I have a Holley 750 DP (4779-9) carb that I'm considering upgrading the main body in order to tune my idle. My AEM A/F gauge is showing that it's running very rich.
I've done the little piece of wire (.018") trick in the idle feed restrictor with very little difference. At this point, I feel that maybe replaceable air bleeds on the main body upgrade part could help (thinking larger outer bleeds will lean up the idle). Only that, but ditching the choke horn and better flow is a nice plus too.
I've been looking at the following part numbers and I can't decide which to use:
I consulted with both Holley and Summit, and they both say that I won't lose the timed vacuum port in the metering block with either of these upgrades. I just haven't found any evidence other than their word that this is true.
Here's my questions:
Have any of you done this main body upgrade and was there a benefit?
If you've done this upgrade, can you verify that the timed vacuum port still works?
Zinc or Aluminum?
If Zinc is preferred, anything wrong with the Shiny Zinc that's my preference?
Here's a video illustrating the A/F ratio:
Engine Specs: 360 with Comp Cams XE268H cam, 9.6:1 C/R, EngineQuest 318B Heads (means I have 1.6:1 Magnum Rockers), Edelbrock AirGap Intake, Dougs Headers, Custom X-Pipe, 4 speed, 4.10 gears, MSD billet with a 6A box. Timing at about 16 to 18 degrees (need to check for accuracy on that)