Thread: What causes low rpm hesitation?

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If your tailpipes are that black you are running too rich. Makes me think that the primary jets are too big and/or the metering rods are too small. The lighter springs will cause the vacumn advance to come in sooner and with the weight of your car that's not necessarily a good thing. What size is the carb and what size are the primary jets? Much over 600cfm and you're over carbed. Are you coming to the Nats on Friday or Saturday?

The carb is a 1405 (600) and I could not tell you what size the jets are. The hesitation is in the accelleration part of the carb I think. It does it when I press on the trottle no matter what speed I am going. Yes I will be there on friday for the whole weekend, I can show it to you then and see what you think.

Excessive fuel pressure will also cause hesitation...... about all and engine needs is 4-6 pounds.... Weak springs can let the distributor advance at too rapid of a rate when you smack the throttle.... Along with the jets and metering rod isssues. Could be a number of things, Brick. What did you end up with for timing on the new engine????

Everything is stock as far as fuel pump but I did put in 3/8's line. The timing was about 4 after, I didn't have my glasses with me that day. My light is out now too, I need to get another one and re-time it. How much does changing the cam change the timing or does it?

I could be the springs on the metering rods. They might be lifting the rod out of the jet at idle. Really rich and gassy. Also if you can turn the idle screws in and out with no effect,your throttle plates are not adjusted right or metering rods again. Aren't edlebrocks wonderful

You can download a PDF file of the users manual for Edelbrock carbs at their site. www.edelbrock.com
I'm having the same problem with mine. I'm leaning toward the metering rods and jets. I put the elec. choke kit on my manual choke carb and I think I need to change the jets and rods also.
GaryB