Carburator Issues

[Will Fish]

I need to replace the carb on my gm 250 inline 6. I'm currently running a 2bbl rochester and have had nothing but problems. No choke and throttle will not come down to idle unless pull back quick, among others. I've swapped the carb out with the same rebuilt carb with same results. It just seems these engines do not respond well to rebuilt 2 bbl rochesters?

I'm going to bite the bullet and just buy a NEW carb. Looking for an upgrade to the 2bbl rochester. Any info on other Carbs would be great, including cfms, model, performance.

 

[gm280]

Re: Carburator Issues

Usually when you are having a problem with the throttle returning, there is a miss-aligned carb to gasket to opening issue. The butter-flies are hitting either the carb gasket or the intake opening...been there done that! If you seriously need to replace the carb for whatever reason, look at a two barrel Holly type. But realize that a new carb does not make a super powerful engine out of a low not so powerful engine...A total misnomer... You didn't specify what other carb or engine issues you are having so I can't provide any other help or ideas...

 

[Will Fish]

Re: Carburator Issues

The carb installed now has no choke at all in addition to not coming back to idle. Also 1 of the air/fuel adjustments are non responsive. I know going with a Holley or other brand will not turn my work horse 250 into a speed boat which I don't want. I just want everything working properly and fine tuned.

 

[gm280]

Re: Carburator Issues

Any time you have a non-responsive adjustment screw, be it air bleed type or fuel bleed type, there is a leaking issue with the carb or gaskets. And since you have already stated you are having throttle return issues, there is a problem. Look for a carb with the options you want but understand that installing a choke option will mean you have to either manually apply the choke or install a push switch for an electronic version. There are other choke options that depend on the heat from the exhaust to disable the choke after warm up to disable the choke condition but each choke type has its pros and cons. Once you understand those pros and cons make your selection. Also be mindful of the CFMs you need and keep it on the smaller size for better response. Contrary to what most think, bigger is not always better. So a smaller CFM carb will always work better and certainly be more throttle responsive then a big CFM carb… You can easily determine the CFM number by understand both the displacement (inline 6, 250 CID) and then realistic determining the max RPMs your engine can turn under load. Those two numbers will determine the total CFMs your engine can effectively use… Don’t go much over that number. Example; a 250 Cubic Inch Displacement engine turning at 4500 RPMs will use about 325 CFMs. So look for a 350 to a max of 400 CFM carb… And a progressive two barrel would be a great choice… :joyous: