The Official 356Talk Forum

I have a '55 3-pc case 546/2 motor and am trying to make sure I have the correct set of parts for it. Does anyone know when the intake manifolds changed from the type with the bolt together balance tube connections to the type with the cast in connection piece?

Alan,

The intake manifold with cast-in nipple for the balance tube was an improved design for the type 616/1 and 616/2 engines. Your 1500 Normal engine originally would have had the earlier manifold design pictured below- - - -- -

thanks Don.

Weren't the 616/1 intakes a bit taller than the 546 and 546/2 versions pictured above? That necessitated the use of the same throttle linkage rod used by the 616/2 and 528/2 engines.

James Davies wrote:Weren't the 616/1 intakes a bit taller than the 546 and 546/2 versions pictured above? That necessitated the use of the same throttle linkage rod used by the 616/2 and 528/2 engines.

I think you are correct.

Amazing what you guys remember right off the top of your heads. 8)

James, The 546 manifold is quite a bit shorter. Left to right in attached photo: 616/2 Super, 616/1 Normal, 546 Normal, 528 Super.

Great photo Alan! Thanks.

That photo is a good example of Porsche figuring out better air flow into the heads.

Yes Vic, and also cost savings. The number of bespoke parts required for building normal and super engines side-by-side on the production line went down significantly. With the 1600 engines, normals and supers now used the same throttle linkage rod, same spark plug engine tin and same balance tube.

James Davies wrote:Yes Vic, and also cost savings. The number of bespoke parts required for building normal and super engines side-by-side on the production line went down significantly. With the 1600 engines, normals and supers now used the same throttle linkage rod, same spark plug engine tin and same balance tube.

And same heads. No longer small ports for Normals and larger ones for Supers.

True! Though I think the first 616/2 heads were different from the 616/1 heads. They had a a split down the middle, partially separating the head for each cylinder, though I think this was only for a short time in 1956.

And perhaps the 616/2 heads also had a fin in each intake port shrouding the valve guide? I know the 528 and 528/2 heads had this fin. Did the 616/1 heads have this fin?

3-piece case heads only had the fin starting with the C, SC heads.
Not many heads here anymore of the earliest type, so I can't vouch that the 616/1 heads did or didn't have the fin.
I wasn't aware that the 528 heads had the fin; always thought they were somebody's porting efforts.

Since we seem to be getting into sort of esoteric trivia on very early parts I noticed that there are at least three versions of the 546 manifolds. The earliest (I suspect) is a version with fairly crude castings and totally separate ports at the head end, photos attached (ignore porting which has been done to this particular manifold). The next iteration is the manifold shown in Don Zingg's photos which has pockets in the casting at the head end, perhaps to save material or perhaps to allow better stability for the manifold/head joint but still with totally separate ports at the head end, and the last, and most common, iteration adds cuts to allow a balancing passage between the ports at the head end, photos attached.

Alan, that's a really lousy example of porting. Just making holes match gaskets is not porting, it's turkeyizing.