So that is the dual port vacuum advance version correct? If that's right, how are you hooking it up? The port closest to the dist open and the one sticking out to the ported source of vacuum on the carb?
Hey Franklin,
The short answer to your question is Yes. The Cardone 30-2671 has 2 ports on it.
I have a vacuum line running from the inline nipple of the vacuum diaphragm to the 'ported' nipple at the top of the Holley carb I am running. I have static (idle) timing set at 11° BTDC. Just as soon as I crack the accel arm on the side of the carb vacuum comes on and timing moves to 27° BTDC. With the accel arm on the carb moved to highway cruising RPMs total timing settles in around 38° BTDC. These #'s are in PARK sitting in the driveway, not out on the road. On the road driving, the 2.8 doesn't ping or do any other unwanted quirky stuff, it just runs real nice.
Hooked to manifold vacuum, with the engine fully heat soaked, it cranked right up and settled into a good idle. Timing immediately went to 27° BTDC. Raising RPMs to cruising speed, the timing settled at 38° total, just like with ported vacuum. I did have to back off the idle screw 1/4 turn to have the same idle speed as using ported vacuum. Using manifold vacuum, I did notice something that I had read about in vacuum sourcing post on the internet, and that was that engine temp dropped 5° degrees at idle while hooked to manifold vacuum.
On cold start, hooked to manifold vacuum, the engine would not catch and run, it just didn't want that much advance when firing off cold. With the engine warmed up, it never missed a beat on re-start.
On cold start, hooked to ported vacuum (which is 0 vacuum until the accel is cracked), one pump of the accelerator pedal, manual choke lever pulled to a point that the choke plate is maybe 1/4" from fully closed, and the engine starts immediately.
I have tried every combination of ported/manifold vacuum sourcing, along with capped/uncapped on the 90° nipple sticking out the top of the vacuum diaphragm and there were no changes in performance (I realize that the word 'performance' is subjective when talking about the 2.8) no matter whether the 90° was capped or uncapped. It just ran great.
The 38° total is my best guess due to the timing marks on the crank pulley topping out at 33°.
38° seems slightly excessive to me and would be easy enough to change if I chose to. We will see.
All of my tinkering has been done without the static timing of 11° BTDC being changed.
John