Stupid carby

Hello I have a stromberg 2 barrel carby which has been running like crap and making me very depressed. Basically what is happening is the engine seems to be running really smooth, strangely smooth, not lumpy at all and when I sit at idle the carby works for a while, but gets slower, slower and eventually dies. When it dies it drips fuel onto the manifold. What should I do to fix the problem? Anything short of putting the garden hose on it and using it as a sprinkler would be great. Cheers

 

This is , of course , an obvious problem . In Australia the carb is upside down and all the fuel drains out . If it were in the US I might suspect you have float problems

 

But of course.. I fixed this problem by putting wheels on the roof. I've maneuvered the float a few different ways but always ends up with the same result. The needle and seat seem to be sealing perfectly fine and float is currently sitting at the specified height. Curious.

 

Check the fuel pressure.

 

Pressure is tops, I put a new fuel pump on recently.

 

Fuel drips from where?

 

float not floating..?

 

It seems as though it is dripping out of the lower butterfly spindle on the left side of the car (Drivers side USA). The float floats fine. I can usually sort out a problem with a carby in no time but this has got me perplexed.

 

The pressure should be no higher than 3 PSI per carb. Also what kind of car? Is the tank higher than the carb? I have had this problem before. Turned out that in my model A with stock tank, under a full tank situation the weight of the gas pushed the gas past the needle/seat.

 

Verdict was a blocked idle circuit. As for the leaking? Needle wasn't sealing 100 percent and it was a leaky carb anyway. I have another question. Are all standard 750 cfm rochester quadrajets jetted much the same regardless of the engine they were originally pulled from? Does anyone know?

 

no, there is nothing standard about a q-jet. depends on the make and model of the donor car. q-jets are amazing animals if they're tuned in the hands of someone who knows them well... but they are a royal piece of shit otherwise.

 

The Rochester Q-Jet (my opinion) is the second finest street 4-barrel ever built.

That being said, Rochester built HUNDREDS of different versions, as the Q-Jet is versatile enough to use on many types of applications.

If migrating an original equipment carburetor from one application to another (any original equipment carburetor), for best results remember:

(A) Displacement of the two engines should not vary more than plus/minus 3 percent.
(B) Type of engine (oversquare, undersquare) should be the same.
(C) A carb designed for a manual transmission should not be used on a vehicle with auto transmission.

Violation of any of the above 3 "rules of thumb" will result in either carburetor modifications being necessary, or less than optimal performance.

These rules of thumb do not necessarily apply to aftermarket carbs which generally have a much lower (richer) A/F ratio.

Jon.

 

I don't suppose that Quadrajet carbs are marked in some way to indicate the make and model of the factory donor car? It would seem that using a used Quadrajet could a big crap shoot unless you are a experienced/trained carb technician. Really?

 

Hey Jasper, the only thing that will let the engine idle down until it shuts off is a vacuum leak. That is for sure, sun rises in the east kind of thing. If there is dirt in idle ckt then it wouldn't run at all, if it idles then slows down until it just shuts off it is sucking air from somewhere else than thru the venturii.

 

q-jets came in 2 sizes from GM 75o cfm for small blocks and 850 for big blocks. There is a number stamped into the driver side of the carb on the secondary side as an example=1753241.The first two numbers tell what division of GM the carb is from. Use this number at a parts house to get a rebuild kit. Always get a new brass float ,todays gas can eat into the plastic ones. Doug Roe had a book out on them that is still available. I use to run them in S/S classes and on the street.When set up properly they run great and get good fuel econmy. The biggest problem with old ones is leaking plugs on the bottom of the fuel bowl. The common fix for years has been to put fuel proof epoxy on the plugs when rebuilding them.

 

do yourself a favor if you're planning on messing with q-jetsm... get the book rebuilding and modifying the rochester quadrajet by Cliff Ruggles...

great book, well written and lots of information and pics... for the money, it cant be beat in my opinion