# 1966 Carter Carburetor dashpot



## gtoguy389 (Jun 3, 2012)

I am looking for information about whether or not the dashpot was used on all Carter 4 barrels, or if they were transmission specific, automatics or manuals. Thanks for any info. Scott


----------



## rickm (Feb 8, 2012)

my '65 shop manual shows them on automatic trans. cars. I don't have one on my 4-speed.


----------



## gtoguy389 (Jun 3, 2012)

Thanks rickm. My 4-speed carb doesn't have one either, and I know it is original to the car. I just bought a Carter AFB and a '66 intake yesterday to use as spare parts, that one has a dashpot on it. After I got it home and started doing research on it, the carb tag is missing, but investigating the casting numbers on the body, the airhorn, the metering rods and the venturis, it appears to be a '65 GTO automatic carb, #3896. I was led to believe that I was getting a '66 carb. I might have to clean the carb up and try to recoup some money from this deal. I will keep looking for that elusive 4033 4-speed carb.


----------



## 1966 GTO KID (Oct 10, 2011)

*Would like to get up to speed on this Carter topic*

Bottom line, what is the difference between a Carter #4033 versus #3896?
I have a Fremont built 4 speed '66 GTO with original Carter 3896S that I have owned since December 1967 - I am the second owner. I was told these Carter 3896 went on 421 CID Pontiac High Performance engines back in the day.
I always like to learn a little more about Pontiacs in this era and time frame.


----------



## gtoguy389 (Jun 3, 2012)

I do know that the 4033S was used on the base 389 335 hp with manual transmission, either 3 or 4 speed GTO. The information that I have been able to gather is that the 3896 was used on the 1965 GTO 389 335 hp 2-speed automatic, and possibly, but not sure about, the 421's. The research I was able to find is that there were very small differences in the manual and automatic transmission carbs. Here are the differences that I found.

Low speed jet size: 3896 .035, 4033 .040
Idle bypass size: .052 .057
Idle economizer size: .051 .0571
Idle air bleed size: .059 .052
Idle port size: .200x.030 .205x.030
Secondary discharge port size: .0465 .0635 (possible typo, both could be .0635)
Metering rod high vacuum diameter: .0655 .068
Metering rod low vacuum diameter: .054 .058
Primary jet diameter: .091 .0935


----------



## gtoguy389 (Jun 3, 2012)

I would also like to add that the casting numbers for the air horn and body were different, as well as the part numbers for the venturi clusters. And the metering rods were also stamped with different part numbers making it easier to tell the size of the rods.


----------



## Rukee (Feb 8, 2007)

What is a rebuildable Carter worth? I have 2 that I believe from `65s. 1 has a tag, I'd have to dig it out to read it.


----------



## 1966 GTO KID (Oct 10, 2011)

Was it possible back in 1966 that Carter was not able to produce enough 4033's and had to substitute the 3896 for GM production schedules?
When my 3896s was professionally rebuilt the research showed it being used on 421 CID high performance engines, again perhaps a supply issue for Carter and having cars roll of the production line.
My 1966 4 speed GTO was made in July 1966 and came with the A.I.R. system.
As a footnote, driving this set up in 1967 this car flew and literally dominated the road.


----------



## Rukee (Feb 8, 2007)

Wow, Carters were used on everything!!
Carter 4-Barrel Reference Numbers | Hemmings Motor News


----------



## gtoguy389 (Jun 3, 2012)

My car was built in June of '66 and has the 4033 on it. This 3896 that I picked up over the weekend was also on a July built '66. Is it possible that a batch of those carbs got lost in the system and didn't reach the assembly line until that time? I got that carb and the intake for $200, and I thought I had over paid for it. But the carb is a good rebuildable core, everything moves freely. Just needs a good cleaning. It came with the throttle bracket, original return spring, and the dashpot, which is how this whole thread got started.


----------



## 1966 GTO KID (Oct 10, 2011)

Do both the 4033 and 3896 have the same CFM rating?


----------



## gtoguy389 (Jun 3, 2012)

I do believe so. The primary and secondary throttle bores are the same size, 1-7/16 on the primaries, and 1-11/16 on the secondaries. Also the primary venturi were both 1-3/16, and the secondary venturi were both 1-9/16. All the internal differences that I stated earlier were to compensate for the automatic transmission. Looking at my sheet, of the 1964-1966 that it lists, 1965, both auto and manual was the only year to use smaller jets on the primary side. (1964 and 1966 used the same jets). Also all automatic transmissions 1964-1966 used a Hot Idle Compensator.


----------



## 1966 GTO KID (Oct 10, 2011)

Thanks for all your feedback & information - it is very much appreciated.
Factory Original is literally what GM factory geographic location built your GTO at and what was available at the time.
I have heard of Oldsmobile engines in Cadillacs at the time of production with full exposure and negative publicity in the news at the time. Also, GM building diesel engines using a "conventional or non-diesel engine set-up".
Bottom line, I have always enjoyed my GTO & no complaints in the Pontiac method and approach to performance.


----------



## gtoguy389 (Jun 3, 2012)

I did finally find that the dashpot was originally used on automatic transmissions, just to answer my original question.


----------

