440 superbird stumble
12-21-2010, 02:22 PM
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440 superbird stumble
New to forums. Bought my first mopar - 70 superbird 440 4speed. Restored all stock. Engine stumbles off idle. Idle pretty lumpy. Had carb rebuilt, checked timing etc. my local guy thinks somone put in a race cam as there is little vacum at idle (6lbs) and it runs better oncve the revs are up. I'm mostly a GM guy and am stumped. Any other ideas what this could be before i go pulling the cam? beautiful car but the thing runs like poop
01-27-2011, 05:39 PM
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I am very interested in seeing the answer to his question as my car is having a similar problem. I have a 74 Challenger with a 360. It hesitates just off idle as if it weren't getting enough fuel. The carburator was rebuilt recently. I have MSD distributor and computer. I have played with all the different spring settings in the distributor for different advances. I assure you that my 360 has not been modified with a different cam or any other internals. My choices are either accelate very very slowly or accelerate fast. You can guess which I have been chosing.
yellowbirdted, if you find out the answer, PM me.
yellowbirdted, if you find out the answer, PM me.
02-04-2011, 07:10 AM
#8
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HI,
is it a Holley carb
if so and you only have 6" of vacuum @ idle you will need to change the power valve to a 2.5 Holley part # 125-25
The stock PV is a 6.5 that would need at least 13" of vacuum
also make sure the acc. pump is set correctly
Look down in the carb without it running
move the throttle and see if the two sprays of fuel shoot as soon as the throttle moves
if it is not instant back off the nut on the pump arm 1 full turn counter clockwise
then check it again
do this until it is instant
@ wide open throttle you should be able to push the pump lever into the dia. housing about .010"
to.015" just so it is not bottomed out at wide open throttle
If it is a dbl. pump do the same thing on the sec. pump
but it should spray as soon as the sec. starts to open
Try all of this it should help
Thanks Ricky R Holley tech service
is it a Holley carb
if so and you only have 6" of vacuum @ idle you will need to change the power valve to a 2.5 Holley part # 125-25
The stock PV is a 6.5 that would need at least 13" of vacuum
also make sure the acc. pump is set correctly
Look down in the carb without it running
move the throttle and see if the two sprays of fuel shoot as soon as the throttle moves
if it is not instant back off the nut on the pump arm 1 full turn counter clockwise
then check it again
do this until it is instant
@ wide open throttle you should be able to push the pump lever into the dia. housing about .010"
to.015" just so it is not bottomed out at wide open throttle
If it is a dbl. pump do the same thing on the sec. pump
but it should spray as soon as the sec. starts to open
Try all of this it should help
Thanks Ricky R Holley tech service
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