66 GT350 S2MS Cobra Intake Manifold Variations

[s2ms]

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

[6s1640]

Hi Dave,

Very nice again.  Can you ID what combination sets of the three variables you have found?  There are eight possible combinations shown below.  Which combinations have been observed by the community.  Respondents can ID the No. combination set 1 through 8 and the SAI VIN.  Is there a pattern?

I just checked a loose intake.  It is a combination set No. 1.  I do not know the history on it and can't say if it was OTC or an assembly line part.  Based on you other observations, this would appear to be an early intake with the square COBRA casting style.

Cory

[kingchief]

Hi!  Can anyone please direct me as to where the manufacturer stamp is located?

Thanks,

Steve

[kingchief]

By the way, which one is this one???

Steve

[gt350hr]

   Steve ,
      On the underside of the manifold there are two round "post looking" areas. The stamp is on one of those . As an FYI , I have seen genuine assembly line intakes that missed getting stamped with the OECO stamp. They are rare but are out there. The other inspector stamps are there , only the OECO is missing. I have also seen both "posts" stamped as opposed to all on one and even seen a drilled hole into the post.
   Others will have other opinions/experiences/observations.
      Randy

[gt350hr]

By the way, which one is this one???

Steve

       Generally it's a '65-66 carryover intake.  It is possible some of the post 252 vin cars had them but my experience is that '66 chassis cars had large letter ( S2MS) intakes. without the "notched" A.
     Randy

[s2ms]

Hi Dave,

Very nice again.  Can you ID what combination sets of the three variables you have found?  There are eight possible combinations shown below.  Which combinations have been observed by the community.  Respondents can ID the No. combination set 1 through 8 and the SAI VIN.  Is there a pattern?

I just checked a loose intake.  It is a combination set No. 1.  I do not know the history on it and can't say if it was OTC or an assembly line part.  Based on you other observations, this would appear to be an early intake with the square COBRA casting style.

Cory

Hi Cory,

Yeah, I was thinking about combinations when I wrote that, thanks for the chart, makes it easy! I need to find my spreadsheet from the old post which has the reported combo's. Personally I have seen combo's 1, 3, and 8. I'd be surprised if there were any 2, 4, 5, or 6 combo's but who knows. The one I'm curious about is combo 7.

Thanks,
Dave

[CSX 4133]

I'm either category #7 or #8.  If I can find the manufacturers casting identifier it will narrow this down.

[shelbydoug]

I'm either category #7 or #8.  If I can find the manufacturers casting identifier it will narrow this down.

They are on the underside so if it's installed you aren't going to see it.

[jk66gt350]

Mine is either a 7 or an 8.  The post with the manufacturers stamp has markings that are illegible.

[CSX 4133]

I'm either category #7 or #8.  If I can find the manufacturers casting identifier it will narrow this down.

They are on the underside so if it's installed you aren't going to see it.

Mmm... I'll remove the intake tomorrow then and have a look. Thank you !

[kingchief]

Mine is #1 or #2 and is like "a '65-66 carryover intake" [like the photo above that I asked about].

Cheers,

Steve

[6s1640]

Hi Steve,

Is your intake a small or large letter COBRA?  The S1MS would suggest a small letter COBRA, which falls out of the survey.  Dan Case has been watching the small letter intakes and has quite the list of variations.  If you have a large letter COBRA, your intake will now add more variables to this survey, the part number on the rear runner, S1MS or S2MS.

I will also note, there is only one vacuum port on your intake, where the S2MS's that Dave is tracking has the two.  Again, if your intake is a large letter, this will introduce another variable, one or two vacuum ports.

Cory

[GT350Lad]

I am a combo #1
Cheers

[kingchief]

Hi Cory,

Mine is an S1MS with small letters [Cobra].  Yes, you are correct.  Mine only has one [1] vacuum port as well.  I should have kept quite...never mind. 

Thanks for correcting me.  I apologize for the confusion on my part.

Cheers,

Steve