General Category > Quadrajet Carb Talk and Tips
Hesitation when taking off
Cliff Ruggles:
You mentioned swapping out the main casting.
Did you verify that ALL of the items were the same as the first one?
Lower Idle Airbleed?
Upper Idle Airbleed (if present above the DCR's)?
DCR the same size?
Idle tubes the same size?
Once fully warmed up if you tip the choke flap in or place your hand over it does the engine speed up and smooth out?....
Kavesh:
Hi Cliff, the float bowls are meant to be to identical. The only exception is that one was made by carter 29282 and the other Rochester. 7009282.
I did not verify anything I guess. I used all the internal parts from the other other float bowl. with the exception of the idle tubes. Are the idle tubes not the same on these units?
I am not sure what the DCR's are, sorry.
When I placed my hand over the carb when it was idling badly it made no difference to the idle, however now that I have swapped over the float bowl, when covering the primary side the motor want to die.
Kavesh:
Hi Kenth
So the mix screws were out 2 and a half turns on both and I tried opening them further but it made no difference at all.
I have not tried to attach the vacuum gauge recently as it seems I am chasing my tail!, yes it is an automatic.
I cannot advise on rpm either as my truck does not have a tach.
In any event I have not swapped out the float bowl, I am back with the Carter built unit. Base plate and airhorn are reused. All internals were also swapped except for the idle tubes. (How does one tell the size of the idle tubes?)
I have the idle mix screws set at 1 and 3/4 turns out, and the motor is idling fine, could not go for a drive as yet. I suspect the off idle hesitation may be back but can only confirm when driving. When I bump the accelerator initially it does not respond immediately on the second attempt it increases rpm faster. What causes this issue, no blockages found in any passages.
As my airhorn gasket was looking a little damaged, I decided to use 2 gaskets, one slightly thicker one and the original thinner one that was on the carb. Will this be fine or should I go back to a single gasket.
Cliff Ruggles:
Poor response when you push the throttle on the first attempt then improved on the second could be several things. Accl pump check ball leaking or the engine is "loading up" some at idle and needs cleared out.
I would NOT double up the gaskets or use one that wasn't in good shape.
I have .015" and .030" thicker main body to airhorn gaskets for the early units. A poor fit between the main casting and airhorn could be part of the issues you are seeing.
I suspect the carb is lean on the idle system contributing to the off idle stumble.
Idle tubes are measured using precision drill bits. A set with #61-80 will have the needed sizes......
Kavesh:
Thanks Cliff, I will go back to the single gasket on the airhorn. Will use the thicker of the 2.
I wish I was closer to the USA to pick up a new kit from you, but right now cost of shipping to South Africa is ridiculously expensive. It is sad that my current kit from you which has not seen much miles is getting ruined due to trying to fix issues as explained on here.
Without the precision tools would you say it would be a good idea to swap in the idle tubes between the 2 float bowl casting? Perhaps this will give me the response needed. (I am no carb expert so correct me if my logic is not right).
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