Intake manifolds info

[1QuickS]

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 manifold (mfg 1966) has 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 manifolds have the same 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 the 1968 manifold, it is part of my show display so it was painted black for uniformity with the other manifolds in my display.

Manifolds through the 1968 year model may have been coated with a protective finish while the 1969 and later manifolds were painted with a VERY tough, gloss black coating (polyurethane?)

Also, I expect there are variations of the castings with common date codes; in other words, early in 1967 the manifold would be as shown in the photo while later in 1967 the design would be advanced in preparation for the 1968 year model.

[preS]

Nice sum up Paul.

The Weber's on the 911 were introduced in February of '66, engine no, 907001

Richard

[1QuickS]

Thank you Richard! I amended my original posting with your info.

[Bert]

Hi Paul,

Your summary is very helpful Do you have any suggestions on how to strip and refinish the manifolds to protect the magnesium surface from corrosion?

Thanks,

[66S]

Im pretty sure the black manifolds have a Teflon coating to help move gas droplets faster. Like the 69 912 black manifolds.

[JimVillers]

Were the 1965-67 manifolds painted or coated with a protective coating?

[1QuickS]

Hi Bert,

Some recommend using POR15 and then coating with Gibbs, I have done this but am concerned about durability; finished color is dark grey.

Dow 7 conversion coating can result in various shades of brassy yellow to brown depending upon immersion time, again protect with a Gibbs coating. This process could be performed at home but the conversion coating uses hydroflouric acid which is evil bad stuff!!!! Source for the Dow 7 is: http://www.chemical-supermarket.com/...ound-p652.html.

I just found a supplier for a conversion that has promise and it is a replacement for the Dow 20 which tends to be black/grey. Any conversion coating is subject to being defeated rather easily depending upon environment/maintenance. Link for the supplier of Dow 20 replacement: http://www.saporitofinishing.com/processes/nh35 but it is unknown if they perform odd jobs.

Ultrasonic cleaning or pressure washing followed by blasting with plastic media is best; sand cast items may be soda or glass bead blasted but bead size should be small and pressure kept down when using glass. Both soda blasting and bead blasting will texture the surface; the die cast items have a smooth surface.

[1QuickS]

Hi Jim,

The Feb66 through 67 manifolds were as-cast without paint finish and perhaps finished with a conversion coating, beyond that I don't know. Six, 40PI Solexes were used from 64 through Mar66 and had a gold iridescent finish which is (to me) unknown how to replicate exactly.

[304065]

Paul, the early (no buttress) manifolds had plating and conversion coating the same as the early Solex manifolds. This was applied after casting and prior to final machining.



In your photo above, the bottom ones (the earliest with no date codes) have had this coating removed, that is why they have turned grey.

This is very hard to replicate accurately!

[Bert]

Thanks Paul.

Hi Bert,

Some recommend using POR15 and then coating with Gibbs, I have done this but am concerned about durability; finished color is dark grey.

Dow 7 conversion coating can result in various shades of brassy yellow to brown depending upon immersion time, again protect with a Gibbs coating. This process could be performed at home but the conversion coating uses hydroflouric acid which is evil bad stuff!!!! Source for the Dow 7 is: http://www.chemical-supermarket.com/...ound-p652.html.

I just found a supplier for a conversion that has promise and it is a replacement for the Dow 20 which tends to be black/grey. Any conversion coating is subject to being defeated rather easily depending upon environment/maintenance. Link for the supplier of Dow 20 replacement: http://www.saporitofinishing.com/processes/nh35 but it is unknown if they perform odd jobs.

Ultrasonic cleaning or pressure washing followed by blasting with plastic media is best; sand cast items may be soda or glass bead blasted but bead size should be small and pressure kept down when using glass. Both soda blasting and bead blasting will texture the surface; the die cast items have a smooth surface.