GMC 305 v6 Holley 500 swap woes

[AngryPirate]

Originally Posted by MikeN

From looking at the photo, it looks like maybe you have an unused and unplugged vacuum port? Make sure any ports you aren't using are plugged. Also, if the vacuum advance is causing your idle speed to be too high, switch to a ported vacuum source. This will be the port high on the metering plate in most cases on a Holley.

Checking the float level is vital - fuel should just barely dribble out of the hole with engine idling.

Finally, you'll need to adjust the accelerator pump cam clearance, and possibly the squirter size. You can google how to do that.

All that said, it's CRITICAL to make sure you have no vacuum leaks,. so gotta make sure your seal/gasket to the intake is good.

"it looks like maybe you have an unused and unplugged vacuum port"
There isn't but always worth mentioning.

"Checking the float level is vital - fuel should just barely dribble out of the hole with engine idling."
This was a good call. It was waaay too low. Adjusted. Thanks! And thanks also geezer#99 for this suggestion.


"Finally, you'll need to adjust the accelerator pump cam clearance, and possibly the squirter size. You can google how to do that."
I'll check this. I believe it's the nyloc nut with the spring on the throttle linkage side of the carb next to the bowl.

"It's trial and error as to which works best in most cases."
Noted. I'll try the other vacuum port on the back of the carb as well as the one on the intake manifold. The intake manifold and back of the carb vacuum ports are huge compared to the hose size that goes into the distributor.

Thanks again for the insight and suggestions!

I'm now dealing with a spark issue that started while messing with the carb. I think the Pertronix electronic ignition (points replacement) died from the non-stop starting I was doing while trying to get the carb set up.
Coil is good (also got a new one to be sure, but the resistance seemed fine on the old one), ignition switch is sending power and neg side of coil outputs voltage while starting.