I believe those are from a Sportomatic installation and for a 1968 year model. The manifolds for a 911S will have exit port diameters of nearly 36mm while the other ones are 32mm. All die cast manifolds share the same casting part numbers and all have date codes on them. I attach some info which is helpful:
Intake manifolds info
I have reviewed a selection of OEM intake manifolds to help answer some questions regarding individual variations between the years from early 1966 through 1970. I have a sample of manifolds for each of these years which I reviewed so I feel confident the gamut of variations is pretty well covered. Each of the manifolds has a date of production except for the manifold I believe to be the earliest which is sand cast and doesn't have a date.
Info presented in no particular order:
• I have one set of sand cast manifolds without mfg date
• All other manifolds are die cast
• both types of 1966 manifolds (sand cast and die cast) have an oblong, internal cross-section in the outer runners
• 1967 through 1970 manifolds all have conical bores
• my 911S manifolds (mfg 1966 and 1967) have a 35mm bore in the middle and has oblong outer runners
• 1966 manifolds (sand cast and die cast) have 34mm bores
• 1967 through 1969 manifolds have 32mm bores; 1970 bore measured 31.5mm
• starting in 1967, reinforcing ribs extend from the bottom flange up the exterior of the runners; 1968 and later manifolds have larger and longer reinforcing ribs
• starting in 1968 the lug for the 8mm bell crank has an added reinforcing web
• sand cast manifold part number is: 901.108.321.01
• die cast, 1966, 911S manifold has part number: 901.108.321.0R
• die cast, 1966, Normal 911 manifold has part number: 901.108.321.1R
• 1967 and later have ports for Sportomatic and/or other vacuum accessories
• The two measured manifolds (sand cast and die cast versions) are magnesium. I measured volumes and weights (volume by water displacement method a la Archimedes), I then corrected for steel studs that were installed. My calculated densities matched the published density for Mg to the second significant number (density for aluminum is 56% greater than Mg and well outside my tolerance band); I conclude that all I have are magnesium.
• My inventory included manifolds with dates from 1966 through 1970 without interstitials.
Remember that the manifolds for Solex carbs were magnesium so I expect Porsche would keep the material for Weber carbs. I assume the sand cast manifold was for the first few Weber 911s which began to appear in Feb 1966 with engine #907001 as the Solex carbs were phased out.
Ignore black finish applied to top three manifolds. Earlier manifolds may have been coated with a protective finish while later ones were painted with a VERY tough, gloss black coating (polyurethane?)
Also, I expect there are versions with date codes that would fit into the above collection such as those manifolds made in 1967 but do not have the changes that the manifold I have that show for 1967, in other words I bet there are 1967 manifolds that physically match the die cast 1966 manifold.
