slight off idle stumble and changes for tip in?

[starks]

Hi guys in Brisbane, Australia. Got a quaddy on a 1976 Holden Hz ute running a holden 308 v8 (5ltr) and a T700. Carb # 17056280. Here theyre known as a 602, not sure what GM Australia got them off, Buick I think, but theyre the factory carb for this car and run the baseplate apt.
I dont have all the specs on the carb but factory ran a 71 jet with 50-51 primary rods and cx ct or dp secondary rods on usually an M hanger. A few differences depending on performance or economy set up but my understanding is it was an over all lean arrangement.
I have rebuilt the carb following cliffs book but have not altered the idle air bleeds from factory.

The engines rebuilt with a cam one size bigger than factory, edelbrock intake, mild head porting, bottom end is 30thou over and dual exhausts.
I was advised factory set up was too lean and to run 73 jets with 43 rods and DA secondary rods on a K hanger. Was way too rich and gave me spark plugs as black as the ace of spades. I changed back to factory 71 jets but with a 44 primary rod.

Driving the car at WOT acceleration from a standing start runs great and pulls hard. General cruising is good and the throttles responsive. Just one issue when accelerating normally from a stand still theres a slight off idle stumble which Im not sure which direction to go to look at rectifying.
Also during tip in procedure with the baseplate apt set 2 turns up from being bottomed out there was no change in rpms giving the engine slight choke but rpms increased significantly once removing a small hose. Or plugged vac outlet in this case. Ended up with the apt only a qtr turn up from bottoming out and with vac port unplugged still increased in rpms but slightly. So my understanding is the primary circuit is still to rich? Im thinking I should be going back to a fatter rod size? I have a pair of 48o rods here that have a step in them or a pair of .050s that are tapered but have a 0.036" tip rather than .026". Would one of these be better?
In regards to float level factory service manual states .46" or 11.9mm for we that got stuck with the metric system. These seemed a little low or is this an ok float level? Its set at .400" now after seeming to be keeping the primary air bleeds wet at 1/4" and seems ok. Any thoughts?

[starks]

Ok, was mucking around with her last night and realised I had made a mistake. Even though it's a later model carby it still uses the old metering rods. at least that's what was in there. How common was this?
Ive used the later ones thinking post 75 they will be the newer ones but measured the originals and they're longer.

And secondly will the .030 size small rods apply still with this set up? As I will have to buy the older style now to suit this.

[Cliff Ruggles]

The later model carburetors with the APT system just in front of the power piston came in two styles, single main airbleed, and two pairs of main airbleeds.   ALL of them use shorter metering rods than earlier designs.  In almost all cases, the single MAB models will use "M" series metering rods with .036" tips.  The two main airbleed designs used several types of metering rods, all with .026" tips, "K", "L" and "P" were the most common.  They vary in dimensions on the upper section, and some "step" down to the tips and others are tapered between sections.

The later carburetors are fine tuned on the primary side by using the APT system. 
If you are "custom" tuning, determine the best jet size first, then go after the best metering rod.   There is no need to pull the airhorn to make tuning changes once the carb is set up with the correct parts.

I use and prefer the tapered late style metering rods, as they provide a broad range of adjustment, even if raise them up to the tapered section between sections.

Without knowing exactly what carburetor you are working with, and all it's specifics, impossible to give any specific advise on jet/rod combinations.

I will say that .400 is a low float setting, I prefer closer to .250-.280" for those units, and the fuel level in the bowl can have a significant impact on tuning with any given jet/rod combination.  It will also effect idle fuel delivery.....Cliff