Why are late cam towers so hard to find?

[Lukesportsman]

With short blocks, 3.6 cranks, and P&C's all being marketed and several set of heads....where are the cam towers going? Is there something going wrong with 3.6 cam towers or why the scarcity? Opinions, reality or better IF you have a set you'd part with let me hear what you got. Cheers

[targa72e]

the 3.6 cam towers are unique because of the oil feed. The 964 and 993 are different. The 964 used mechanical rockers like all earlier engines. The 993 has a different cam town and used hydraulic rockers. When people make a track 993 or build a higher performance (RPM) 993 engine they want to replace the hydraulic rockers with mechanical and this requires a swap to 964 cam housing. As a result of this 964 cam housings are hard to find and expensive. I don't know of anyone manufacturing new cam housings. I have compared 964 cam towers to earlier units and it does look like it would be possible to machine early housings to work with 964/993 oil system but that adds cost. You would also need to use early style cam housing covers.

john

[Peter M]

Don't forget the later 3.2's used 964 cam towers, complete with 964 part number, so you may want to broaden your search. The only difference being the 3.2's used meaty 8mm studs to hold the rocker covers on while the 964's used 6mm ones.

[mikedsilva]

Originally Posted by Peter M

Don't forget the later 3.2's used 964 cam towers, complete with 964 part number, so you may want to broaden your search. The only difference being the 3.2's used meaty 8mm studs to hold the rocker covers on while the 964's used 6mm ones.

I just checked some parts listings and they suggest a 930 part number for early 3.2 and late 3.2.
930 105 021 00

[targa72e]

While its possible the later 3.2 engines may have used the same casting they are machined different. When used on the 3.6 engines there are no external oil lines from the case to the cam tower. On the 3.6 motors the oil is feed thru the timing housing. The 3.6 cam housings are not threaded for oil lines instead are machined to accept the oil "bridge" and are sealed with a o-ring.




John

[Flat6pac]

Production of 4 bearing carriers began on the 3.0 and 901 carriers were used until the castings were depleted and replaced with the 930 carriers.
Bruce

[Peter M]

John,
You are correct that the oil feed is different and you would need bore the threaded hole to accept the spigot and oring setup used in the 964/993. I'm a little embarrassed at my oversight as I've actually replaced these orings on a 3.6 but obviously have a hazy memory...…

Mike,
Yes, the PET references a 930 part number but Porsche produced the last year or two of 3.2's with a 964 casting. Here's a photo of a Dec 87 build:


Ignore the 964 rocker covers and the CoP's as they're not OEM....

[Lukesportsman]

All great info. Guess I'll continue to hope for someone breaking a 3.6 for the short block and hope to scarf up a top end. I'm in line to get one of the new 3.6 blocks and am hoping to NOT break any of my complete engines. May end up simplest to buy a high mileage 3.6 and sell off everything I don't need or want. I'm plannig new p&c and I've got a gt3 crank and oil pump so short block is pretty freed up already.

[DMadigan]

Not to change the subject, Peter M - what COPs are you using? Kettering or CDI? From the three wires I presume power, signal ground?
I am twin plugging my '73 2.8L and want to machine new covers with mounting holes for the COPs. All my searches for COPs do not give dimensions which seems rather stupid.
I already have drawn a cover for the stock sticks but that would require six dual output coils and COPs would be neater. Thanks.

[Peter M]

Originally Posted by DMadigan

Not to change the subject, Peter M - what COPs are you using? Kettering or CDI? From the three wires I presume power, signal ground?
I am twin plugging my '73 2.8L and want to machine new covers with mounting holes for the COPs. All my searches for COPs do not give dimensions which seems rather stupid.
I already have drawn a cover for the stock sticks but that would require six dual output coils and COPs would be neater. Thanks.

DM,
If you have a look down the bottom of this page under the thread title "Twin Plug" all the detail on these CoP's and the other common alternative is discussed:

https://porscheforum.com.au/topic/15418-my-carrera-32/

I went direct fire CoP because I wanted the engine bay to look standard....until you notice there is no distributor. I was also confident that the CoP's had sufficient spark power/duration for my needs.

[DMadigan]

Thanks. I am trying Denso 90919-02239 used on Celica, Corolla, Matrix because they "look" shorter. If they turn out to be too short I probably can use them on my Europa. Ballenger claims they are reliable. They give a pin-out but I question their pin 3 (also reverse order from this diagram). Here is an ignition system diagram -

Pin 1 : + power
Pin 2 : signal power (probably +5V)
Pin 3: trigger
Pin 4: ground

[dap930]

Pin 1 - 4 designations are looking into the coil connector. For aftermarket ECU's, pin 2 is not used. Pin 2 provides a tach signal to the factory ECU.

[Peter M]

Originally Posted by dap930

Pin 1 - 4 designations are looking into the coil connector. For aftermarket ECU's, pin 2 is not used. Pin 2 provides a tach signal to the factory ECU.

Dennis,
I thought Pin 2 was used as part of the diagnostic trouble code system on modern cars to allow a misfiring cylinder to be identified?

[Lukesportsman]

Got excited......lol no tower offers.

[DMadigan]

Pin 2 may be used for tach input but it seems unlikely. Why would you need a signal from each coil? At 1000 RPM the update is 60 msec for one coil and I doubt a mechanical tach could keep up at four times that rate.
The IGF labeling on the ECU might be a clue, something like Ignition Fail if IGT means Ignition Trigger?
I will check it out with the oscilloscope.