Crank to Cam dimension on 616 engine.

[Jacques Lefriant]

No Larry
i have good gears and cams laying around and if i build engines i like to do 4-Cams and 2 Cams (six cylinder (911)). I am conteplating using that 3 sided Polygon coupling on the camshaft drive gears for the 4-Cam it provides the same adjustability as the 6 spline original versions.
j

[Albert Tiedemann]

Pictures of the connective piece found in industrial engines posted earlier by Jan could be envisioned as the center section of an Oldham coupling. I made this comment in an earlier post. However, strictly speaking, the input and the output ends of the coupling should be fixed.

I do not think that this part is/was envisioned to be used like the center section of an Oldham coupling. The régime of significant coincidence disparity between the axial axes of the driven oil pump gear bore and the camshaft should be small-- since the dimension in both the crankcase and the timing cover would have been called out to be the same on the Factory drawing [good engineering practice] although it has been purported to wander all over the place. This dimension would correspond to the center distance of the timing gear set which would be a basic dimension on the Factory drawing that would be for “the gear set” for the application. It would only be speculation as to how it actually was called out or its value [since no one has yet to pony up the Factory drawing].

Moreover, the input “disc” of the coupler [camshaft] and the output “disc” of the coupler [oil pump driven gear shaft] are not fixed as both units have specified new clearances as well as wear limits viz., axial play. Acceptable rebuild tolerances for the former might be in the .12 mm range and the latter can be adjusted to the lowest limit new which would be on the order of .05 mm depending on the engine under reconstruction. Since the center section must traverse an orbital path about the midpoint between the camshaft and the driven oil pump gear axial axes---no mater how small—there must be clearance at the camshaft slot and at the slot in the industrial engine connective piece for the oil pump gear tang to permit this motion. If indeed this is the case, axial excursion could result until the tang of the oil pump shaft and the imaginary extension of the tongue of the connective piece touch. Apparently, not a problem for the industrial engine.

[Gary Koehler]

Ibrahim,

I think your best bet would be to measure a new factory replacement case. There may be a member near you who has one that you could measure. And if your existing case has been line bored, there is added uncertainty that it could introduce some error as it’s more of a bench process as opposed to a machining setup. The replacement cases also bring better machining capabilities some 20 years later.
I have a complete factory replacement case here in CA, but no longer have access to my CMM since retiring.

[Jacques Lefriant]

Hi Gary
i think what Ibrham wants to do is make replacement third pieces to fit existing motors. As Ab points out we believe that the factory used the the 2 holes as tooling points. Ideally you would take the third piece to be replaced and find the locations of the features and then transfer to the new part.
j

[Ibrahim Kuzu]

Guys,as usual you are great and please keep the ideas coming ...
After casting the New Timing cover we need to call the perfect Cam center on the other hand
the oil pump shaft will eat away material from the casting...

Gary, I would be happy to buy the NOS replacement case from you or borrow for measurements to compare other cases
with deposit for return...

Jan,
Thank you for posting pictures of the coupling.

Larry,
Thank you.
Great point...Make sense...
Lets try to eliminate more work on this new timing cover installation...

Idea is ;
Just swap the old timing cover with new one with out machining anything on the existing engine...meaning ,not taking a part.
and also there will be some engines building from zero....But aim is just take your old timing cover and by changing few 8mm studs
install the new timing cover and new twin Dist.drive gears ...Done....

Here is an idea:
Since factory did the Cam coupling to try to eliminate oil pump shaft corner damage...Why not offer this Coupling
with our new timing cover.

In order to use our regular oil pump shaft, all need to be done is arise the oil pump casting and machining 5mm away from cam....

What is the opinion about this?

This way because the Cam coupling has tight fit to oil pump shaft ,we can even use the corner damaged oil pump shafts with out any problem
this way we do not need to make 5mm short oil pump shafts and do more parts and expense...
IK

[Jacques Lefriant]

Hi Ibrahim
Obviously you have never had to change out timing covers or deal with badly line bored cases or cases that have been shaved. Sometimes you have to delete the dowel pins and take your best guess. I don't follow your reasoning on the oil pump drive. you should offer your third pieces with new pump gears and shafts. I will have some available soon. Check with me. Also if you want your castings machined i can help you.
j

[Gary Koehler]

Hi Jacques,

Re your comment,
"i think what Ibraham wants to do is make replacement third pieces to fit existing motors".

No argument there, but the original post was 'what is the c-c distance between the cam and crank'. If using 2 holes as a datum (and by this I presume you mean the aforementioned 2 dowel pin holes) you still would want to know the c-c distance for the third piece and/or the case as best you can, and the the subsequent x-y coordinates to the 2 dowel pin holes. Hence my suggestion of measuring it all on a virgin case with a CMM.
--------
Ibrahim,

Are you coming out to the Left Coast? It's certainly possible to find a CMM here in the Bay Area where we could measure this if you have the time.

Gary

[Jacques Lefriant]

Gary
For a while i linebored hundreds of VW and Porsche cases. When doing the 3 piece cases we did not necessarily bore the #4 bearing bore but used it to align the boring bar. The best way to fit the third piece would be to bore the #4 using 1-3 as the center line since the dowels would be holding it in the same position. You could use a case as a jig and do the final bore on #4 And the oil pump shaft. Other than those dowel holes i am not aware of any tooling points.
j

[Ibrahim Kuzu]

Jacques,
Thank you for the offer...So far all good in here,have good set up.Oil pump gear would be great ,we will get to it when
we are ready...I will call you...

Gary,
We will talk on the phone...will be in touch in future...so far we are still working on preparation for casting model....

IK

[Craig Richter]

Ibrahim,
I loved Larry's + shaft idea, and J's polygon offering is truly elegant, but Jan's pictures of the industrial drive piece are brilliant! And real 356 Porsche. This is the first time I've ever seen one of these pieces. You don't even have to mess with the cam, just a simple machine shop operation could save all those "corner worn" shafts, slip in the drive piece, and maybe double engine life expectancy! Is this too good to be true?

[Brad Ripley]

All of the industrial engine drive pieces are sold now; we have no more. BTW, that drive kit was not in any of the industrial parts catalogs; I understand they were used in the last run of engines to the Swiss Army.

[Jacques Lefriant]

Hi Ibrhim
final machining of third piece on an engine case.

[Ibrahim Kuzu]

Craig,
As you point it out, I think it is great to save all the corner damage oil pump shafts and re use them if the gears are OK
on the new timing cover.
We will add 5mm more material on the oil pump casting ( The industrial Coupling is 5mm thick, therefore factory made oil pump shaft 5mm short
on these engines only )

Jacques,
Thank you for the picture and all your input on this fun project...

Brad,
If you like, make more couplings...I could buy from you for my new timing cover..It is all up to you..
IK

[Brad Ripley]

Not me, that will be up to Jacques.

[Steve Proctor]

Probably don't have the real estate to facilitate, but I've always thought it would be neat if the cam bores were of greater diameter than the cam lobe height (like a Chevy) and the cam followers could be retracted so you could change camshafts without a complete teardown and splitting the case.

STP