I have a ZZ3 crate motor in my '71 w/a 3.55 rear end gear. I purchased a Holley carb specifically tuned for the ZZ3-ZZ4 crate engines from Inglese Performance after reading about them in a Corvette magazine. Because it was built specifically for my motor, I assume the jets and accelerator pump as well as the power valve are correct for my application.

The car idles well and accelerates great. The problem I have is it bogs & hesitates at cruising speed. It never seems to act up as long as I am accelerating or decelerating. I have noticed it in the past, but it seemed more of an annoyance than a problem. Today, the engine completely died several times on the interstate when cruising at 3000 prm for about 10 miles. Once I pulled to the side of the road and let it sit for a minute or two, it would start right up, idle well & go for another 10 miles or so.

I revoved the gas cap thinking the car may be building up a vacuum in the tank. This did not help. It was way too cold for a vapor lock & my clear fuel filter showed no boiling or was not clogged at all. When the car began to die, I could push in the clutch & keep the engine running by pumping the gas, engaging the accelerator pump, but it would not pull the car. Because the accelerator pump would squirt, I assume that there was fuel in the bowl at the time. My carb has clear sight bowls and always appeared to be ok when I would get to the side of the road. Another thing that confuses me is that once I got off the interstate & away from long periods of constant speed, the car acted fine. Today was the first time I have driven the car on the interstate at all & I wonder if the problem has been there all along.

Also,by fuel tank is new and appears to be completely free of trash. I did not replace the long fuel line & did not install the carb, so I cannot say that there is no way it has trash in it. The fuel pump is a Holley that should flow more than enough fuel for my application.

I am planning to remove the fuel bowl & metering block to see if there may have trash in them. None of the trouble shooting guides I have seem to explain my exact situation. I have a basic understanding of Holley carbs but am in no way an expert. Any advise would be greatly appreciated.

Thanks.

 

sounds like a power valve problem,not the correct one or maybe the power valve restrictions in metering body are plugged. if not that install a inlne fuel pressure gauge to see if it changed when this happens:chevy


[Modified by clem zahrobsky, 3:04 PM 1/12/2003]

 

thanks for the advise. i read at a help site last night that a problem with the power valve could cause my problem. i removed the bowl & metering block today to see if there were any restrictions. it looked perfect inside. there was no trash at all. there was just a bit of the power valve gasket that protruded into the power valve opening. i trimmed it off. also, my fuel filter was more dirty than i had thought. i guess it was 50-60% covered in a silt-like substance.

also, i noticed that my pcv valve was not working right. i don't think it was the problem b/c it flowed all of the time instead of being restricted. let me know if any of these things may have contributed to the problem i was having.

i drove the car about 30 miles today & did not have any problems, but i drove a long way yesterday before anything happened.

 

Hello Adam,
I'm on the holley learning curve too but remember reading how modular it is and easy to troubleshoot. Don't know what type you have but in steady state cruise an incorrect power valve could be cycling do to vacuum/loads. Only remaining suspect parts are floats (and needle/seat), secoundary vacuum diaphram (if you have one), and maybe fuel filter.
On the good side carbs. are fairly cheap and a good spare would make a go or no go gauge for fuel vs. electrical troubles.
Good Luck :flag