There are a plethora of differences but your general statement about the gear stack is accurate. I looks similar.
The major difference is the 904 main shaft, gear ratios and the additional oiling hole in the intermediate plate to lubricate the main shaft bearing. This design feature was transferred to the mid-engine transmissions used in the 914/6 but not the 914 /4 cylinder cars.
As you look at the case you will notice that it has extra fins for cooling and structural rigidity. Although it looks similar to the 901 aluminum case, it is in fact sand cast magnesium.
There are also additional bosses for mounting the trans into the chassis. Looking at the shift selection fork you'll notice a large bolt in the center. That is an additional detent designed to aid in rapid shift selection.
Looking through the hole you might be able to notice that the LSD is tiny. It is haft the diameter of the 901/915 LSD ad half the weight.
The output shafts protrude from the differential unlike the production piece. These shafts have an external spline design adapted from the 904.
I believe the flanges are identical to the 904.
The last major difference is the provision for the shift shaft. As you can see, the shift shaft is accessed under the bell housing. this design is different from either the tail shifter or side shifter of the production models.

The master technician behind the hammer is the legendary Dean Polopolus (the designer and builder of the Polo 4 cylinder 911 engine).
This adjustment technique proves that "old habits die hard." :)

I use only 3 and 4 arm German made yokes. After 30+ years in the business I have never had or seen a problem. If you're buying a cheaper Chinese made yoke perhaps extra reinforcements makes sense. I really don't know.

What was he adjusting with the hammer?

Endplay.... ;)

Hi Henry,

Do you have a pic of the combustion chambers? Those pistons have a huge dome. Whats the compression?

Thanks
John

Cam Chains
 

Henery
It appears thgat you are using aluminum chain wheels. The 1973, and later RSR also uses those aluminum wheels. The RSR parts book shows an unusual Porsche part number for the RSR chains. Different from a normal split chain, or non split chain. Do you know why the RSR has a different chain number? Do you use anything special chain wise for the aluminum wheels in your engines,

Mike Curnow

I forget what its called but its a standard coating for protecting mag. I think its called gold wash or something. I know you can order it from West Marine. There has been allot of discussion about using it on mag wheels before painting/powder coating. You can do a search. I know we discussed it at length on the NSR forum.

Second answer
 

James
Apparently you like to answer other peoples questions, INTERNET expert I guess. This is the second question I asked that you have answered, incorrectly. If you insist on doing this, read the question.
What is unique about the 1973 , 74, 75 cam chain? Part # 901 105 529 02, that part number is not the solid or split chain part number. I thought it may have something to do with the aluminum chain wheels since they are the only real unique pieces in the RSR valve train. Anyone have any facts, and not opinions?

Really? I answered the question from LJ851 and not you; and only because Henry didn't have better information when asked. ...and how was my answer incorrect? Incomplete maybe, but I don't think incorrect. Sorry to have to hash this out on Henry's thread.

sorry
 

J911brick
Sorry, I thought you were answering my question to Henry.

Mike

Attitude.............

I don't have a picture of the combustion chamber. It looks like an oversight.
The heads are basically the same as a 69 chamber with 12mm plug holes.

The compression was measured @ 10.8:1.

We use the racing version of the Iwis link-less chain.
993-105-529-00/255

Dow 7 is a chemical conversion coating which results in no appreciable dimensional change to the component. The surface of components coated with Dow 7 is changed to a brassy or dark brown finish depending on the alloy.

Seal
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The crank was made from a std/std 2.2 911 "S" crank. It can be replicated for around $1.2K if you supply the crank.

Yep, that what I was thinking of. Also known as "Magnesium Dichromate".


Magnesium protection

I really hope that some day I've got a good excuse to have Henry build an engine for me...

Matt - you will NOT be disappointed!

Hope you don't mind, Henry - it was a great experience (and mine was just a lowly T).

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Beautiful engine. Couple questions:
1. What oil pump did you use, and is it modified or different from a street pump?

2. Do you actually measure the Play-Doh after it squished, or just see if there's enough clearance?
I've been reading about the solder method, which holds up enough to measure.

Thanks for the pics, looks great.

The oil pump is a flow modified 3.0 911SC pump.
The substance is actually modeling clay. It is rigid enough to measure.
You turn the engine over, squish the clay and simply push the depth gauge through the clay to measure the thickness.
I've been doing it this way for 30 years. I have never seen a better way to check multiple clearance dimensions.

Very nice build. Brings back old memories...

Great engine. Henry, years ago you posted a thread about your own 81mm 906 cylinders with later sealing surface (link http://forums.pelicanparts.com/911-engine-rebuilding-forum/288133-81mm-906-cylinders.html). Why was it not chosen for this engine?

The 906 cylinders are already aluminum and dual/full finned so we took the original 906 cylinders and had the Chromal stripped off. Then we had Millennium replace the Chromal with Nikasil. This made the old cylinders better than new.
We chose not to run my cylinders because the 906 heads have too much value and modifying then seems somewhat sacrilegious.
We actually welded a set of 906 heads recently to bring them back to original.

Awesome. More please... I need another fix!

Hi Henry,

May I ask what is the black coating used on these fasteners - and why?
Looks very good to me, something distinct from the yellow zinc plating we're used to see here!

That does it. If I need a rebuild, Henry gets it. Fantastic stuff here!

I am curious about the fasteners also! Could they be black oxide? But if I had to guess I would say they are zinc plated with an olive drab chromate. Could it be so? If so, that would be too cool for school.. I was thinking of doing that on my motor instead of yellow zinc. Better corrosion resistance, and looks bad ass.. but I am worried it might be too thick for the fasteners to thread correctly. This is based on zero experience on my part.

his prices are very reasonable for what you receive back...= a very well built engine w/ long life ahead of it...

In a resent thread, I was accused of "archaic methodology" so in this case that claim fits (at least on the outside).
The hardware is black oxide because in 1964 most of the 906 hardware was either black or clear cad.
With some of these projects, appearance counts almost as much as performance.
Strangely enough, this engine had a premature failure do to what appears to be a lack of proper hardness on the lash caps we purchased from Porsche Motorsport.
Sometimes even sourcing parts from the "best" supplier can throw you for a loop.

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Guess I should have stuck with my first hunch based on period correctness... Maybe zinc with black chromate would give one both proper appearance and up to date performance, but maybe the thickness issue I was worried about becomes a problem then. Thank you for sharing this engine with us!

Thanx for the info, Henry - while black oxide then probably wouldn't be the best idea for ordinary cars driven in ordinary corrosive environments... I can totally understand that yellow zinc plating wouldn't be authentic for this very special application :)

I believe the term was "antiquated" but that is another discussion/topic.

Shame to see the engine failure.

Working with aged/used parts often means you're either lucky or dead even when greatest lengths are taken to inspect, refurbish and source suitable replacements. Comes with the territory. Hopefully the owner understands this is an inherent risk of mechanized toys.

Andrew, you never cease to amaze me with your absolute grip on the obvious; thank you for that.

Just to be clear for those who seek accuracy, the failure was simply excess valve clearance.
Valve noise caused by lash cap failures. After the replacement of lash caps, the engine runs perfectly.

Would you have preferred me to use more color and less tact similar to that which those afford me?

Unfortunately not everything from Porsche Motorsports... is what it seems.. We sourced some Pankl ti rods for a cup engine a few years ago from them.... They were delivered in a large padded envelope 6 Ti rods, just tossed in a padded envelope... not a thing to prevent contact between the rods....

We thought for about a second that we might try to use the rods... until we took a close look... and saw the nicks and blemished that were present from the way the rods were shipped....

Returned to PMNA

Hi Tim
Thanks for the input.
Your issue sounds more like competence in the shipping department as opposed to quality control.
We have rarely seen an issue with quality from PMNA but with the advent of sourcing small quantity items for vintage race cars (old street cars as well) from previously untested or new management suppliers, we really have to be on our toes. I feel certain that this lash cap issue will be address but after 30+ years I'm constantly surprised at where the next challenge will come from.