Hello, have a Holley 4 barrel carb older model. The car will start and idle fine but as soon as I rev it up then it idles super fast. It wont kick down or anything. It is also kind of backfire and popping. I have checked for vacuum leaks and messed with the accelerator pump adjustment. Kinda of at a loss. Any help would be greatly appreciated. Thanks
Carb help for Newbie,plaease!
- Thread starter Badfish1
- Start date
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ScampMike
Despicable Damn Yankee
choke adjustment needed? or maybe idle mixture. do you have return springs on the throttle?
71DodgeDemon340
Well-Known Member
Put a eddy on it lol
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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That's an easy one.
if the throttle is not hanging up, then the Tport sync is off.
Here's how this works. The engine won't idle fast enough, so the first thing a guy does is crank up the idle screw.If the timing is late, causing the slow idle in the first place, then the adjustment puts the throttle too far open. Thus the transfers are ready to flow and the vacuum advance may be operational. Then when you advance the throttle, the transfers start flowing, and with the additional advance from the can, the idle speed just hangs there.
The proof for this diagnoses, is while the idle is hung, interrupt the ignition, just long enough to return the rpm to around 600 and then turn the ignition back on. If the engine is then idling normally,as before, then the diagnoses is correct.
The cure is to restore the Tport sync, close the secondaries,crank in some advance, and start over.Once the Tport sync is set, do not stray far from that setting. To set the idle speed you will use timing and idle-air bypass(IAB).IAB is commonly provided by cracking the secondaries, adjusting the PCV flow, or drilling little holes through the primary blades.
The backfiring and popping are likely unrelated issues to the idle-hang up.
if the throttle is not hanging up, then the Tport sync is off.
Here's how this works. The engine won't idle fast enough, so the first thing a guy does is crank up the idle screw.If the timing is late, causing the slow idle in the first place, then the adjustment puts the throttle too far open. Thus the transfers are ready to flow and the vacuum advance may be operational. Then when you advance the throttle, the transfers start flowing, and with the additional advance from the can, the idle speed just hangs there.
The proof for this diagnoses, is while the idle is hung, interrupt the ignition, just long enough to return the rpm to around 600 and then turn the ignition back on. If the engine is then idling normally,as before, then the diagnoses is correct.
The cure is to restore the Tport sync, close the secondaries,crank in some advance, and start over.Once the Tport sync is set, do not stray far from that setting. To set the idle speed you will use timing and idle-air bypass(IAB).IAB is commonly provided by cracking the secondaries, adjusting the PCV flow, or drilling little holes through the primary blades.
The backfiring and popping are likely unrelated issues to the idle-hang up.
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