Holley carb issue or am I just and idiot? Ok im helping a friend with his 400 swapped S10. Im an EFI guy and dont have alot of carb experience. We are having an issue with the vac advance on his Holley 750. It would make since to me that on the timed vac port on the metering block should NOT have vacuum at idle?? Am I thinking correctly on that? I have not put a guage on it but it feels like its pulling as hard as the full vac port at idle. We have the timing set at 14* with the vac advance unhooked and plugged in at an idle it jumps to 35* which im thinking is full advanced. What could possibly be causing my timed vac and my full vac to be the same? Could it be the metering block gasket or is there something else im missing? Any help would be greatly appriciated. Thanks in advance!! |
Re: Holley carb issue or am I just and idiot? The ported vacuum will not have vacuum at idle. Holley carbs have several ports (depending on the model). Only one is ported vacuum on my 4150 style carb. |
Re: Holley carb issue or am I just and idiot?
Originally Posted by skinny z
(Post 4981994)
The ported vacuum will not have vacuum at idle. Holley carbs have several ports (depending on the model). Only one is ported vacuum on my 4150 style carb. |
Re: Holley carb issue or am I just and idiot? I reread your post and am checking out the Holley website for some info. Do you have a model number? Have you checked for another timed/ported vacuum source? |
Re: Holley carb issue or am I just and idiot?
Originally Posted by skinny z
(Post 4981999)
I reread your post and am checking out the Holley website for some info. |
Re: Holley carb issue or am I just and idiot? Yes, some models provide a timed port on the metering block. Mine is in the carb base. I would think that if the metering block port is delivering full manifold vacuum, then there's an internal leak. Perhaps the carb isn't as fresh as it could be? |
Re: Holley carb issue or am I just and idiot?
Originally Posted by skinny z
(Post 4982011)
Yes, some models provide a timed port on the metering block. Mine is in the carb base. I would think that if the metering block port is delivering full manifold vacuum, then there's an internal leak. Perhaps the carb isn't as fresh as it could be? |
Re: Holley carb issue or am I just and idiot? Above the throttle blades would be timed/ported vacuum. Below the blades is full vacuum. Get the part number from the choke horn. The small amount or research I've done says that not all models have a ported vacuum supply. I can't confirm that however in a pure racing application, the vacuum advance is often excluded from the setup. A part number will get you to a decent diagram. The rest is easy. After 8 years and liitle use, I suspect it may need a refreshing anyway. |
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