Carb blowing fuel out air horn!!!!

[BS CUDA]

Ok guys need some help AGAIN. 1000 CFM Holly HP series is blowing fuel out the primary air horn. I have changed needle and seat as well as float and ensured floats are adjusted properly. Seems to only blow the fuel at higher RPM (5000ish - unsure exactly as tach stopped working when ammeter spiked last October) when warm. Fuel pressure set to 6 PSI - Holley electric pump with return to tank from regulator.

This thing is driving me crazy!!!!

[734406pk]

Blowing out fuel at 5000 rpm? Is this happening under acceleration only?

[brads70]

Vent whistle installed?  If so I've seen them sag and keep the float down making you think it's the needle and seat or excess fuel pressure problem. 

[sassygreen]

reversion. that is why stacks are 10 or 11 inches tall on old hilborn fuel injection units.

[BS CUDA]

Blowing out fuel at 5000 rpm? Is this happening under acceleration only?

Might not be 5000 but yes only under acceleration - I can reproduce it in the garage as well by revving it up.

[BS CUDA]

Vent whistle installed?  If so I've seen them sag and keep the float down making you think it's the needle and seat or excess fuel pressure problem. 

Those white rectangle items sticking out of the metering block? Yup they are there - never knew what they were called. Carb likely has less than 1000 km's on it.

[BS CUDA]

reversion. that is why stacks are 10 or 11 inches tall on old hilborn fuel injection units.

Seems this would be a very exaggerated example? This condition was not evident when they dyno'd the engine with this carb and they continually pegged 6000RPM.

Suggestions to prove or disprove this theory? When the car is being hammered I can feel as well as hear it going on as it sputters like it is hitting a rev limiter. I know it isn't hitting the limiter due to replication in my garage with the air cleaner off and seeing the fuel come almost pouring out the tubes.

[Skunkworks Challenger]

One or more intake valves not closing at high RPM?

[Chryco Psycho]

sounds like the float is not bouyant enough to regulate the flow so the pump is overpowering the float & overfilling the bowl

[HP_Cuda]

I would say either your regulator isn't doing the job all the time or your floats are set a bit too high.

Can you run the car up to 5k in the garage and watch it with a fuel guage. If you see the fuel pressure jump at 5k then you know what you have to do.

 

[734406pk]

Try lowering your fuel pressure to 5-1/4 to 5-1/2 psi and run it up to 5000 rpm. Check the fuel pressure gauge at that RPM to see if it remains steady. Is the fuel pressure regulator mounted on the fender or firewall (off engine)?

[BS CUDA]

Changed the float last Sunday - no change. Bought a new regulator on Monday and set it at 5 1/2 and still spewing fuel. Today I went ahead and changed the primary 50CC accelerator pump assembly back to the 30CC the carb originally came with and seems to be fixed now. Unsure why as the 50CC was on the carb at dyno as well. Also brought the regulator back up to 6 1/2 psi and still fine.

Still not confident problem completely solved as it was only 5C outside today and was low 20's when this problem was quite evident last couple weeks. Want to rule out heat as being a contributor.

Thoughts as to why the accelerator pump may have solved this fuel spewing issue?

Hopefully this is fixed so I can get the car into the engine rebuilder to fix the rear main leak that should have been caught on the dyno. Sure am getting tired of fixing stuff that shouldn't be broken.

[sassygreen]

Unless your engine is 500 cubic inches or larger, 1,000 cfm carburetor is most likely the problem. Try a smaller carb like a 780 or 750, for anything 440 or smaller.

[BS CUDA]

Unless your engine is 500 cubic inches or larger, 1,000 cfm carburetor is most likely the problem. Try a smaller carb like a 780 or 750, for anything 440 or smaller.

500CID - 620 HP and 620lb ft - 1000 CFM is right on the edge.

[734406pk]

Changed the float last Sunday - no change. Bought a new regulator on Monday and set it at 5 1/2 and still spewing fuel. Today I went ahead and changed the primary 50CC accelerator pump assembly back to the 30CC the carb originally came with and seems to be fixed now. Unsure why as the 50CC was on the carb at dyno as well. Also brought the regulator back up to 6 1/2 psi and still fine.

Still not confident problem completely solved as it was only 5C outside today and was low 20's when this problem was quite evident last couple weeks. Want to rule out heat as being a contributor.

Thoughts as to why the accelerator pump may have solved this fuel spewing issue?

Hopefully this is fixed so I can get the car into the engine rebuilder to fix the rear main leak that should have been caught on the dyno. Sure am getting tired of fixing stuff that shouldn't be broken.

That is strange. I'm not sure it's fixed either.  Pump volume shouldn't have anything to do with vent overflow, but time will tell.