C2 Carter Carb Question

[Jack H.]

Just pulled the AFB off of my '65 327/300 mt. car to send it off for rebuild/restoration. The ID # on this carb is 3721 SA with K4 stamped below the 3721. The NCRS Spec. Guide calls for a 3721 SB. Is there a significant difference between the SA and SB? Is this carb incorrect as far as Flight judging goes? My car, VIN18420, was built on 25 May, 1965.
Thanks. . .

[Joe L.]

Re: C2 Carter Carb Question

Jack-----

As far as I can tell, they are functionally identical and can be used interchangeably. As far as whether only the "SA" is considered correct for judging, I don't know.

[Jack H.]

Re: C2 Carter Carb Question

How 'bout the "K4" stamp? Is this manufacturing date-related maybe?

[John H.]

Re: C2 Carter Carb Question

Jack -

The "K4" signifies October, 1964.

[Jack H.]

Re: C2 Carter Carb Question

OK, then is this carb correct for a May '65 L75 mt?

[Page C.]

Re: C2 Carter Carb Question

In my opinion, that would be a stretch. 8 months is not your typical time frame on the 3721 AFB's. I would think a March or April of 65 would be a better fit. Suggest that you check with whoever is going to restorer it and see if he has a closer dated AFB.
Regards
Page Campbell

[Jack H.]

Re: C2 Carter Carb Question

Good idea! Thanks to you and Joe and John for your responses.
Jack

[Jack H.]

Re: C2 Carter Carb Question

One more question. For a L75 car built the third week of May, 1965, should the 3721 SB carb have an April (G) or May (H) date code? I intend to exchange my 3721 SA (K) for a date-correct carb, if possible.

[Timothy B.]

Re: C2 Carter Carb Question

Jack,

I would go with the April date for the 3721. I don't know when the change from SA to SB took place so you better check before exchanging your carburetor. I believe the difference between SA/SB is jets, metering rods and also air bleeds located in the primary venturies.

[Mike McKown]

Re: C2 Carter Carb Question

I'm thinking there was a TSB that covered the SA/SB carbs?????????????????

[Dwight P.]

Re: C2 Carter Carb Question

Jack:
According to the 65 Judging Manual(Page 94)the changeover from SA to SB occured approximately November 1964. Your car shoul have a 3721SB dated sometime prior to 25 May.

DP

[Jack H.]

Re: C2 Carter Carb Question

Thanks one and all. This information was extremely helpful.
jackcasa

[Clem Z.]

Re: C2 Carter Carb Question

the SB specs are rod #16-388,.073 X .060,pri jet 120-224,.099, secondary jet 120-176,.067. the SA was jets .104,.0689, rod .060 X .069

[Timothy B.]

Re: C2 Carter Carb Question

Clem,

That's a big jump to the lean side from SA to SB. There is good archive info from years ago about these specs, I believe the 1963 Corvette 3461S carburetor has the same jets and metering rods as 3721SA.

[Clem Z.]

Re: C2 Carter Carb Question

i got these numbers from a original carb i rebuilt. i was supprised when i saw what was in it but checking farther i found out it was correct.