engine cutting out under load

[81K10]

Hi all, I'll try to explain the best I can...freshly rebuilt 350, performer intake, Rochester 4 brl carb.

Seems to idle smoothly but pretty rich, and while driving the engine often cuts out and then after a second or two with my foot off of the throttle the engine will cut back in. This will happen repeatedly once it starts, uphill or flat, and regardless of fuel level in the tank.
New plugs, wires, mechanical fuel pump, fuel filter, air cleaner.

Is this a carb problem or what do I need to look at?

Thanks in advance for you time.

Tony

[Irish_Alley]

Is your carb rebuilt?

[Lt.Del]

check for vacuum leaks.
check for back pressure (ie: clogged catalytic converter)
could also be accelerator pump on carb

[81K10]

the carb has not been rebuilt while I've had it (6 months) but ran well when first installed, Exhaust is brand new dual 2.5" manifold back through flowmaster 40's, no cats. Accelerator pump squirts fuel with the engine off.

where and whats the best way to check for vacuum leak?

thanks.

Tony

[Lt.Del]

idle your engine.  Spray WD-40 all around vacuum lines, carb gasket, intake gasket, etc... If rpm's go up, you found a vacuum leak. 

[81K10]

thanks. I'll try that and post what happens.

[topp]

Sounds like lack of fuel when you get on it.
Rebuilt motor, carb tuned for the pre-rebuilt motor-
Cutting out when getting under load...... leads me to believe you need to fatten the secondaries, and check the accelerator pump.

Prolly need more fuel than you did prior to the rebuild

[Irish_Alley]

a blown accelerator pump would cause that. have you had any backfires out the carb lately they will usually blow it depends on the type of carb and all

[kilam68]

Sounds like the problem I had.  After a lot of time and parts. I fixed it by changing the fuel strainer sock in on the fuel sending unit.

[81K10]

Finally had time to work on this...Sprayed wd-40 all over while idling and it had no effect on the idle, no backfires through the carb that I know of, Vaccuum lines are in good shape...Perhaps I should just buy a new carb since everything else on the engine is new. Might just bolt on a known running carb and see if that eliminates the carb itself as the problem.

I'll check the sock on the sending unit if the borrowed carb does the same thing.

[bobcooter]

Is it cutting at when you are going a constant speed? Or does it cut out when you mash on the gas peddle harder?

[Lt.Del]

fuel pump?

[TexasRed]

But he's got a new mechanical fuel pump. Those "usually" don't fail outta the box.

[Swims350]

had this problem on the 84's q-jet it was the carb starving the motor of fuel and only did it under load.

I'd try another carb or check the filter/strainer in the inlet of the carb, we did that and changed the pump, put in an in line filter and blew air back thru to clean the fuel strainer in the tank and still got nothing, no vac. leaks, complete tune up and all, ended up putting on an edelbrock carb I rebuilt and solved it for good.

[Irish_Alley]

i heard that a double pumper will solve the problem of when you mash the gas the fuel will be pushed to the rear of the bowl causing it to starve the motor for a sec