Rochester 2G

Hi fellas,
I decided I want to try to get more umph out of my carb. I have a chevy 292 motor, with a Rochester 2G 2 barrel feeding it. It is the small version, and was originally on a 2.5L engine I had way back in the day. I know it is too small for this engine, and I looked at getting the bigger 500CFM 2 barrel, but ran into a crap load of issues not the least of which is the price of a new marine carb, and the fact that I could not find an adapter plate for the bigger one to mate it up with the log style intake/exhaust manifold (this is off the old Mercruiser 165 I6). I may have found an alternative, in that my cousin had an old 500CFM 2G he had on a 350 truck engine that he did not want. I know the carb body can't be used because it does not have the overflow return and all for marine use, but I took out the venturi cluster, and the three valves in the bottom of the carb bowl. Can these be swapped over to the smaller carb to up the performance, or am I barking up the wrong tree?

Woof Woof............

There are several differences between carbs in my opinion.



Use the truck carb for a test!!

Plug all vacuum ports, do not use the overflow (JUST FOR TESTING)

If it works then you need to do some research for a different (correct) one for marine.

Look at bad v6 and v8 Marine motor, with either rochesters or the merc carb. They will be jetted and the cfm will be in line with what your motor needs.

so what your saying is you think it's too small the carb thats on it now. You think there is a difference in jets from the 6 to the 2.5 ?

And you want to get more hp but instead of installing a 4 barrel you want to put another 2cg on it ? Too much money ?

I guess this is gonna date me some but am i the only one that used to drill out jets a c--t hair ?

kghost,
In order to use the truck carb, I would have to rebuild it before I could even use it for the test. It was rusting away on a shelf in my cousin's garage and it is definitely not ready to run. And I repeat, I cannot mount it on the intake currently, because the throttle body on the larger 2G has a different bolt pattern than the adapter plate the small one is mounted on. If you take the adapter off, it has the bolt pattern underneath for a 4 barrel carb. Cannot find an adapter on ebay or craigslist. To Chiefalen, I have not read anything that says that you can't use the jets for the 2.5 on a 6 cylinder, but this is a 4.9L straight six. Basically, it is the same size cubic inch wise as a 305 or close to a ford 302. You couldn't use the carb from a 2.5L four cylinder on one of those could you? I am not necessarily against using a 4 barrel, but I want a balance between power and fuel economy. If this isn't possible, then I have to look at using a 4 barrel.

Balance between power and fuel economy???????????????

Its a frigin boat, there is no balance!!!!!

Also its a 30 + year old boat anchor.......

GEEEZZZZZZZZZZZZE

Take the adapter off and slap a 4 bbl on it and have fun!

Thats it !!!!!!! Listen no junkyard boat boneyards near you ?

You should get for 50 bucks one on ebay.

Side note here, i have more time nowadays i started looking closer at carbs, alot have a plugged hole high, and i wondered about that.

It would not take alot to adapt one to a marine overflow hose from a manual fuel pump. If electric the fuel pump you don't even need it.

Just sayin, got one laying around you have to see what this carb how rusted it was today i rebuilt for a robbins little mini bike. Runs great took about a hour.