[tom s]

Steve,I think most of the early 60s 2 bbls are the larger ones.They did have a economy engines that would use the smaller carb.Tom

[mgarblik]

That is a Rochester 2-jet carb for sure. The carburetor shop is a fine choice for a kit. Another option is to contact Cliff Ruggles in OH. for a kit I have used several of his kits and they are very top notch. I strongly suggest NOT buying a kit from a parts store like NAPA, Oreily's, Advanced Parts and so forth. Rock Auto included. These kits contain old, crap rubber parts that will fail in very short order with modern fuels. The carb will give you trouble in a month or two, almost guaranteed. Beginning with the accelerator pump. You don't want to be doing this again in two months. Good luck.

[Tomaso]

Thanks guys. I will get a kit and rebuild this one. If it's the good 2 bbl carb. Would it be good for a street driver for now? Any huge difference vs going the 4bbl

[Sirrotica]

The Rochester 2GC is the small 2 bbl used for the center carb on tri power setups through 1965, until 1966 when they went to the larger 2G center carb.

The 2GC was used by itself on late 50s, early 60s 420E engine option through the 1962 model year. Starting in 1958 the larger 2G Rochester was the most commonly used carb on Pontiac factory 2 bbl V8s, and the 2GC was available from 1955 through 1957, and was only used on the 420E "economy" option through 1962.

The 420E option was rare in most consumer cars, most likely was more commonly ordered on fleet cars such as taxis.

[Tomaso]

Originally Posted by Sirrotica

The Rochester 2GC is the small 2 bbl used for the center carb on tri power setups through 1965, until 1966 when they went to the larger 2G center carb.

The 2GC was used by itself on late 50s, early 60s 420E engine option through the 1962 model year. Starting in 1958 the larger 2G Rochester was the most commonly used carb on Pontiac factory 2 bbl V8s, and the 2GC was available from 1955 through 1957, and was only used on the 420E "economy" option through 1962.

The 420E option was rare in most consumer cars, most likely was more commonly ordered on fleet cars such as taxis.

So I wonder if it was factory ordered? I wonder why they went with the 2bbl on such a big car...
I already ordered rebuild kit and with rebuild it for now.
Until I do an engine rebuild for now .

As of now, I cant even drive the car around because of it

[steve25]

Probably so!
In 66 the top of the line B body cars I would think got the big Carb, and the special order 256 hp 389 likely got the smaller Carb pearched on it.

[Sirrotica]

In my earlier post, the 2GC is the smaller carb, and was only offered until 1962 with the 420E engine option. From 58-62 the common 2BBL carb was the 2G, only way to get the small 2GC was to order the 420E option. Beginning in 1963 the only 2 BBL carb offered by itself was the larger 2G (tri power still used the center 2GC carb until 1965). After 1962 there was no option to get the small 2GC carb by itself on a 2BBL engine.

The difference in HP ratings on 2 BBL engines was high compression versus low compression, they both used the same 2G large carb, but you could order a premium fuel 2BBL engine making more HP. Both options still used the large 2G carbs. In 1966 there was only one 2 BBL carb available, the 2G large carb on 2 BBL, and 3X2 BBL engines had also been switched to the larger 2G center carb for more CFMs.

[hurryinhoosier62]

Originally Posted by Tomaso

Attached are some pics. What do you think?

Definitely a Pontiac 389 with a 2CG carb. My dad's '68 Catalina had the same setup but was a high compression engine(290hp).

[Jerry H.]

I thought the Bonney's in those years came with a 4 bbl standard. I guess you could have special ordered the economy engine. But I make be mistaken.

[77 TRASHCAN]

Originally Posted by Stuart

I'd suggest going to The Carburetor Shop for a rebuild kit, to make sure you get a high quality one. Jon is a member here on the board, and knows Pontiacs and carburetors inside and out. http://www.thecarburetorshop.com/

X2!
Your carb has a tag on one of the top screws, gently remove it, straighten it out and re-install on your rebuilt carb. It’s pretty rare to see those tags these days. The number on the tag is your carb number.
Jon only takes orders via phone, and only on Monday’s and Tuesday’s
, the rest of the week he prepares and ships orders. I have no idea what his price will be. Whatever his price is, just pay it and go on! His kit will be better quality than anything you buy at a parts store, and his stuff is ethanol resistant

His phone is 1-573-392-7378 Jon Hardgrove is his name.

Be gentle with that small tube that comes off the passenger side and goes down into the intake , it’s fragile and can twist easily.


Jerry, I would have thought 4Bbl’s on Bonneville’s also? My good buddy that would know, passed away in 2018 (aged 71), Parkinson’s took him. I used to have a. 64 Bonneville, 4 door hardtop, was a cool car. Jerry, I pray you are doing well!!!

[Sirrotica]

I've rebuilt and worked on a whole bunch of Rochester 2 BBl carbs, even built a couple for 2 BBL only racing classes on the local oval track guys. That carb in the picture is definitely the larger 2G not a small 2GC. The vent tubes are very different in the air horns, plus Pontiac never cast a late style manifold (65 and later) that had the correct flange pattern for a 2GC. The choke chamber is also a dead give away that it's a 2G.

The 420E in 1962 was the final year Pontiac cast a single carb manifold for a 2GC flange pattern. You cannot bolt a 2GC on a 2G manifold, or vice versa because the stud holes aren't in the same place and because they overlap they are only adaptable with an adapter plate. Been there, and have tried to do it, it can't be done without a plate. The stud pattern overlaps and the adapter has to be tall because the stud placement are stacked on top of each other, but offset about half the size of the 5/16 inch studs 1/8" to 3/16" overlap. The throttle bores are centered differently on the 2 carbs too. They have to have a specific intake manifold for each carb bolt pattern.

OP, you definitely have a 2G not the smaller 2GC carb.

[Stuart]

Originally Posted by Jerry H.

I thought the Bonney's in those years came with a 4 bbl standard. I guess you could have special ordered the economy engine. But I make be mistaken.

For Bonnevilles with automatic transmissions, a 325hp four barrel premium fuel engine was standard, according to the factory brochure: http://www.oldcarbrochures.com/stati...estige-50.html A 256hp two barrel engine was available as a no cost option.

[lust4speed]

I've got a '65 Star Chief with the 389 two barrel carb that was standard on that model, and that carb is a 2G. So while the 1965 Tri-Power had the small center carb, the standard two barrel was large even that year.

The two barrel carb and the cam that came with it complemented each other and adding a four barrel carb and manifold is only going to improve the looks of the engine compartment.

[carbking]

Originally Posted by tom s

For a driver I would go with the factory 4 bbl intake and factory AFB.To save weight a Performer and the factory 4bbl AFB.Carbs are reasonable and many guys rebuild them.Tom

Yep! Plus, everything fits!

Jon.

[carbking]

There seems to be some confusion on this thread concerning the terminology. Rochester started with the type A carbs, the next series was the type B, and the third series was the type G. The type G was produced in both 2 and 4 barrel versions.

The letter following the type (or the lack of one) designated the choke type. Thus:

2G - 2 barrel no choke
2GC - 2 barrel integral choke
2GV - 2 barrel divorced choke (the "V" came from the use of the external (V)acuum choke pull-off.

One cannot tell whether the carb is the small base or large base from the type alone.

Jon.

[1968GTO421]

Originally Posted by Stuart

I'd suggest going to The Carburetor Shop for a rebuild kit, to make sure you get a high quality one. Jon is a member here on the board, and knows Pontiacs and carburetors inside and out. http://www.thecarburetorshop.com/

I agree with Stuart, you can't beat the Carb Shop for quality and I've even got tech advice from them. Skip Rock Auto.

[Sirrotica]

Originally Posted by carbking

There seems to be some confusion on this thread concerning the terminology. Rochester started with the type A carbs, the next series was the type B, and the third series was the type G. The type G was produced in both 2 and 4 barrel versions.

The letter following the type (or the lack of one) designated the choke type. Thus:

2G - 2 barrel no choke
2GC - 2 barrel integral choke
2GV - 2 barrel divorced choke (the "V" came from the use of the external (V)acuum choke pull-off.

One cannot tell whether the carb is the small base or large base from the type alone.

Jon.

Jon, even if you're 67 YO you learn something new everyday, I learned something new today. The hot rod group in nearly everything I've read since the 60s has referred to the larger bore (1 1/2 inch) bore carbs as 2G and the small bore (1 1/4 inch) carbs as 2GC carbs. I mistakenly also referred to his carb as a 2G which upon further clarification should be referred to as a 2 GC large bore carb. I do know that his is a large bore from the pictures just from working on dozens of them over the years.

Sorry for the error on my end and thanks for the education on bore size and model clarification. I'll be wiser from here on out.

2GC large bore carb is what you're working with, OP.

Since I've transplanted a few Carter AFBs (Aluminum four barrel) onto 2BBL engines, putting the same setup on this 389 would be a good upgrade IMO, if you can find a good serviceable unit.

[carbking]

Brad - glad you liked the post.

I should have given examples.

2G - outboard carb on Pontiac tripowers. 1957-58 small base; 1959-66 large base.
2GC - center carb on 1957-65 tripowers
2GV - center carb on 1966 tripowers.

Since the thread was about the 2G, 2GC, 2GV series; I just started the history with the type A, and ended with the type G. Rochester also produced the type H (Corvair), type R (turbo Olds), and the type M (later, which superseded the B (single barrel) and 4G (the 4M is a spread-bore a.k.a. Q-Jet). Of course, all of these models also have the letter modifier for the choke type.

And to the OP - as others have mentioned, the Pontiac with the two-barrel runs very well for a cruiser. If you want to go with a 4-barrel for any reason; either the stock 1966 intake with the stock Carter AFB 4 barrel, or a stock 1968~1970 intake with a stock 1968~1970 Q-Jet. The Q-Jet will get slightly better fuel economy for city driving. The AFB will deliver the same mileage on the highway as the Q-Jet, and has the added benefit of increasing the universe of potential buyers if you (or your estate) decide to sell the car.

As far as performance is concerned: this is the street forum, not the race forum. For a basically stock Pontiac engine in a Bonneville, the skill of the tuner is more important to the performance than the brand of carburetor or intake selected. But just guessing, I would say that if you were to have any of several folks on these forums build for you a Q-Jet, an AFB (genuine, not the current clones), and a Holley as mentioned by some on this thread; and run back-to-back-to-back testing on WOT zero-70 (speed limit in Missouri) runs, all would be within a tenth of a second. Some really sharp folks on here.

Jon

[389]

The stock Carter AFB with the stock square bore intake is hard to beat...

[HWYSTR455]

Originally Posted by 389

The stock Carter AFB with the stock square bore intake is hard to beat...

Getting a 'true' 'AFB' carb that is rebuildable is an issue tho.

If you're going 4bbl, the support, ease of tuning, and available parts of a Holley is still a better choice than going QJ, AFB, and an OE intake.


.