Weber DCZ6 Flat Spot

[tinbender]

I got the accelerator pumps working on my 330GTC and am now driving it. It has a stumble or flat spot when you accelerate from a steady speed. It is not a large stumble, just slight, and if you give it more gas it accelerates like it should. I am thinking something else is gummed up in the carbs. Any suggestions?

Thanks,
Terry

[DWR46]

Terry: Take out the Idle Jets and make sure they are open. Tell me what size they are. Today's fuel causes engines to run about 14% leaner than the fuels of the 1960s. You probably need to go up one size in Idle Jet. The Idle Jets effect the mixture quite a way up the rev range under partial loads.

[tinbender]

All of the idle jets appeared to be open. They are all marked 60.

[DWR46]

Terry: That is what I expected. Call Pierce Manifolds and get a set of 65 Idles. I end up running 65's in all the DCZ's today.

[tinbender]

Dyke,
I installed the 65 idle jets and I cannot tell a difference. The stumble is still there. It feels like it is running out of gas, but when you give it more throttle it pulls fine. Do you have any suggestions?
Terry

[DWR46]

Terry: Puzzling, almost every time larger Idles cure the problem. Hard to diagnose a drivability problem over a computer. Are the carbs correctly synchronized? Is the linkage set up correctly? Good spark plugs? Good plug wires? Do the pump jets squirt fuel quickly as soon and the throttle is opened? Plugged fuel filters? How much fuel pressure at the carbs? And on and on.

[John Vardanian]

While cruising, is there a "sneezing" from the carbs when you press the gas pedal? I had this issue.

john

[tinbender]

Dyke, yes so much to check. John, it does do that occasionally.
The car ran great, then it sat for a year or so and now it is having this problem. I don't think the carbs would have gotten out of synch or the linkage to have gotten out of whack from sitting. I am trying to figure out how to check the fuel pressure. I have checked the plugs and they look good.

[DWR46]

Terry: What size Main Jets?

[John Vardanian]

Speaking from my experiences, the accelerator pumps cannot be effective if linkages are set not right.

john

[tinbender]

Dyke,
The mains are 1.30. I pulled them all and it is possible that 2 or 3 had a slight build up in them. I cleaned them and reinstalled. I could not unscrew the jets from their holders. I broke a small piece off at the screwdriver slot on 2 of them and stopped trying after that. I have not had a chance to drive it to see if any change.