3.0 camshaft housings on 964 heads?

[Aircooled4evr]

hi all my fellow pelicans.

I'm in the process of rebuilding my 3.0 engine. Have already decided on 964 - 100mm pistons & cylinders, CP connecting rods, and raceware headstuds.
The one that promised to machine the 3.0 (SC) heads for double ignition, has made such a poor job of it, that I'm looking for a new set ....
This time I will NOT gamble with the extra sparkplug hole! And thought, if a' 964 head could be paired with the aforementioned SC 3.0 cam-box (house?)?
I can buy a good set, with new valves in Germany for 1,800 Euro (about 1,980 $) and would rather work a little with the external differences of the two! (if possible, I get other benefits from the 964 heads)

Have any of you tried this operation, please tell me!! what are your experiences?

Cheeres, Mads

[drgouk]

The problem is the 964 head stud pattern is different from the 3.0. The 964 cam housings will fit your 3.0 heads, but 964 barrels/heads won't fit.

[Henry Schmidt]

Originally Posted by Aircooled4evr

hi all my fellow pelicans.

I'm in the process of rebuilding my 3.0 engine. Have already decided on 964 - 100mm pistons & cylinders, CP connecting rods, and raceware headstuds.
The one that promised to machine the 3.0 (SC) heads for double ignition, has made such a poor job of it, that I'm looking for a new set ....
This time I will NOT gamble with the extra sparkplug hole! And thought, if a' 964 head could be paired with the aforementioned SC 3.0 cam-box (house?)?
I can buy a good set, with new valves in Germany for 1,800 Euro (about 1,980 $) and would rather work a little with the external differences of the two! (if possible, I get other benefits from the 964 heads)

Have any of you tried this operation, please tell me!! what are your experiences?

Cheeres, Mads

Head stud spacing is a relatively easy modification. We've been doing it for decades. Cam towers are interchangeable, in both directions. We recently modified 964 cam tower to be fitted to cases designed for cam feed lines.
The issue with 964 heads is that there are two different styles. Conventional head seal and what might be called "updated" sealing. The factory discovered that with a ceramic exhaust insert, the 964 head lacked structural rigidity. This compromised structure allows the head to bend between the head studs. This "bending" compromised the cylinder to head sealing. BY re-configuring the cylinder sealing surface and machining the heads flat they were able to support the heads where the clamping force is applied.
3.0/3.2 case mod is simple. Bore the spigot and relocate the studs (widen the stud spacing).
The cylinders need to have the spigot diameter reduced and a .280" spacer (base shim) must be fitted. (dimension is from memory)
Next the heads must match the cylinders. Early cylinders (when using wide stud spacing) will experience the head deformation. If using the late cylinders the head must be machined to match.
As for the original question: all 49mm cam towers are interchangeable. 3.0 to 964 no modification if used with a 3.0/3.2 case.

964 to 3.0/3.2 an oiling modification is required.

[Aircooled4evr]

As Henry writes.
Have tried Head stud spacing before, quite simple.
It was only if there were any issues with the fit between heads and cam towers, I was asking for. And oh yes .... precisely these "small", unforeseen problems when parrying different year engine parts.

And it certainly looks like Henry has sorted it out!

And as I read it
(English is not my first language, so I often need to get it bent in neon for me, to be sure I have understood it correctly) It fits together if using early 964 cylinders & late 964 heads.
On 3.0 block, and cam towers. (Is this correct understood?!)

Thanks for the reply and help Henry!

[Aircooled4evr]

ahem ... can see I did NOT understand it properly ...
I will read it thoroughly through a few more times ....

[Aircooled4evr]

Hmm ...
How about 993 heads ....

[Aircooled4evr]

Originally Posted by Aircooled4evr

Hmm ...
How about 993 heads ....

I was thinking of ceramic insert in 964 heads, versus non in 993 heads! ...

[Neil Harvey]

Originally Posted by Aircooled4evr

I was thinking of ceramic insert in 964 heads, versus non in 993 heads! ...

I responded to your PM with my email address.

I think you may have some issues with using the stock Piston. The dome volume may not be large enough and the compression height may be too tall.

I think the 964/993 heads have a volume of 90-91cc and the piston dome is around 35 cc. I may be wrong, but this is from memory.

Before you do anything, its best to check and calculate the final engine on paper before you buy parts that cannot be used.

I would also defer to those that have actually built a engine like this, with these parts as I may have it all wrong. Only measuring and doing some simple calc's will tell you.

[Henry Schmidt]

Originally Posted by Aircooled4evr

I was thinking of ceramic insert in 964 heads, versus non in 993 heads! ...

The ceramic insert has value but it is susceptible to cracking. We have a great method for repairing the ceramic.
That said the 993 head flow much better and the valves are lighter. That is the reason 993 heads cost so much more.

[Aircooled4evr]

First:
I HAD misunderstood it! The best (of the "cheap" solutions) will be late 964, or 993 cyl. with the large contact surface and compression ring. and then milled 964 heads to match.
next:
in fact I don't think 993 heads is right for my project after all ... Because I don't need better flow, for sub 300hp! this will just lower the flow rate, that dosent fit my desired engine characteristics.
last:
I do think about it before I buy stuff!
With original 964/993 pistons in ditto heads. (org. 11.3: 1) and a stroke length of 70.4 versus 76.4 I can measure that I have to "find" 0.5 mm in the combustion chamber, and with the 70.4 mm I will be able to achieve 11: 1 in the now 3.3l engine

Cheers, Mads

[Aircooled4evr]

Another "problem" ... the 993 pistons are too heavy. I'm probably going for CP Carrilo, or JE pistons ... (I'm not COMPLETELY done examining Wössner pistons either)