and remove the alternator to see how it is mounted and whether something like the Valeo alternator could be fitted, and whether that would allow me to fit the vane by some kind of adaptor plate (which would be far simpler to fabricate).

I'll talk to a couple of local firms and see what they suggest but in the meantime I could  go ahead and reinstall everyting to at least get the car running again and revisit the cooling vane situation at any time - it's v easy to remove the fan from the shroud. If you'd ever heard the car run (pops and bangs on steady throttle as well as on overrun, fuel starvation above 3k revs) you'd understand why I've got more pressing matters than a no3 cooling issue.


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Martin, that's weird indeed. My fan ring has a 901-XXX-XXX part number, so early 911. The ring has to be chucked in a LARGE lathe and cut down to fit the aluminum base. I sent my whole setup to Jake Raby, he cut the ring down so he could dyno my engine that he built for me, back in 2001-2002.

There are no studs or bolts on the ring, the alternator has 6 long studs that go through the ring and vane. Then 6 nuts hold the whole thing on.

Danny, ok, that's good to know about the studs being on the alternator, not the ring. And also about cutting the ring diameter - would that explain the lack of part number on the ring? I presume so, but if mine was reworked to reduce the diameter, they did it major league style - there are no ridges, grooves, part numbers or anything on this baby! It's like a CIA wetworks gun - no traceable markings. ;-)

So, I went out to the garage and took these pics. What they prove to me are:

a) quite apart from the lack of part number, the only distinguishing mark on the ring is the extra depth of the ring around 1/4 of the circumference on the right of this pic.



b) I can't get the existing alternator out of the casing! There are 4 long bolts that attach from the 'front' of the casing to the alternator (below) but if I undo these it's still wedged in firmly. There are three threaded holes in the centre of the assembly below which look to have bolts screwed in from inside, but I've no idea how to take this further..20210205_165013



Looking at the Valeo alternator, there is a Valeo option here in the UK (£260 + delivery) as well as Mahle (£166) and some unknown brand for £71! Worth investigating. But first I'm going to measure the ID of the space the alternator fits in. I've already bought something without doing enough homework, so don't want to repeat the event!


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Yeah, it looks like they machined a lot of meat off the fan ring, whereas Jake only took off the minimum.

I'd bet a local auto electric guy could help you out. He'll know how to get that alternator out, and may be able to suggest a replacement too work with your vane thing. I'm curious how it attaches also. The six bolts are supposed to hold it in.


It looks similar to some of the DELCO alternators used in some GM cars and trucks.

If it is, the bearing is pressed onto the armature shaft and into the cover depression at the same time (or into the cover first, then the cover and bearing as a unit onto the shaft, if you prefer).  Easy to do with an arbor press and a suitably sized deep socket.

To get it apart, a special bearing puller is used into the three central holes of the cover (if they are threaded) then the center bolt of the puller is pressed against the end of the shaft.  Tighten it and the cover is pulled off.  If the three holes are not threaded, you can use a suitable gear puller into a couple of the larger holes near the shaft, center bolt of the puller against the end of the shaft and tighten.

Regardless, the puller won’t damage the shaft.

OTOH, any competent alternator repair/rebuild place could pull that off in a couple of minutes without damaging it.  

Thanks Gordon. Don't worry, it was only the smallest of taps - I wasn't going to inflict 'blunt force trauma'. I'll leave that until I cabn find a local alternator shop.

Meanwhile, the gloss black engine paint (spray) worked well on the fan shroud:

20210206_110925 20210206_163238

I'm now fitting stuff roughly together whilst I await the aluminium sheet to replace the old tinware around the engine bay.

As an aside, it's amazing how many extra tools I've acquired over this winter specifically for this project. I thought I had a well-stocked garage already - sockets, spanners, power tools, all the usual stuff, plus air compressor, etc. I had even kept a VW gearbox hex tool from 30 years ago, just in case I'd use it again.. In the last few months, I've bought an ultrasonic cleaner, vernier calipers, a rotary buffer/grinder, thread count gauge, label printer (for wiring) and now I've bought a metric tap and die set.


These have already been useful in helping clean up the threads on wheel studs/nuts - it seems they're a very tight fit between the drilled disc conversions and the fake Fuchs alloys.

What next?? :-)

And since this morning was likely to be the best weather for some time (snow forecast tomorrow), the Long Haired General and I took the dog for a walk along the seafront at Lee on Solent, which looks out to the Isle of Wight on our south coast.



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