I originally posted this info on the different original 66 GT350 S2MS Cobra intake manifold variations on forum 1.0 in 2008, about time I got around to reposting. This is just my observations for 66 street cars, would like to hear what others have observed.
The variations are based on three criteria shown in the photos below:
1. Firing Order location:
A. Rear pad
B. Front #5 runner
2. COBRA casting style:
A. Square in the area of the "A".
B. Angled in the area of the "A".
3. Manufacturer stamp on the bottom front casting boss:
A. OECO (stands for Offenhauser Equipment Company)
B. OFFENHAUSER
A number of people with original intakes responded with their Shelby VIN and intake styles back then, please feel free to do that here, hopefully we can update this info. Some VERY general observations on how these fit with 66 GT350 production based on those responses:
1. Rear pad firing order location was found well into production, the front runner location seems to be a fairly late thing.
2. Square casting style found primarily on early cars. I assume the switch to the angled style was to reduce potential distributor interference (?), total speculation on my part.
3. OECO manufacturer stamp also found well into production. The OFFENHAUSER stamp seems to also be a very late detail and roughly coincide with the firing order on the front
runner. For both styles there are 2-3 letters also stamped in the same location, I assume some of these are initials of whoever cast or inspected the intakes.
Ten years later there are probably more details and variations known, please post if you are aware of them...
Thanks,
Dave