[Trent7276]

OK, I know this topic was brought up before, and I apologize for beating a dead horse but the answers weren't as clear to me as I'd hoped. I felt like I should do some testing so I did, and here is what I found and also hopefully my last question to the group on this topic!

I have a Mallory Unilite distributor. It has a vacuum cone on the side. 1971 400 engine with 12 deg advance. No pinging or detonation on pump gas.

Test #1 - I hooked this hose from the vacuum cone to the "always on" vacuum port on the front of my Edelbrock 1411 carb. When I do this I get great power in all ranges, shaky stumbling idle, and 15-16 hg on the vacuum test for that hose, with vacuum increasing as I slowly accelerate. The "stumble" directly shows a dip in vacuum pressure by about 1 - 2 hg, so it will bounce about every 2 -3 seconds from 16 or 17 down to 14 or 15 (hence the stutter I guess). Drivability is good.

Test #2 - I hooked the distributor vacuum hose up to my "not on at idle, but vacuum kicks in when RPMs increase" vacuum port on front of my carb, opposite the other port, and I plugged the other port. My idle speed dropped and I had to turn up the idle speed screw slightly to get it back around 900 rpm. Idle quality seemed much better, no stumble or at least very little. No vacuum reading at idle but it picks up to 15 and above when accelerating. Took it out for a drive, and primaries seems not as touchy, secondaries when they opened up at WOT seemed a little less powerful, still a kick in the pants but not as much it seemed...but I could be imagining this if in fact there is no difference between the two setups when at WOT around 3000 - 4000 rpm.

OK here is my question. Which setup should I be running?? What is the power and idle and fuel MPG advantages and disadvantages of each?? Thanks and I would be happy to supply more info if it will help settle this once and for all!

Trent
1968 Firebird 400, 4-speed coupe.