Rochester 2gc

B

bigcatchdaniel555

Well-known member
a buddy of mine has the rocheter 2gc 2bbl it came it came standard on most chevy smallblocks he wants to put it on his 200 but is unsure of its power compared to an autolite 2100 or holley 2300 i told him that most likely it wont come close to the holley but what about the autolite also he will have to fab an adapter or modify one for the base of the carb has anyone tried this what would be the easiest adapter. about the power issue the carb ist progressive like the 5200 so that would make sense to me that it has a definte power advantage over the 5200.
 
bigcatchdaniel555":1z9ne27x said:
a buddy of mine has the rocheter 2gc 2bbl it came it came standard on most chevy smallblocks he wants to put it on his 200 but is unsure of its power compared to an autolite 2100 or holley 2300 i told him that most likely it wont come close to the holley but what about the autolite also he will have to fab an adapter or modify one for the base of the carb has anyone tried this what would be the easiest adapter. about the power issue the carb ist progressive like the 5200 so that would make sense to me that it has a definte power advantage over the 5200.
Click to expand...

I'm not sure how well the Rochester 2GC carb will work compared to other 2 barrel carbs commonly adapted to the small Ford sixes, but I did find some useful links I thought I would share with you.

1964 Rochester 2G, 2GC, 2GV Carburetor Manual (published 1064)

Rochester 2-Jet Carburetor Manual (published 1973 - 1982)

Servicing the 1955 Eight-Cylinder Two-Barrel Carburetor - TOP-55-25 S&M

Rochester Two Jet (2G, 2GC, 2GV) Tech Info - The Carburetor Doctor
 
8) the rochester is a reliable carb that does indeed provide enough airflow for our little sixes. i have thought about putting one or two on my sixes myself.
 
thanks i have heard a lot of the good things abou the carb and since free is the best price anyone can get i will try to persuade him to put the carb on or give it to me. :wink: however i think the adapter that makes the most sense would be the one for the weber or 5200 anyone have any input.
 
I think Rbohm worded it properly "Air Flow". The power produced is based on the displacement and the health of the compression and ignition systems.

I look at it from the standpoint of how well the carb or injection can mix the fuel with the air. Put simply, the carb has the best chance of creating a good air/fuel mix if the velocity is kept at a high rate and the carb is capable of being adjusted at the point of fuel and air pathways.

The Weber and Holley 5200 design does both. The primary venturi is approximately the same size as the stock venturi which keeps the velocity up to normal levels. There is also a secondary venturi that allows for increased flow at the higher RPMs when needed. These carb designs also allows for fine tuning through the replacement of fuel and air jets for idle and main air/fuel circuits.

Check out the sticky “Holley/Weber 32/36 Jetting Tipsâ€￾ in this forum. There has been a lot of work finding the best combination of jets for this block. I plan on taking advantage of this experience as well.

Have fun, Ric.
 
Howdy Daniel and All:

About the only downside with the Rochester 2GC is that the accelerator pump is adjusted by bending the acctuation rod. It is difficult to be precise.

Another issue is the ability to tune. It uses a needle valve system, somewhat like the Quadrajet 4 barrels. It just makes it a little more difficult, but once tuned won't matter.

The narrower base bolt pattern may have some mounting advantages.

If you will post the throttle bore and inner venturi diameter I can estimate a CFM range.

The 2GC was used on so many different engine sizes at GM over the years, I doubt there is a standard, one-size-fits-all.

I hope you get to go with this. I'm curious about how it will work.

Adios, David
 
i persuaded my friend to let me try the carb first wink wink and see how it goes. the carb was brand new when he got and he put it on his fj 40 with a 232 i6 the motor ran awesome with it the car had great power and it felt like fuel injection the car never missed or shook. i actually found an adapter from summitt part # 2025 that is made for the 2gc air cleaner clearence wont be a prob because the carb already has a 1 in drop base it may be a while before i try it because i am still absorbing the a/c cost and getting the system charged and fine tuned.
 
the main reason i am going to atleast try this is because when i put ac in the car i lost some hp and i understand that a 2bbl will add some will it compensate for ac.
 
does anyone here have any expierience with the kickdown cable i heard that when a 2bbl carb is put on the car wont downshift making it bog how does one fix this i also just measured the 2gc and it looks to be a tad shorter than my old weber 32/36 so hopefully clearence wont be a problem
 
Some flow 367 cfm, the last of the Oddfire 231 V6's and some Chevy V8's were the bigger, about 430 cfm, if I remember Pat Ganhals V6 Performance artical correctly. There are still new old stock variants around for some oval track racing classes.

Excellent, leak free carb has horizontal float bowl split line, with Holley 2300 venturi centre spacings, and a compact base, and solid zinc oxide casting. Jetting can be varied to suit anything. Calibration tricks are not that hard.

All parent 2300 Holleys generally run a 0.3125" venturi to main throttle differential (350, 500), but the Rochester has more signal than that.

It can be fly cut for more cfm, and, since it can be found by the bushel in scrap yards, its really cheap.
 
i'm getting the rochester from my friend tomarrow and i will be using the summit adapter to hook it up th only question i have is how to tune it i have only done 1bbls and they only have 1 mixture screw how do you adjust them on a 2bbl. do you adjust one until the engine runs sort of smooth and then the other or do you tighten them both and adjust them both simultaniasly.
 
On 2 or 4 bbls I usually turn them both all the way in to get them both matching and then out one turn each for my starting point. After that I go 1/4 turns at a time on each one till I get where them where they want to be. If a 1/4 turn on one seems to smooth it out and you then turn the other one a 1/4 to match and it gets rough take them both 1/8 turn the other way to ballance them back out. I dont know if thats the official way to do it but it has worked for me over the years. Most of the time I have to go back and turn them all the way in because I loose count on which side I have turned and have to start over.
 
the adaptor just got here yesturday so i'll be putting the carb on hopefully tomarrow i would like to use the stock linkage because the car is an auto so putting a throttle cable on and getting the c4 adaptor kickdown is going to cost some $$. i have figured out a couple ways to do it if i mount the carb like most 2300 or 2100s on an angle i can weld a small extension i haveheard this works very well there asre no downsides on acceleration has anyone proven this the other option is mounting the carb with the fuel bowl facing the firewall but does anyone know if on hard acceleration will all the fuel go to the back of the bowl causing it to stall or on braking will all the fuel rush forward causing it to flood any inout is appreciated. just wanna get this done right the first time. measure twice cut once...
 
I mounted a 2GC on a 280Z log intake, sideways. We were able to tune it for the 2800cc Datsun six. It ran great and never had any problems starting, stopping, or in turns. I tested it hard and never had any problems with the carb. 8)

It will probably be fairly rich, right off. It can be tuned tho.
 
i got the whole setup done and hooked up today. the carb is a 2 jet (slightly bigger venturis than a 2g) however the adaptor they gave me which is for 2g and or larger 2bbl rochester was too small for the throttle platesa so with a dremel i bored out the hole until it fit bolted it all up and i after i bent the stock linkage rod and welded a small piece of steel plate to the throttle hinge on the carb it works perfectly. the carb had an rbs so the low end power is a marginal increase however the torque in second gear and third is a huge difference no trouble with air cleaner clearence. i didnt really have time to tune the carb to the t because its getting late but it does run very well at speed the small surge of the 1bbl is completely gone and the car accelerates smoother it also takes a lot less throttle to keep the car moving or get it going. it does stumble a small bit on sharp turns because of the angle. i gotta clean the carb up because it looks a little shotty cuz the carb has been in a shed since it was new.
 
i got around to doing some fine tuning today and the carb idles fantastic car doesnt missle or shake at all in gear or park. the onlky thing i have noticed is some saturation of the casting on ethe bottom right of the carb and top the top the bolt was loose so i think that took care of that but on the base its not leaking but the casting of the carb is moist color difference if you will the adaptor was a little small so the casting of the carb hung out causeing a vacuum leak because the passage that hung out went to the throttle bores to correct this i put a small piece of hard rubber under it and tightend the gasket so i dont think its leaking from there especially because my vacuum is not a problem.
 
You must log in or register to reply here.

Similar threads

9
All Small Six Looking for sources for small base 2GC
Replies
3
Views
403
benchracer
B
R
All Small Six New Starter Cautions!
Replies
5
Views
367
philford
philford
awasson
All Small Six New Adventures in electrics fans and inline 6’s
Replies
4
Views
262
sixtseventwo4d
S
6
170ci 1965 170’s equipped with automatic trans?
Replies
6
Views
1K
chad
chad
DON
All Small Six Oil pump/stud clearance issue
Replies
4
Views
1K
DON
DON
Back
Top